VVC AUTO 85.5 - Smog Technician - Level 1 - Baseline testing


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VVC AUTO 85.5 - Smog Technician - Level 1 - Baseline testing

  1. 1.  Why baseline  Before and after repairs  Baselining with a 5 gas analyzer  Baselining with a scope, scan tool, or DVOM  Correlation of baseline reading with Bar „97 test results
  2. 2.  Diagnosing an emission failure is different from many auto repairs  Sometimes a vehicle will “run fine” but fail a smog test  It can be hard for a tech or customer to visualize a smog failure
  3. 3.  A baseline test consists of:  Monitoring all 5 gases at:  Stabilized operating temperature  Idle  3000 RPM (no load)  ASM mode 1  ASM mode 2
  4. 4.  Performing a baseline test before and after a repair will be an indication of how successful your repair was  Sometimes a repair of one gas will raise another gas out of limits  Remember you are going to compare the two sets of readings, so always perform a before and after baseline test exactly the same, or results will be inaccurate
  5. 5.  Analyze the “after repair” baseline readings and the “before repair” baseline readings by comparing the two sets of readings.  Calculate the difference in percentages  If the percentage of reduction is the same or higher (cleaner)  Your repair was probably successful  Be sure to check the other gas readings
  6. 6. Equipment used to gather baseline readings  DVOM  Hook up to 02 sensor  Positive lead to 02 sensor return wire  Negative lead to good ground  Scan tool  Hook up and program
  7. 7.  DVOM to fuel injector (if no data stream)  Positive lead to fuel injector ground  Negative lead to good ground  Set on ms scale  Warm up vehicle  Monitor the O2 ( voltage & frequency) and the Injector (pulse width) simultaneously.  O2 should fluctuate above and below .450 volts at least once every couple of seconds  A rich exhaust must = a lean command
  8. 8.  If 02 sensor reading is biased high or low you have a problem (may not be 02 sensor)  Baselining using the 02 sensor and M/C command will monitor CO only
  9. 9.  A digital storage oscilloscope (DSO) will give more accurate information  If a small misfire is present more oxygen is in the exhaust stream  The 02 sensor wave form will have a higher frequency  Using this method only CO & HC problems can be identified
  10. 10.  BAR „97 analyzer  Road test -- put on analyzer  Monitor and record all 5 gases during 4 conditions mentioned before  Other test equipment utilized during this baseline test may include timing light, DSO, Digital Pyrometer etc.
  11. 11.  Special note: If all OEM emissions equipment is not hooked up and operating as designed, baseline test results will be inaccurate. (missing, modified or disconnected emission systems must be repaired first!)