Vehicle Speed Signal, Testing

Vehicle Speed Signal, Testing

NOTE:
- The road speed signal is generated by the speedometer sender -G22 (on the gearbox) and is processed in the instrument cluster.
- The processed signal goes to contact 54 on the engine control module and is used for idling speed stabilization and for the damping of load change jolts when changing gear.

Test requirement:
- Speedometer (including display) must be functioning properly.

Fault-finding:
See Electrical Wiring Diagrams, Troubleshooting & Component Locations

Test sequence

WARNING: To avoid accident risks when road testing the vehicle with test equipment, always observe the relevant safety precautions

- Connect the vehicle diagnostic, testing and information system VAS 5051, Vehicle Diagnostic, Testing and Information System VAS 5051, Connecting and Selecting Functions , and select the vehicle system "01 - Engine electronics" from the menu. When doing this the engine should be idling.







Display on VAS 5051:
- Select the diagnosis function "08 - Read data block" from the menu -1-







Display on VAS 5051:
1 - Enter display group
(figures up to 255)
- Using the keypad -2-, enter "005" to select Display group 005 and confirm entry with Q button.







Display on VAS 5051:
- Take vehicle for a test drive and check whether the road speed appears in display zone -3-.
- If the road speed does not appear, raise the vehicle (preferably using a lifting platform) until the front left wheel is clear of the ground.
- Connect test box VAG 1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself. Scan Tool Testing and Procedures
- Connect VAG 1527 B voltage tester to sockets 3 (positive) and 54 (road speed signal) on test box VAG 1598/31.
- Switch on the ignition and turn the front left wheel by hand.
- The LED should flash very briefly.

If the LED does not flash:
- Test for open circuit and short to positive or Ground in the following wiring connection:

Test box VAG 1598/31 Instrument cluster
Socket Contact
54 See Electrical Wiring Diagrams, Troubleshooting & Component Locations

- Correct short circuit or open circuit if necessary.