This document provides an overview of oscilloscopes and scan tools, which are two main types of tools used for vehicle electronic system diagnosis. It describes how oscilloscopes are used to measure voltage signals over time and the importance of adjusting settings like time base, voltage per division, and triggers. It also explains how scan tools interface with a vehicle's OBD port to retrieve diagnostic trouble codes and sensor/actuator data. Videos and web resources are provided to demonstrate the proper use of these diagnostic tools.

1. Oscilloscope and Scan Tool Use
for Vehicle Electronic Systems
APTE7504 – Vehicle Electronic Diagnosis
Week 3
Praneel Chand

2. Introduction
• Diagnostic techniques are linked to the use of test equipment
• Learning how to use tools is a practical skill
• However, you can follow some guidelines to use tools correctly and
for their intended purpose
• This lecture will discuss the two main types of tools used for vehicle
electronic system diagnosis
• Oscilloscopes
• Scan Tools

3. Oscilloscopes[1] - Introduction
• Traditionally two types: analogue or digital
• Digital scope is now universal
• An oscilloscope draws a graph of voltage
(vertical scale or Y axis) against time
(horizontal scale or X axis)
• The trace moves across the screen (left to
right) and the ‘flies back’ to start again
• The frequency at which the trace moves
across the screen is known as the time
base – can be adjusted automatically or
manually
Automotive Oscilloscope Kit (Source: www.picoauto.com)
Oscilloscope Graph
(Source:
www.picotech.com)
Trace = waveform = pattern

4. Oscilloscopes[1] - Introduction
• The signal being tested can be amplified or attenuated (reduced) like
changing the scale on a voltmeter
• The trigger, which starts the trace moving across the screen can be
caused internally or externally.
• The voltage signal under test is A/D converted and the time base is a
simple timer or counter circuit.
• Because the signal is plotted digitally on a screen from data in
memory, the picture can be saved, frozen or printed
• The Pico Automotive Diagnostics kit turns a computer into a powerful
automotive diagnostic tool for electronic diagnosis

5. Oscilloscopes[1] - Introduction
• The scope can be used to measure and test virtually all of the
electrical and electronic components and circuits in any modern
vehicle
• Excellent software is included – the user can simply select the sensor
or circuit to be tested and the software will automatically load the
required settings
• However, in diagnostics it is also important to be able to manually
adjust the oscilloscope settings in case the readings are out of range
• So we will look at how to adjust the time base, voltage amplification,
and trigger manually.

6. Oscilloscopes- Time Base [2]
• Most scopes use 10 divisions from left to right on the display
• Setting the time base means setting how much time will be displayed
in each division
• The time base should be set to allow two to four events to be
displayed
• Milliseconds is commonly used in scopes when adjusting time base
• Hence, sample time is milliseconds per division (ms/div)
• Increasing the time base reduces the number of samples per second
• Total time displayed on screen is the product of number of divisions
(usually 10) and the sample time (ms/div)

7. Oscilloscopes- Time Base [2]
• Time per division settings can vary greatly in automotive use e.g.
• Network (CAN) communications network: 2 ms/div (20 ms total)
• Throttle position (TP) sensor: 100 ms/div (1 sec total)
• Voltage measurements: 5 ms/div (50 ms total)
• The total time displayed on the screen allows comparisons to see if
the waveform is consistent or is changing

8. Oscilloscopes- Volts per Division [2]
• Volts per division (V/div) should be set to that the entire anticipated
waveform can be viewed e.g.
• Throttle position (TP) sensor: 1 V/div (10 V total)
• Battery, starting and charging: 2V/div (20 V total)
• Notice that total voltage to be displayed exceeds the components
voltage range. This allows for unexpected voltage readings

9. Oscilloscopes- DC and AC Coupling [2]
• DC coupling is the most used position on a scope because it allows the
scope to display both AC voltage and DC voltage signals present in the
circuit
• AC part of the signal rides on top of the DC component
• In AC coupling mode a capacitor is placed into the meter lead circuit to
block all DC voltage signals but allows the AC portions to pass and be
displayed
• AC coupling can be used to show output signal waveforms from sensors
such as:
• Magnetic wheel speed sensors
• The AC ripple from an alternator
• Magnetic crankshaft position sensors

10. Oscilloscopes- DC and AC Coupling [2]
• Check the instructions from the scope manufacturer for the
recommended settings to use. Sometimes its necessary to switch
between AC and DC coupling to properly see some waveforms.

11. Oscilloscopes- Triggers[2]
• External Trigger
• The waveform starts when a signal is received from another external source
rather than from the signal pickup lead
• E.g. external trigger comes from the probe clamp around the cylinder #1
spark plug wire to trigger the start on an ignition pattern
• Trigger Level
• Is the voltage that must be detected by the scope before the pattern will be
displayed
• A scope will only start displaying a voltage signal when it is triggered or is told
to start.

12. Oscilloscopes- Triggers[2]
• Trigger Slope
• Is the voltage direction that a waveform must have in
order to start the display.
• Most often, the trigger to start a waveform display is
taken from the signal itself.
• In a positive trigger, the trigger occurs at a rising (positive)
edge of the waveform.
• In a negative trigger, the trigger occurs at a falling
(negative) edge of the waveform.
• Sometimes you need to change between negative and
positive trigger if a waveform is not shown correctly.
Positive Trigger
Negative Trigger

13. Oscilloscopes- Videos & Web Resources from
Pico Automotive (available on Moodle)
• PicScope basics video
• Part 1 looks at time base and voltage division adjustment,
using multiple channels, current measurement with
inductive probe, trigger use
• Part 2 looks at buffers (time base, sampling, and
waveform)

14. Oscilloscopes- Videos & Web Resources from
Pico Automotive (available on Moodle)
• PicScope Scope School Readings
• Part 1 - Introduction to PicoScope
• Taking a measurement - covers the following key elements: Probe, Voltage, Time, and
Trigger
• Part 2 - The next step
• Looks at Rulers, Zooming, Custom settings, Saving & sharing
• Part 3 - Tips and tricks
• Looks at Coupling, Buffers, Reference waveforms, and individual channel scaling
• PicoScope 6 Automotive: Introductory training notes
• Gives a basic overview and introduction to PicoScope 6 Automotive, including both the
software itself and the hardware (PicoScope unit)

15. Oscilloscopes- Videos & Web Resources from
Pico Automotive (available on Moodle)
• PicScope Automotive Guided Tests
• Over 150 guided tests and includes example waveforms and scope settings
• Charging & starting
• Sensors
• Actuators
• Communication networks – CAN, LIN, FlexRay

16. Scan Tools – Introduction (On-board
Diagnostics OBD) [1]
• Scan tools are used for on-board diagnostics (OBD)
• OBD systems give the vehicle owner or technician access to information for
various vehicle systems
• Diagnostic information from OBD has grown considerably over the years since
its introduction in the early 80s
• Early versions of OBD would simply illuminate a malfunction indicator light
(MIL) if there was a problem but did not provide any info about the problem
• Modern OBD systems (OBD-II) uses a standardised digital communications
port to provide real-time data in addition to standardised diagnostic trouble
codes (DTCs)

17. Scan Tools –Serial Communication Port [1]
• ECUs contain self-diagnosis circuits in modern cars
• The diagnostic information produced is read via a serial link using a
scanner
• A special interface (OBD-II interface) following a standard protocol (5
types) is required to read the data. This allows many vehicle electronic
systems to connect to a central diagnostic plug.
• The sequence of event to extract DTCs from the ECU is as follows:
1. Test unit (scanner) transmits a code word
2. ECU responds by transmitting a baud rate recognition word

18. Scan Tools –Serial Communication Port [1]
3. Test unit adopts the appropriate setting
4. ECU transmits fault codes
• The test unit (scanner) converts the DTCs to suitable output text
• Further functions are possible and may include:
• Identification of ECU and system to ensure appropriate test data
• Read out of current live values from sensors. Improper values can be recognised
• System function stimulation – testing actuators and watching for response
• Programming system changes – e.g. changes in basic timing

19. Scan Tools –OBD-II Signal Protocols [1]
• 5 different signalling protocols are permitted with OBD-II
• Most cars implement only one of them
• It is often possible to deduce the protocol based on which
pins are present on the connector (J1962)
• SAE J1850 PWM (Ford)
• Pin 2: Bus +
• Pin 10: Bus –
• High voltage is +5V
• 12 byte message length
OBD-II Port 16
pin connector
(J1962) [1]
4 – battery
ground/earth
7 – K-line
15 – L-linr
16 – battery
positive

20. Scan Tools –OBD-II Signal Protocols [1]
• SAE J1850 VPW (General Motors)
• Pin 2: Bus+
• Bus idles low
• High voltage +7V
• Decision point is +3.5V
• 12 byte message length
• ISO 9141-2: (Chrysler, European, Asian vehicles)
• Pin 7: K-line
• Pin 15: L-line (optional)
• UART signalling
• K-line idles high
• 12 byte message length

21. Scan Tools –OBD-II Signal Protocols [1]
• ISO 14230 KWP2000 (Keyword Protocol 2000)
• Pin 7: K-line
• Pin 15: L-line (optional)
• Physical layer identical to ISO 9141-2
• 255 bytes message data field
• ISO 15765 CAN (made by Bosch for automotive & industrial control)
• Since 2008 all vehicles sold in US (and most other places) are required to implement
CAN as one of their signalling protocols
• Pin 6: CAN high
• Pin 14: CAN low
• All OBD-II pin-outs use the same connector but different pins
• Exceptions are pin 4 (battery ground) and pin 16 (battery positive)

22. Scan Tools –OBD-II Signal Protocols [3]
• ISO 15765 CAN (made by Bosch for automotive
& industrial control)
• Since 2008 all vehicles sold in US (and most other places) are
required to implement CAN as one of their signalling
protocols
• Since most modern cars have ECUs with a CAN interface for
exchanging data between electronic systems, this option for
communication with the tester (scan tool) has become
dominant
Diagnosis connector with pin
outs for various standards [3]

23. Scan Tools –Videos (can be accessed via
Moodle)
• Open the page Scan Tools Videos under “In class” in Week 3 section
1. How to use an OBD-II Scan Tool
2. Petroject: Hanatech Scan Tool Demo
• Demonstration on using the Hanatech Ultrascan P1 which is similar to the
Multiscan P1 (which the department has) but with added features of
graphing capability and 4 channel oscilloscope.

24. Scan Tools –Web Resources (can be accessed
via Moodle)
• Open the page Scan Tools Web Pages under “In class” in Week 3 section
1. Scan Tool Help
• Basic introduction to scan tools and types: Code readers, scan tools, DIY scan
tool product information, Professional level scan tools, scanner software
(software that transforms your desktop or laptop PC, tablet, smart phone etc
into a code reader or scan tool)
2. How to Read Diagnostic Trouble Codes (DTCs)
• Contains information on how to read DTCs using a scan tool. An eight step
process outlined for reading fault codes and clearing them. The diagnostic fault
codes is an alphanumeric code which you need to find the definition of. You
need to search the internet or get the info from the car manufacturer.
Fortunately, there are some online databases for getting fault code definitions
(see 4. Actron Diagnostic Code Lookup and 5. Bosch Diagnostics below as
examples)

25. Scan Tools –Web Resources (can be accessed
via Moodle)
• Open the page Scan Tools Web Pages under “In class” in Week 3 section
3. OBD-II CAN Diagnostic Codes
• Full list of CAN network communication diagnostic codes for the various
communication buses control module communications.)
4. Actron Diagnostic Code Lookup
• Online DTC code look up
5. Bosch Diagnostics
• Includes resources on DTC code look up and vehicle coverage charts

26. Student Activity Time
• Use the Picoscope oscilloscope to measure the CAN bus, actuator,
and sensor signals on the demonstration model
• Use the Hanatech Multiscan P1 to retrieve diagnostic codes from the
workshop car.
www.flickr.com

27. Electronic System Diagnosis and Repair
• You will learn how to diagnose various vehicle electronic systems later
on in the semester (weeks 9-13)
• You will learn about the scope and of the rectification (repair) process
in the last weeks of the semester

28. References
• [1] T. Denton, Advanced Automotive Fault Diagnosis: automotive
technology: vehicle maintenance and repair. NY: Routledge, 2012.
• [2] J. D. Halderman, Diagnosis and Troubleshooting of Automotive
Electrical, Electronic, and Computer Systems. NJ: Pearson, 2012.
• [3] R. Bosch, Bosch Automotive Electrics and Automotive Electronics
Systems and Components, Networking and Hybrid Drive. Germany:
Robert Bosch, 2013.