Speed Signal, Checking

Speed Signal, Checking

Test requirement
- Function and display of speedometer OK.

CAUTION: To reduce the risk of accident during road tests, always observe safety precautions.

- Connect the diagnostic tester.
- Start the engine and let run at idle.
- Select "Diagnostic mode 1: Obtain data".
- Select the measured value "PID 13: Vehicle speed".
- Perform a road test, and have the 2nd person observe the indication on the display.
- Check the specified value of the vehicle speed:







- End the diagnosis and switch ignition off.

If no speed is displayed:
The speed signal is transferred from the Engine Control Module (ECM) J623 to the instrument cluster via wire connection or via CAN-Bus, depending on version.
- Check the wiring connections.
- Check the terminal resistance for the CAN-Bus.

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

- End diagnosis and the switch ignition off.