Vehicle Speed Signal, Checking

Vehicle Speed Signal, Checking

Test requirement:

• Function and display of speedometer OK. Troubleshooting:

CAUTION!
• Test and measuring equipment must always be secured to the rear seat and be operated from there by a second person.

If test and measuring instruments are operated from the front passenger's seat and the vehicle is involved in an accident, there is a possibility that the person sitting in this seat may receive serious injuries when the airbag is deployed.

- Connect diagnostic tester.

- Start engine and let run at idle.

- In diagnostic function "33 - OBD", select "Diagnostic mode 1 - Check measuring values".

- Select the desired measuring value "PID 13: Vehicle speed".

- Perform a road test, and have the 2nd person observe the indication on the display.





- End diagnosis and switch ignition off.

If no speed is displayed:

The speed signal is transferred from the Engine Control Module (ECM) to the instrument cluster via wire connection or via CAN-Bus, depending on version.

- Checking wire connections

- Check terminal resistance for CAN-Bus => [ CAN-Bus Terminal Resistance, Checking ] CAN-Bus Terminal Resistance, Checking.

Final procedures

After repair work, the following work steps must be performed in the mentioned sequence:

1. Check DTC memory => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase DTC memory => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If DTC memory was erased, generate readiness code => [ Readiness Code ] Readiness Code.

- End diagnosis and switch ignition off.