On Board Diagnostic (OBD), Electrical Testing
Required special tools and equipment
- VAG1526A multimeter (Fluke 83 or equivalent)
- VW1594A connector test kit
Additional required information
Test conditions
- Vehicle voltage supply OK
- Fuses for appropriate component to be tested must be OK and checked according to wiring diagram
- Brake light OK
- Oil level of haldex clutch OK
Overview of test steps
Component to be tested
Voltage supply to control module -J492- - Perform test step 1
Function of Brake Light Switch -F- - Perform test step 2
Function of Parking Brake Warning Light Switch -F9- - Perform test step 3
Testing of Data bus wires - Perform test step 4
Function of Haldex Clutch Pump -V181- - Perform test step 5
- Switch ignition off for test steps 1 to 3.
- Raise vehicle.
- Disconnect harness connector from rear final drive.
NOTE: Use multimeter VAG1526 A and adapter cables from VW1594A connector test kit.
Connector terminal assignment
1 - Voltage supply via fuse
2 - Ground (terminal 31)
3 - B+ connection terminal 54 (brake light, brake light switch)
4 - Parking Brake Warning Light Switch F9 -
5 - K - wire from diagnostic
6 - Not occupied
7 - Data-bus connection with engine control module and ABS control module (CAN-Low)
8 - Data-bus connection with engine control module and ABS control module (CAN-High)
Test step 1
Voltage supply from control module -J492- will be checked.
- Set multimeter to measuring range 20 V.
- Switch ignition on.
- Measure at disconnected connector between terminal 1 and terminal 2 (Ground).
- Specified value: battery voltage
If specified value is not attained: repair wiring according to wiring diagram
- Switch ignition off.
Test step 2
Functioning of the Brake Light Switch -F- will be checked
- Select 20 V measuring range.
- Switch ignition on.
- Measure at disconnected connector between terminal 3 and terminal 2 (Ground).
- Specified value: smaller than 0.5 V
- Operate brake pedal.
- Specified value: battery voltage
If specified values are not attained, repair wiring according to wiring diagram.
If specified values are still not being attained, repair and adjust Brake Light Switch -F-
Test step 3
Functioning of the Parking Brake Warning Light Switch -F9- will be checked.
- Select 20 V measuring range.
- Switch ignition on.
- Measure at disconnected connector between terminal 4 and terminal 2 (Ground).
- Specified value: greater than 6 V
- Operate parking brake.
- Specified value: smaller than 0.5 V
If specified values are not attained, check wiring to instrument cluster (T32a/3) for open circuit or short circuit to B+.
- If specified values are still not being attained, check wire from terminal T32/1 (instrument cluster) via fuse to terminal 15.
- If no malfunction was detected, Parking Brake Warning Light Switch - F9 must be replaced.
NOTE: For test steps 4 and 5, use VAS5051 vehicle diagnostic, testing and information system or VAG1551 Scan Tool (ST).
VAG 1551/VAS 5051 Connecting and Selecting Functions
- VAG1551 Scan Tool (ST)
- VAG1551/3 cable
WARNING!
Observe safety measures. Refer "Safety Measures" Technician Safety Information
NOTE:
- The directions for carrying out On Board Diagnostic (OBD) in the following are only described for using VAS1551.
- Tester instructions must be followed when using vehicle diagnostic, measuring and information system VAS5051.
- Connect VAG1551 with cable VAG1551/3 A to Datalink Connector (DLC) with ignition switched off.
Test step 4
Function of the Data bus wires will be checked.
- Connect VAG1551 Scan Tool (ST) and Select "Brake Electronics" address word 03 with ignition switched on.
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and select display group number 125.
Read Measuring Value Block 125->
->1 ->2
Display fields (arrows) will follow in measuring value block. Legend of values in individual display fields can be verified in the following test table.
Indicated on display: (vehicle at stand still)
Read Measuring Value Block 125->
Engine 1 AWD 1
Test step 5
Function of the Haldex Clutch Pump -V181- will be checked.
NOTE: Vehicle must be raised, so that the wheels can rotate freely.
- Start engine.
- Engage parking brake.
- Operate clutch pedal and engage 1st gear.
- Slowly start driving (starting of the rear wheels against the parking brake must be noticeable).
Haldex Clutch Pump -V181- must continue to be lightly audible.
NOTE: Haldex Clutch Pump -V181- is located underneath control module -J492-.
If no starting of the rear wheels against the parking brake can be noticed:
- Check 2-pin harness connector at Haldex Clutch Pump -V181- and wiring according to wiring diagram
- If no malfunction could be detected, Oil Pressure Actuator -V184- is faulty.
NOTE: Oil Pressure Actuator -V184- is integrated in the control module for All-Wheel Drive.
- Operate clutch pedal and connect VAG1551 scan tool (ST) with engine running.
- Select address word 03 for "Brake Electronics".
1J0 907 379 LABS/EDL 20 IE CAN 0001
Coding 03604 WSCXXXXX
Control module identification is displayed on display of VAG1551 scan tool.
- After control module has responded, slowly start driving vehicle with parking brake operated again.
Only the front wheels should turn
If starting of the rear wheels against the parking brake can still not be noticed, the control module for All-Wheel Drive is faulty.