Operation CHARM: Car repair manuals for everyone.

Speed Signal, Checking






Speed Signal, Checking

The following procedure requires a test drive. Observe all safety precautions.

Special tools, testers and auxiliary items required

Multimeter.

Wiring diagram.

Test requirements

The Speedometer (G21) OK.

The Engine Control Module (ECM) (J623) fuses OK.

Battery voltage at least 12.5 volts.

All electrical consumers such as, lights and rear window defroster, switched off.

A/C switched off.

Ground (GND) connections between engine/transmission/chassis OK.

Ignition switched off.

Function test

- Connect the scan tool.

- Perform a road test with a vehicle speed greater than 5 Km/h.

- Using the scan tool, Check the vehicle speed:





- Compare the vehicle speed on the scan tool to the Speedometer (G21).

Specified value: a difference of no greater than 10%.

If the specified value was not obtained or no speed was displayed:

- Check the wiring from the Engine Control Module (ECM) (J623) to the Instrument Cluster Control Module (J285) for an open circuit, Short to Battery (+), or to Ground (GND).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

Final procedures

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

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

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

3. If the DTC memory was erased, generate readiness code. => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End of diagnosis.