STARTUNEDInformation for the Independent Mercedes-Benz Service ProfessionalMay 2012 U.S. $6.00 €9.00 Volume 12 Number 2CARBON FIBER REPAIR TEMPERATE CLIMATE THROTTLING AWAY ABCs OF SUSPENSION V ^ J Mercedes-Bl
FIRE... .. on all eight with www.startekinfo.com.Mercedes-Benz USA Dealer Workshop Services is the source for all the technicalinformation needed to support, service, and maintain Mercedes-Benz vehicles.Mercedes-Benz workshops rely on DWS products and services for getting jobsdone quickly and more efficiently. Our products include: STAR Teklnfo with WIS-net (Workshop Maintenance Manuals and Sheets Information System) STAR Service Manual Library CDs Electrical Troubleshooting Manuals WIS and DAS software updates Installation Instructions Star Diagnosis System (SDS) Technical Bulletins Operators Manuals and COMAND Manuals Campaigns Mercedes-Benz Equipment Mercedes-Benz Special Tools Inventory of technical publicationsSTAR TeklnfoDealer Workshop ServicesEngineering Services, Mercedes-BenzMercedes-Benz USA, LLC.
TO OUR READERS: IN THIS ISSUEWelcome to STARTUNED, the magazine for independent servicetechnicians working on Mercedes-Benz vehicles. Your Mercedes-Benz dealer sponsors STARTUNED and provides the information 4 THROTTLING AWAYcoming your way in each issue.Mercedes-Benz wants to present the information you need to know Mercedes-Benzs pursuit of safer vehiclesto diagnose and repair Mercedes-Benz vehicles accurately, quickly incorporates individual systems workingand the first time; text, graphics, on-line and other technicalsources combine to make this possible. in concert to control speed, handling,Feature articles, derived from approved company sources, focus on and stopping. One critical part of this isbeing useful and interesting. the Electronic Accelerator. Heres how itOur digest of technical information can help you solveunanticipated problems quickly and expertly. works and how to fix it.We want STARTUNED to be both helpful and informative,so please let us know just what kinds of features and otherdiagnostic services youd like to see in it. Well continue to bringyou selected service bulletins from Mercedes-Benz and articlescovering the different systems on these vehicles.Send your suggestions, questions or comments to us at: 12 THE ABCS OF A TAUT SUSPENSIONSTARTUNEDOne Mercedes Drive Mercedes-Benz has always beenMontvale, New Jersey 07645 synonymous with agile handling, a stablePhone: 1 800 225 6262, ext. 7112E-mail: firstname.lastname@example.org feel, and compliant suspensions. Active Body Control is one way the companySTARTUNED is a publication of Mercedes-Benz USA, LLC ("MBUSA"). No part of thismagazine may be reproduced without the express written permission of MBUSA. brings these attributes into modern times.Editorial and Circulation Offices: 134B River Road, Montague, NJ 07827.CAUTION: Vehicle servicing performed by untrained persons could result in serious injury tothose persons or others. Information contained in this magazine is intended for use by trained,professional auto repair technicians ONLY. This information is provided to inform these techniciansof conditions which may occur in some vehicles or to provide information which could assist themin proper servicing of these vehicles. Properly trained technicians have the equipment, tools, safetyinstructions, and know-how to perform repairs correctly and safely. If a condition is described, DONOT assume that a topic covered in these pages automatically applies to your vehicle or that yourvehicle has that condition. STARTUNED is a registered trademark of MBUSA. 20 ABC SERVICE BASELINES Some practical points on the fundamentals.Group Publisher Contributing EditorChristopher M. Ayers, Jr. Tom Nashcayers@automotivedatamedia.com email@example.comEditorial Director MBUSA Technical Content AdvisorBob Freudenberger Donald Rotolobfreud@automotivedatamedia.com Donald.Rotolo@mbusa.comContributing Editor MBUSA Project Manager 22 TEMPERATE CLIMATEBob Chabot Adam Green With summer coming, youd better firstname.lastname@example.org email@example.com sure youre up-to-date on Mercedes-Contributing Editor Art Director & Circulation Mgr.Kerry Jonsson Christopher M. Ayers III Benz A/C service so you can keep firstname.lastname@example.org email@example.com customers in the Temperate Zone. Visit us at our web site www.MBWholesaleParts.com to view this issue and all past issues of StarTuned, along with a wealth of information on Genuine Mercedes-Benz Parts. 30 ARE YOU READY FOR CARBON FIBER REPAIR? To locate a Mercedes-Benz dealer near you, Carbon fiber parts will be in certain 2012 go to www.mbusa.com. Mercedes-Benz production series vehicles.
It all started with Mercedes-Benz in conjunction (Electronic Gearbox System) to co-operate in thewith the Robert Bosch Corporation in the mid- control of the vehicle when traction is suddenly lost.1980s. The companies worked together to develop In following years, the suspension computer of thea CAN (Controller Area Network) that debuted in chassis CAN was added, and ESP (Electronic Stabilitythe early 90s on the 140 chassis. CAN allowed Program) combined the drive CAN and chassis CAN.individual system control units, such as the ME (Motor By incorporating an electronic throttle system thatElectronics), ABS/ASR/BAS (Anti-Lock Brake System/ reads inputs from various sensors and modules, theAnti-Slip Reduction/Brake Assist System) and EGS drivers control can be enhanced, and traction is restored by closing the throttle until the tires regain their grip on the road. The Electronic Accelerator continues to open the throttle if input indicates that the driver still wants to accelerate. An added feature is that the electronic throttle can also handle cruise control functions and idle speed. No longer was a separate cruise-control actuator and idle speed motor needed to maintain vehicle speed and engine idle speed, respectively. The Electronic Accelerator can be commanded to open to maintain the selected speed. While this adds complexity to engine management, in another way it also streamlined it. With all of these control units on a CAN, the self-diagnostic system can monitor all inputs and outputs and display them in diagnostic software. In earlier years, you would have had to interrogate each system for DTCs (Diagnostic Trouble Codes) and manually check the signal values at each input and output to diagnose a problem. Now, the Mercedes- Benz SDS (Star Diagnostic System) allows you to look at the data on the CAN, saving time if you have to isolate a problem. You can and should interrogate the EA system with your SDS. If in addition to using SDS, you want to manually check signals at the control module connector, please remember that damage to the wires, connectors, or pins will most likely require that the entire harness be replaced. If the computer-controlled system sees any abnormality with EA inputs or outputs, the control unit enters a "limp home" mode and prevents the throttle from opening and the vehicle from accelerating. Many safety measures were incorporated into EA hardware and logic. The first item you need to know about is that there is a redundant system on later models just as you have on an aircraft. Two sensors perform the job of one so they can crosscheck each other. INPUTS In order for an EA system to work, it needs to know what the drivers intentions are, and this is accomplished by means of sensors that report on the Mav 2012 5
position of the gas pedal. In the early 140 chassis these Above: The first Electronic Accelerator design hadsensors are mounted in the EA unit (throttle assembly) a conventional cable at the throttle assembly, butbetween the MAF (Mass Air Flow) sensor and the it only drove a sensor in the assembly. Here is theintake manifold. Linkage from the pedal runs all the second-generation Pedal Position Sensor. A cableway up and out to the EA unit, but there is not a direct still drives it, but it has two potentiometers toconnection to the throttle plate. Instead, the linkage indicate the pedal position.moves the pedal position sensor. The EA control engine, and the left throttle feeds the right bank asunit processes the signals and opens the throttle by they cross each other through the intake manifold.providing power and ground to a two-wire DC motor.As the motor opens, a second throttle position sensor Starting in the 96 to 97 model years, the HFMchanges the signal voltage. This sensor lets the control (Hot Film Mass) air flow fuel system was upgraded tounit know what the actual throttle position is. the ME (Motor Electronics) system. This had separate pedal position and throttle-position sensors. The For safety, there are two idle contacts in the throttle throttle-position sensors are still in the throttle bodyassembly. These switches indicate when the pedal is assembly, but the pedal-value sensor is mountedin the closed position. One switch is normally open underneath the hood and is driven by a throttleand the other is normally closed with the throttle cable. There are now two sensors in the pedal-valuepedal released. When the pedal is applied, the two sensor assembly. They are both still three-wire units,switches change states -- the open switch closes and and they have individual five-volt references, signalthe closed switch opens. If one switch were to send voltages, and grounds. The voltage increases onan implausible signal, the other would take over, but both signal lines, but at different rate. The #1 pedal-the throttle would enter a power-reduction mode, position sensor signal voltage is roughly double that ofand DTCs would set in multiple control units. There the #2 APP (Accelerator Pedal Position) sensor. Withis a clutch that decouples the throttle motor from the a closed throttle, you may see .18v on the #2 and .28vthrottle plate shaft so if the system were to have a on the #1 sensor. The sensor signals are sent to themajor problem the throttle plate will not be opened ME control unit, which commands the throttle motorand the vehicle will not accelerate. In the case of the to open.M120 engine (early V12), the right throttle body isthe main unit that has the pedal position sensor in it. If the voltages are off by as little as .1 volts, a codeThe right throttle assembly feeds the left bank of the will flag and warning lights will illuminate in the lercedes-Benz StarTuned
• 5.0 • V 4.038 3.038 2.038 V 1.038 50 0.033 4.0-0.962 3.0-1.962 2.0•2962 1.0 n-3.962 CO-4 96% -1.0 00 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 18 2.0 Sds Ed777/s graph of the Pedal Value sensor shows APP # / starting off at around 0,3V and increasing to over 4V. APP#2 starts off at a slightly lower voltage and only increases to about 2.5V you would set a code and engage the limp-home mode because the idle switch would still indicate idle. There is a second Hall-effect type of APP. The connector is slightly different with two squared off corners. The same voltage readings still apply even with the different connector design. Starting with early- to mid-2000 211 and 220 chassis models, the accelerator pedal-position sensor is mounted directly on the pedal. This must be replaced as a unit. It still has two pedal-position sensors in it. It is a six-wire assembly with two five-volt references, two signal wires, and two grounds. The signal voltages are roughly the same as on the previousTake a close look at the EA harness connector. A design. Pedal-value sensor #1 starts off at about .35problem here may be the cause of an intermittent volts with the throttle closed and will increase tothrottle code and the customer complaining that the approximately 4.5 volts at WOT (Wide Open Throttle).engine goes into limp-in mode. Corrosion at the pins Pedal-value sensor #2 will start off at about .18 voltscan change the voltage signal enough to set a code. and increase to about 2.3 volts at WOT. In the serviceinstrument cluster. The two sensors cross-check each bay, do not expect to see these voltages wide-open.other. If one sensor sends a bad signal, the limp-home With the engine not running, the throttle will only bemode will give you up to 60% throttle opening, and commanded open part of the way. Keep that in mindresponse is slowed down. If both signal voltages are while checking the system.incorrect compared to one another the engine willonly idle. There is also an idle switch on the pedal. Changes have also been made on the actuator side.The ME control unit expects the pedal sensor to be No longer are there closed throttle contact switches inat minimum signal voltage when the idle switch is the actuator. Only the signal voltages from the motor-closed. If you were to move the APP sensor manually, position sensors are used to calculate throttle plate May 2012 7
JtaMMinnrifi JtM^: 0tf^nmmA close look at the signal voltages of the APP sensors in the throttle assembly shows the upper tracestarting off at over 4V with the key on and the lower trace starting off under one V. Toward the end of thepattern, under acceleration, one signal voltage decreases and the other increases.position. These have a six-wire connector. Two wires •~:fi^^0r^^supply the DC reversible motor to open and close thethrottle. The other four are for the position sensors.They share a five-volt reference and a ground, leaving SKSHpP^^ ^ • i 7mtwo signal wires. Throttle sensor #1 starts off at ^^kapproximately 4.3 volts, but this signal decreases asthe throttle plate opens. At WOT, you should see about.5 volts. Throttle sensor #2 starts off at about .35 voltsand increases to approximately 4.3 volts wide open. I *The voltages cross-check one another. Theoretically,both signal voltages should add up to about five volts Iin all throttle positions. 1 •^jdjl • These input signals are sent to the ME control unit, which processes them to control idle speed, cruise WK r * # M control, and rate of acceleration. In reverse gear, the rate of opening is slowed relative to pedal movement. It can also close to reduce engine power if signals come in on the CAN indicating that traction has been • .•"• lost. This reduction in power helps the tires regain their grip. iME is also in charge of all the limp-home strategies, and monitors the messages on the CAN Carbon can build up on the throttle plate and in from the ABS/ASR/ESP and other modules that the bore. The ME control unit will adapt by opening may affect power application. When the EGS (a.k.a. the plate to maintain idle speed. If the battery goes transmission control module) reports a shift, the dead, this adaptation is lost and the engine may not ME will retard ignition timing to help with smooth idle properly. After cleaning the throttle body, you shifting. It also monitors the amp draw of the throttle may have a high idle, so clear all adaptive strategies. 8 Mercedes-Benz StarTuned
actuator motor. If the throttle is will only allow the engine to rev You can also look at idlesticking or binding in the throttle to 1,800 rpm, maximum. Idle adaptation under "Actual Values"bore, ME will flag a code and go speed will be set at about 900 rpm with your SDS. These numbers showinto limp-home as well. using the injectors for control. If a if the ME control unit is opening the mechanical fault is determined by throttle to compensate for a low idle We already described the limp- the actuator, a safety fuel shutoff speed, or closing it to compensatehome mode of the pedal-position program is activated and the for a small vacuum leak.sensor: If one potentiometer injectors will stop delivering fuel atproduces an implausible signal, 1,200 to 1,400 rpm. There are no special proceduresyou will have a maximum of 60% when servicing either the pedalthrottle opening. If both sensors Cleaning the throttle plate and position sensor or the throttlesend problem signals, you will be bore has become part of a regular actuator other than the normalizinglimited to idle speed only. There tune-up, but is even more important of the throttle actuator. Eachare slightly different fail-safe today than it was. If carbon component should read the correctmodes for the actuator. If one deposits are present, the throttle signal voltages once plugged in andsensors signal is inappropriate, plate may stick, setting an actuator installed properly. Of course, eachthe throttle opening is once again code. Do not spray the solvent down component is relying on a stablelimited to 60%. However, the second on the throttle plate as it can work five-volts reference and groundsensor in the actuator and the its way into the motor assembly (both provided by the ME) to makeMAF sensor are used to command and damage internal components. the correct signal voltages. Youthrottle position. If both throttle Spray it on a rag and, with the key should always verify the five-voltsensors send faulty signals, or the off, wipe away the buildup. This reference and ground with yourtwo voltages do not correspond to will only help if you have a throttle DMM to make sure you do not haveone another, a spring capsule is actuator code. If there is a problem any wiring or control unit problems.activated and throttle opening is with an actuator, specific limp- There are also safety switches inlimited to 10 to 12 degrees. This home modes are engaged. the actuator. They are the ones that indicate that the throttle is closed The ME control unit is capable and at the idle position. The ME of learning if the throttle plate puts out a 12-volt reference that the is restricting air flow at idle and switch either grounds or not to let gradually opening up the throttle the computer know the vehicle is to compensate, which is known at idle. With the connector at the as idle adaptation. If the battery actuator unplugged, you should were to go dead, the ME may forget measure the five-volt reference and these adaptations. two 12-volt references for the closed This could cause a low idle speed, throttle switches. or a deceleration stall after the battery has been recharged. You Knowing the different limp- can simply clean the throttle plates home mode strategies coupled with to restore a normal idle. Throttle the use of your SDS (available for plate adaptation will have to be purchase from Mercedes-Benz, see performed after a dead-battery www.startekinfo.com) will help incident, or whenever the throttle reduce your diagnostic time and,If you have a hard code for the assembly or the ME control unit has more importantly, assist you inactuator or throttle position been replaced. You can perform the making a more accurate diagnosissensors, check the wiring harness throttle relearn with your SDS (Star of this critical system. Yourfor physical damage Unplug the Diagnostic System), or by simply customers rely on you to provideconnector and check the voltages leaving the ignition key on with service worthy of their Mercedes-on the harness side. Here we the engine off for 90 seconds. You Benz vehicles. This dedication tofollowed the harness and found should hear the throttle actuate as their safety and well-being willmultiple broken wires. the throttle body is being adapted. keep them coming back. | May 2012 9
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The ABCs of a TautSuspension^ 1 Mercedes-Benz has always been synonymous with agile handling, a stable feel, and compliantsuspensions. Active Body Control is one way the company bringsthese attributes into modern times.
Think of Mercedes-Benz and you may envision afull-size S-Class. Its compliant ride makes easy work oflong trips. The driver would want to feel the feedbackof a taut suspension, but not so stiff that her or shefeels every bump. Or, you may picture the SL-Class.An SL owner may want a stiffer suspension for carvingthrough winding roads. In either case, handling wasone reason they purchased a Mercedes-Benz. TheABC suspension system provides the best of bothworlds. With it, the driver is in greater control of thevehicles ride than was ever before possible, and, wherenecessary, the ABC control unit reacts to conditionsand makes adjustments accordingly. ABC is optional onthe S-Class, but standard on some other models. Active Body Control is aptly named because it is"active." Like any computer-managed system, it hassensors that read the environment around it andpass this information on to a control unit. This isprocessed with digital logic and decisions are madeon how to best to control the vehicle, commands aresent to accomplish that, and this all occurs withinmilliseconds of input changes. Even if the driver is unaware of changes in roadconditions, or the level of cornering power thatsnecessary for the way the car is being driven, ABCassists in maintaining stability. It is an electro-hydraulic system that directs pressurized fluid toindividual strut assemblies to control adjust vehiclelevel and suspension compliance.THE HEART The hydraulic pump is the heart of this system.It is capable of generating over 3,000 psi of force tosuspend the vehicle. This is an important factor toknow during service. If you are going to be removinghydraulic lines or components, you will need todepressurize the accumulator first. You can performthis task with your SDS, available for purchasethough Mercedes-Benz. Contact your dealer, or goto the Mercedes-Benz service information websitewww.startekinfo.com. The power steering system shares the same fluidsupply and pressure to operate, so when theres a problemcheck there for leaks as well. These pumps should not beallowed to run dry. If they do for more than four seconds,internal damage may occur. Fill the reservoirs beforestarting the engine after servicing. There are filters inthe reservoirs and they should be changed when thesystem is opened and the fluid is replaced. May 2012 13
£T?(3fe m? ®m?&mm The pump supplies pressure to a distribution higher fluid pressure to raise its strut, and releasesmanifold with an accumulator. The accumulator is has excess pressure to lower the vehicle. The suspensiona nitrogen charge that bears on a on a diaphragm that control solenoid acts the same way. It opens andseparates it from the hydraulic fluid. This maintains either lowers the pressure or increases it to changethe high pressure the system needs when demand the dampening characteristics of the shock. Theexceeds what the pump can supply. This pressure overall system pressure is generated by the pump andis directed to the front and rear suspension control regulated by the ABC Suction Restrictor Valve. Thevalves. Each of these has its own accumulator to help pump makes pressure and the restrictor valve bleedsmaintain pressure in its half of the system. The valves off the excess and returns it to the reservoir.house the solenoids that direct fluid into and out ofthe strut assemblies. When the vehicle is raised on a The ABC control unit knows what the systemlift, these valves are supposed to close to prevent the pressure is by means of a sensor. Its location varieslines from losing pressure. However, if you have the depending on the model you are working on. Forkey on at any time the electronics will depressurize instance, a 220 chassis has it mounted in the fluidthe system to try to lower the now fully-extended distribution manifold under the sub-frame on thesuspension. This is not a safe way to depressurize the passengers side. A 230 chassis may have it in thesystem for service as there will be some significant front control valve, which is mounted in the frontresidual psi. wheel house on the drivers side, behind the bumper. It reads the main system pressure that is being fedSTRUTTING ALONG Each strut assembly has two individual solenoids.One controls the vehicle level and the other controlsthe dampening stiffness of the strut. In the frontvalve assembly, there are two pairs of solenoids, onefor the drivers side and the other for the passengersside suspension. The same applies to the rear valve.There is an internal spring inside each strut assembly.Typically, the ABC control unit supplies power andground for the solenoids. The level solenoid both allowsVehicle 230.471Release of system pressureResult of actuation :- The actuation was okay.Status of relevant actual value:^ B 4 / 8 (Left front ABC pressure sensor): 3 Bar0 B 4 / 8 (Left front ABC pressure sensor) Voltage: 0.55 V@B4/9 (Right front ABC pressure sensor): 3 Bar^ ] B 4 / 9 (Right front ABC pressure sensor) Voltage: 0.55 Vfv]B4/10 (Left rear ABC pressure sensor): 3 Bar0B4/1O (Left rear ABC pressure sensor) Voltage: 0.55 V0 B 4 / 1 1 (Right rear ABC pressure sensor): 3 BarH B 4 / 1 1 (Right rear ABC pressure sensor) Voltage: 0.55 V[<frlB4/5 (ABC pressure sensor): 0 Bar§r]B4/5 (ABC pressure sensor) Voltage: 0.49 V Above: Using your SDS, you can command aAny time you are going to open the system, you dynamic test (aka "Rodeo Mode") where the systemmust release the pressure. Over 200 bar (3,000 psi) applies and releases pressure to all four corners ofmay be present, which can be very dangerous to the vehicle. Follow the on-screen instructions andany technician. Through your SDS, you can drop the accelerate the engine to 3,000 rpm so the pump canpressure to a safe level before you begin work. supply enough pressure for the test.14 Mercedes-Benz StarTuned
.,- i •••*#«*«_.; • 1 , pJHi ESPT I U 1 «ii ik ,1 4_ Like Chip Foose, BASF Brings A Little Extra To The Party. BASF has been doing the same with its unique color management system, led by COLOR-MAX®, the industrys most precise color matching tool. The paint-sprayed chips of COLOR-MAX ensure a perfect match the first time, every time, reducing comebacks and increasing productivity. And BASF Refinish coatings are approved by Mercedes-Benz and most major OEMs across North America. Beautiful color. Speedy matches. Its why Chip Foose sprays only BASF in his shop and has for over ten years. To learn more, visit www.basfrefinish.com or call 1-800-825-3000.1 1 1 relfc
Quality, Reliability and ValueReman k/Q Compressors are not rebuilt or refurbished, they are brought back tothe exact Mercedes-Benz approved specifications and tolerances, thus ensuringoptimal performance.Additionally, these units come preassembled with the clutch attached, so atechnician can get right to installing the entire assembly, saving time and money.By using Genuine Mercedes-Benz Remanufactured Compressors, you could save40% or more when compared to the cost of new. And like all of our remanufacturedparts, its covered by the Mercedes-Benz limited parts warranty. •"uiigat. Germany ®Genuine Remanufactured installed. Mercedes-BenzProblem solved!For more information, visit www.mbwholesaleparts.com.
GENUINE MERCEDES-BENZ REMAN A/C COMPRESSORS REMAN PART MODEL REMAN PART VEHICLE MODEL VEHICLE MODEL NUMBER YEAR NUMBER1984-1992 190D2.2 A000230121180 CL600, CL65 AMG, 2000-2006 A001230011180 S65 AMG, S600 260E, 190D2.5, 300TD, A0002302411801984-2002 2000-2009 E320, S350 A000230911180 300D,300CE, SL500 420SEL,560SEC/SEL, 2002-2007 C32 AMG A0002307811801986-1991 A000230251180 560SL 2002-2007 C230 CL 1.8 A0002309711801986-1995 190/300 series, E300D A000230111180 2002-2010 CLK-Class, C55 AMG, A001230191180 300E, 300CE, 600.S-L, SLK55 AMG1986-2002 AO00230O51180 SL600 2003-2009 CLK500 A0012301611801990-2002 500SL, SL500 A000230061180 2003-2010 SL55 AMG A0012300211801992-1993 500SEL A119230111180 E55 AMG, E320, E500, 2003-2010 A001230121180 CLS500 400SE, 400SEL, 500SEC1992-1995 A119230001180 E-Class, CLS55 AMG, S420, S5-00 A001230141180 2003-2010 CLS550 600SEL, S320, S600,1992-1999 A000230171180 300SEL 2003-2010 SL550 A001230551180 300SE, 600SEC,S600, SLK280, SLK300,1992-1999 S320, CL600 A000230221180 2005-2010 A001230541180 SLK350 CL500,300/400/500 R350, R500, ML350,1992-2004 series, S/SLK/C/CLK/ A000230701180 2006-2010 ML500, ML550, GL450, A001230871180 E-Class GL5501994-2000 C220, C280, C36 AMG A000230131180 R350, R500, ML350, 2006-2010 ML500, ML550, GL450, A002230521180 ML320, ML430, GL5501998-2005 A000230681180 ML55AMG 2009-2010 C300, C350 A0012305011801998-2010 ML500, ML350 A001230281180 2010 GLK350 A002230311180 ML350, ML500, E500,1998-2010 A000230901180 2010 : i: .0. • SL500, C/CL/S/G-Class A002230381180 "Made with the same OE components as original factory parts Assembled to original Mercedes-Benz specifications ! Results: Mercedes-Benz Quality, Reliability and Value Remanufactured for Mercedes-Benz hv Available only through your local Mercedes-Benz Dealer
the turn is compressed. The height, plunger travel, case he or she wants to raise the car when entering aand acceleration sensors for that side tell the ABC steep driveway, for example. On the 230 chassis, thereunit that. If it feels it needs to, it can apply greater is also a sport setting for stiffer damping.ABC system pressure to that sides strut assemblies,extending them, much the way a cheetah extends its Automatic functions may not work properly if theoutside legs in a 60-mph turn. Its simple physics, but ABC system is not calibrated. If you have to servicethe process is high-tech. the system, there are several functions that will need to be performed with the SDS unit. We alreadyTHE "ACTIVE" IN ABC discussed the importance of depressurizing before ABC prevents the suspension from unsettling the opening the hydraulics. Beyond that, you will have tovehicle or bottoming out if the driver goes over a perform a level calibration, plunger sensor calibration,large bump in the middle of a turn. All of the sensors and a load compensation calibration in that ordermentioned are of the three-wire type with a five-volt before the system will work as its supposed to.reference, signal wire, and ground, all connected to thecontrol unit. The body acceleration sensors have to be USING YOUR SDSable to react differently in each situation. The signal There are many dynamic tests you can performvoltage is close to 2.5 volts with the vehicle level and with the SDS to verify that the ABC components arestanding still, or while driving straight down the road functioning properly. Under "Actual Values," youat a steady speed. Under acceleration and deceleration, can monitor the signal voltages of level sensor andthe longitudinal acceleration sensor will either increase plunger travel sensor, and the individual pressureor decrease its voltage from 2.5 volts. If you turn the readings for each strut. You can also monitor thesteering wheel hard enough to the left, right and rear current draw of each plunger solenoid that controlsbody acceleration sensors will also deviate from the pressure to the strut assemblies. This will let you2.5 volt static position. You can monitor these voltages know if a solenoid is sticking, which may cause awhile someone else drives the vehicle, or you can corner to stay in the up or down position. Typically,observe these reading with your SDS. they draw under 750ma when being operated. If you see a reading higher than that, suspect a sticking Some of the functions of the ABC system can be solenoid. Level sensor signals are given in voltages,adjusted manually. To improve the center of gravity which will, of course, vary with the ride-heightat higher speeds, the ABC control unit automatically setting. You can also read the ride heights by theirlowers the vehicle, but the driver has some control of deviation from the calibrated level.the ride height via a switch on the control panel in Once you have replaced the defective hydraulic or electrical ABC component, you will have to performVehicle 230.471 some steps on a level surface before you can return the vehicle to the customer. First, you should reset|Move toward calibrated level (automatic). the system to the calibrated level. You can find thisLeft front vehicle level 3 mm under "Actuations" on your SDS. You will not noticeRight front vehicle level -6 mm the vehicle moving, but you will see the deviation inVehicle level at rear left -6 mm millimeters change. When the numbers stop changingVehicle level at rear right 3 mm the calibration is complete. Performing these last fewB4/5 (ABC pressure sensor) 190 Bar steps will improve ride control.Test prerequisite:- Engine running Knowing how the system works and how to properly service it will keep your customers coming back to you.F3: START (The actuation can be terminated Original OEM parts from your Mercedes-Benz dealerwhen the actual values stop changing.) will ensure the quality of your repairs. While you are atAfter completing an ABC repair, you should perform a the dealer picking up parts, you should also rememberlevel calibration under "Actuations" with your SDS to the filters in the ABC reservoir and the CHF lis fluidmatch the vehicle to the new components you have that Mercedes-Benz specifies for its hydraulic systems.installed. This improves ride quality and helps determine Complete the repair by recalibrating the ABC and you willif there are any other problems with the system. have serviced the vehicle just as the dealer would have. | May 2012 19
ABC Service Baselines When opening up one of these high-pressure systems there are some special procedures you must observe. th any computer-controlled electro-mechanical a requirement when replacing control units that may , there are two sides to the ABC story: the need to be programmed or initialized before bein^ il/electronic side and the mechanical side. The into service. jan be identified, monitored, and controlled For example, the code CI531-008 means that SDS (Star Diagnostic System), available for despite the fact that the right rear valve has beer from Mercedes-Benz USA. This scan tool commanded closed, the height value has changed le of reading the control unit information while the vehicle was shut off. This points to either including the software version level, which can be an external or internal leak in the right rear strut important in determining if an update needs to be assembly or valve. By clicking F3, you can access a performed to fix a problem. Of course, it can also flow chart that will take you through a step-by-step read diagnostic trouble codes (DTCs), but it goes diagnostic procedure to nail down the trouble. way beyond that by offering a guided fault-finding flowchart when you select the code you want to Before you can diagnose such a problem, however, troubleshoot. In addition, you can read specific data in the basics of the system must be in proper order. real time as the vehicle is being operated. Finally, it is There needs to be the correct amount of fluid so 1: HI llll lllllill fill! Illl With pressures reaching 200 bar (3, OOO psi), it makes sense to stick with Genuine Mercedes-Benz replacement parts.20 Mercedes-Benz StarTuned
that the ABC pump can operate at the right pressure, A filter is mounted in the reservoir, and you shouldand the pump itself needs to be capable of generating replace it whenever you open the system. This isenough pressure to raise the vehicle. an absolute must when you have had to replace the hydraulic pump. The ABC system is self-bleeding, so As mentioned in the main article, ABC uses the same you should not have to open any valves to let air outreservoir and pump as the power steering system. of the hydraulic circuits. After draining and refilling,The fluid level should be checked while the engine is however, you should let the vehicle sit for as long asrunning and the system is operational. The dipstick possible to let any air escape that may have enteredhas two levels marked on it. The higher of the two is the system while it was open. Using your SDS to putfor when the vehicle is at the lowest height setting, and the system into "Rodeo" mode will not only check thethe lower one is for when the vehicle is at the highest system for self-diagnostic codes, but will also open allheight setting. Obviously, at the lowest height setting of the valves to raise and lower the vehicle. This is anthe volume in the struts is smaller and therefore more excellent way to expel any air that may be trapped influid will return to the reservoir, and vice versa. Keep the system.this in mind when checking the level. Also, use onlyfresh new hydraulic fluid to refill after draining. Finally, Mercedes-Benz strictly specifies CHF-11S fluid for its hydraulic systems. This is a green-tinted synthetic fluid far superior to older, non-synthetics Vehicle 230.475 Control unit ABC typically used in the past for power steering. Its foolish to use anything but the right stuff. | Fault Codes Left: This kind of SDS DTC explanation makes it Code J Text | No. Status easier to zero in on a problem. Right rear suspension strut CI53I-008 moves although locking 0 STORED Below: Dont neglect that filter, and use only the recommended synthetic hydraulic fluid. May 2012 21
ClimateWith summer coming,youd better be sureyoure up-to-date onMercedes-Benz A/Cservice so you can keepyour customers in theTemperate Zone IV////=|ME3
Mercedes-Benz owners expect their creaturecomforts to work properly. Nowhere is that moreimportant than in the climate control system.Occupants require that they be kept warm in thewinter and cool in the summer. Mercedes-Benzoffers some of the most sophisticated climate controlsystems in the world, which means youll need somespecialized knowledge for diagnosis and repair.Knowing how they work is the first step. Thermotronic is a full-function automatic systemthat reads the interior and exterior temperatures andchanges compressor output, heater valve and blenddoor position. Tempmatic is another system found on2000 and later M-Class vehicles in the 163 chassisrange. This is a combination of manual and electroniccontrols that work with other control units to provideair conditioning and heater management. Thiscooperation helps reduce wiring and saves weight. Italso streamlines the diagnostic process by puttingmore information in the hands of the repair technicianthrough SDS hardware and software, available forpurchase from Mercedes-Benz.STARTING O F F SIMPLE The 163-chassis air conditioning system hasundergone some improvements over the years. Fromits introduction in 1998 to almost 2000 (11/99), thepush-button controls are only air conditioning andheater switches. They feed their inputs into a separateAAC (Automatic Air Conditioning) module mountedbehind the center control panel of the instrumentcluster. This module controls the blend door fortemperature control of the cabin. It does not have aninterior temperature sensor that provides feedbackand changes the blend door position. The push-buttoncontrol unit simply had a variable resistor that worksin conjunction with the blend door position sensor.These two switches indicate the desired temperatureto the AAC unit, which in turn positions the blenddoor. The module also has a sensor for evaporatortemperature. If the evaporator starts to freeze, thecontrol unit sends out a command to shut off the A/Ccompressor. The AAC control unit is not otherwise indirect control of the compressor. The AAM (All Activity Module) works withthe AAC module to control air conditioning andheating. It manages the coolant circulation pumpand the auxiliary cooling fans, and controls the A/Ccompressor directly. The electrical circuits for the May 2012 23
Refrigerant pressure sensor input goes to the All Activity Module, and you can measure the signal voltage atthe AAM. You should have about .75V with a full system at about 90 psi of refrigerant on both high and lowsides with the A/C system off.pump and fans are completed through relays located and resistor types that regulate blower current andin the fuse and relay box under the hood. The AAM therefore speed.has the final say on energizing the A/C compressor.It gets A/C pressure input from the high-side line In the 2002 model year (9/01 production date), therunning from the compressor to the condenser 163 chassis received a fully-automatic air conditioningby means of a three-wire sensor with a five-volt system. Interior temperature sensors were added toreference, signal wire, and ground. The AAM needs the center air and foot-well ductwork. The input from these sensors contribute to the positioning of theto see that the proper amount of refrigerant is in the blend door motor. The push-button panel is now thesystem before it will activate the compressor. If the AAC control unit and takes over direct operation ofrefrigerant level is too low, the AAM will not energize the A/C compressor and the coolant circulation pumpthe compressor so it does not seize from running dry. from the All Activity Module. The AAM is still inGETTING THE COMPRESSOR STARTED control of the auxiliary cooling fans. Rear independent You should see about .75V on the signal line with temperature control was also added. A Rear Controla fully-charged A/C system with about 90 psi on Field Control module (RCP) sends switched inputs toboth the high and low sides (system off). This should the Lower Control Field Control module (LCP), whichbe enough to get the compressor started. Then, the communicates on the C CAN with the AAC module.low side should drop to under 30 psi and the high The new all-inclusive AAC module directly managesside should increase to at least 150 psi, or higher if air distribution by controlling six motors. Three motorsthe ambient temperature is hot. Remember, if the handle the defrost vent, center vent, and foot-well ducts,evaporator core temperature sensor is indicating and the other three control the temperature blend door,freezing temperatures, the compressor will be shut fresh air/recirculation door, and rear air supply.off. If the high-side pressure becomes excessive- over 450psi - the AAM will ground the auxiliary IM VENTING!fan relay to activate both fans. This should drop the Each motor shares the same three wires from thetemperature and pressure in the high side of the AAC unit. Pin #1 is a 12V power supply, pin #3 issystem. Blower motor controls are conventional switch a ground, and pin #2 is the command signal. It is>4 lercedes-Benz StarTuned
Vehicle 230.475 Control unit KLA2Function requirementsPreconditions Specified value Actual value Result Evaporator temperature 1 - 80 °C 40.0 °C 0Coolant temperature 0- 110X 94.5 °C 0 Engine speed 400- 1400 654.0 0 Refrigerant pressure 2 - 33 bar 9.0 bar 0 Fault codes 0Function preconditions satisfiedContinue with button F2With your SDS, you can reduce your diagnostic time by evaluating the available data. Here, you can see theevaporator temperature and refrigerant pressure at a glance. You should always back up your findings withelectrical testing at the component before replacement.a time-based pulsed signal that sends individual Since the compressor is always engaged at 2%, if offersmessages out to each door motor even though they almost no resistance and does not rob horsepowerare all attached to the same wire. This means the from the engine. A compressor control valve appliessignal to control each motor is sent on the same low side pressure to move the swash plate and varywire. There is a little more to the story than that. the displacement, and, therefore, compressor output.With a paid subscription to www.startekinfo.com,you can access factory wiring diagrams. This can be FEELING THE BREEZEimportant because if you look at the 2002 model year Not all AAC systems are created equal. The bloweryou will see that an Extended Activity Module (EAM) controls on a 210 chassis are different from those ofis connected to the AAC control unit and the Lower an early 163 chassis. The 210 chassis was one of theControl Field Control module through a CAN. This is first AAC systems to use what is sometimes called aall referring to the 163 chassis; wholesale changes final stage blower motor module or blower regulator towere made to the 164. control blower speeds. The 215 and 220 chassis have a similar set up. Constant power is fed directly to the Although the AAM controls the compressor, not blower motor through the fuse panel by the firewallall compressors are the same. On the older 163 on the drivers side of the engine compartment. Thechassis, the A/C compressor has a conventional clutch ground wire of the blower motor passes through theto engage and disengage. This is how refrigerant blower regulator, which is clipped onto the blowerpressure, and therefore temperature, is maintained. motor assembly. A three-wire connector applies 12VOn later 163 chassis (2002 forward), a clutch less to the module, the command signal to vary the motorvariable-displacement compressor is used. It has a speed, and ground. The voltage supply is usually arubber coupling in place of a clutch. If the compressor larger-gauge red wire, the command signal is yellow,seizes, the fixture decouples and only the pulley and the ground is black. These wire colors do not showspins. Compressor output is controlled by positioning up on the wiring diagram since they are not on thea swash plate inside the compressor unit. The swash vehicles harness side of the connector.plate can be positioned from 2% to 100% swept volume. May 2012 25
Erc-FEis/afra Gumi The voltage command is an analog signal that comes than this, the motor may have a seizing bearing. Also,from the AAC control unit. With the blower off, the check to make sure the fan blades are not hittingvoltage is zero. As you turn the blower speed control anything. If the amperage draw is too high, you willup, the signal from the AAC unit gradually increases need to replace the blower motor before you over-taxfrom .5V to about 6V peak. If the blower module was another module.replaced in the past, it is possible that it is being over-taxed. While it forms the ground for the blower motor, DEFROST, VENT, OR FOOTWELL?it carries all of the current the motor is drawing, When dealing with a door mode control problem,which is considerable especially at high speed. Normal you must understand a few things. There is AAC anddraw is approximately 30 amps. If you measure more C-AAC. The AAC system automatically adjusts the air a I |§| <> + * 9 I •26 Mercedes-Benz StarTuned
conditioning and blend door operations to match the temperature selected. Below: With your paid subscription The C-AAC system can do the same thing, but there are temperature to Startekinfo.com you can access sensors in the ductwork that can change the position of the door to specific technical information on maintain the selected temperature. Mercedes-Benz uses a few different any system. Here is a function systems to control the position of the motors. The first is the three-wire diagram for the A/C on a 211 system mentioned earlier. A common power supply, signal command, and chassis. Notice that component ground are connected to every motor. The signal wire carries the square B14 ambient temperature sensor wave that commands the position of each motor. This can be found on the goes into the front SAM. This 163, 203, 211, and 230 chassis. The 215 and 220 chassis uses a slightly reading is used to calculate when more sophisticated system. the compressor is turned on.JU747 iJUB9 " j H22 /7s1 B10/4 |WW Q$ A32 ! , I ! N22/782 B10/6! M12/6 «! M12 .i . II i N34/1 i A32 N22/7 m«./ r • M2/9 M2/10 M2/11 «PP£ 83.40-U-2101DB M2/12 M2/13 J 21 23 I 05/05 1 [06/05 MIS/30 1 : i ii i M16/31 I J8*2 I ! B12/2 ii B12 IU742 i I II I L.R?2/3J B14 ^ MO/1 B32/2 S17/3 S17/4- S17/5 rarre 54.2LU-2109DA S17/6 tSTPE 54.21-U-2109DC rarp£ 54.21-U-2109DH FG 83U0-U-2C6Q-S9DA B32/2 C-AAC sun sensor (4 in total) Model 211 PE83.40-U-2050DA Function diagram, electrics, interior climate control May 2012 27
11 l5KMl?l=l?>ATiia [^JiffflAiiia.... - — ... The flagship sedan and coupeuse a C-AAC to manage the overallclimate control system. A separatecontrol unit handles the steppermotors directly by providing anindividual power supply to eachmotor. Just like a normal steppermotor that might be used tocontrol idle speed, EGR flow, etc.,Right: On the E-Class, the blowermotor regulator has a three-pinconnector as well as the singlespade connector for the blowermotor ground. Here, the red wireis the power supply, the yellowwire is the command signal, andthe black wire is ground. Look forup to 6V from the AAC unit on thecommand line at full blower speed.A "good" blower motor will draw approximately 30 amps when supplied battery voltage and direct ground. You shouldcheck the amp draw if you need to replace the blower regulator to verify that you will not have a repeat failure.28 Mercedes-Benz StarTuned
THE SDS TO THE RESCUE Vehicle 230.475 Control unit KLA2 After evacuating the system and then recharging it with the correct Control unit adaptations amount of refrigerant (see the Read coding and change if necessary. label in the engine compartment), the compressor may still not come Check of adjustment range of positioning motors on. If a diagnostic trouble code Teaching-in of rotary potentimoeter for center nozzle and side outlets blocks A/C operation, you will have to clear the code before theUsing your SDS you can select "Control Unit Adaptations." From here you compressor will be commanded on.can select "Normalizing Of Position Motors." This will start the process of This should be done after the A/Cmoving the motors through their full range of travel and recording their system is serviced. After servicingposition for future adjustments. a mode door control motor, you willfour wires are pulsed to ground in the AAC unit directly. This will also have to normalize the doorto change position. The stepper give you data and control from positions. There is a procedure inmotor control unit receives its other control units that work with the SDS for this. When you performdirections from the C-AAC control the AAC. This data can be critical this function the AAC control unitunit. The signals are sent over the to A/C operation. For instance, or the stepper motor control unitdedicated AAC CAN, also known as the outside temperature sensor commands each motor to the endthe KLA CAN. Other sophisticated signal is usually sent to the front or stops and remembers the positionscomponents communicate over drivers side SAM. This information of each. The automatic temperaturethis CAN, such as the center vent is used by the AAC unit to control and mode door motors can makecontrol unit, sun load sensor, and A/C operation. adjustments to meet the changingthe multi-function sensor. The conditions. Automatic functionsmulti-function sensor reads various If the sensor signal indicates a may work incorrectly if this step isdata from the environment. Aside very low temperature from a broken not followed.from reading outside temperature, or missing sensor, the circuit wouldit can read humidity, CO, and NOx. be open. Like any typical NTC There are other opportunities (Negative Temperature Coefficient) for service on Mercedes-Benz A/CThis provides information for sensor, the higher the resistance systems. Statically-charged particlean optional air filtration system. through the sensor the higher the filters are installed on most modelsOutside air can be directed through signal voltage. An open circuit would and charcoal activated filters aretwo activated charcoal filters that indicate freezing temperatures. In available for high-end models.can catch pollutants. this case, the A/C compressor would Your Mercedes-Benz dealersTOOLS IN THE ARSENAL not be commanded on since the parts department can supply you No matter which system you are electronics believe the outside air with OEM quality filters, whichworking on, you are going to need is cold. The same situation could be are better than aftermarketan SDS to finish the job. Each AAC said for the evaporator temperature replacements. Mercedes-Benz has acontrol unit has multiple sensor sensor or interior temperature detailed catalog of remanufacturedinputs and communicates with sensor. If both sensor inputs indicate A/C components such as A/Cother control units to operate the its too cold, the compressor will not compressors, so your customersA/C system. You can access all come on. Both of these inputs come can have OEM quality replacementof the data for each of these units directly into the AAC control unit. parts. Diagnosing the problemwith your SDS, which is available Only the outside air temperature accurately and installing qualityfor purchase from Mercedes-Benz sensor is sent to the SAM, so you parts is why your customers comeUSA. You can find this information may not see the data in the AAC to you for their service work. Leton www.startekinfo.com/Star control unit unless you look at Mercedes-Benz stand behind yourDiagnosis/Aftermarket. With the the overall A/C system with your work with warrantied componentsnew Xentry software, you can Xentry software. Other functions and your customers should have noeither go directly into the AAC are required to bring an A/C system problem keeping their cool. |control unit or evaluate the data online after service. May 2012 29
ARE YOU READY FORCARBON FIBER REPAIR?Carbon fiber parts will be in certain 2012Mercedes-Benz production series vehicles