Speed Signal, Checking
The following procedure requires a test drive. Observe all safety precautions.
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
Test requirements
- The Speedometer -G21- OK.
- The Motronic Engine Control Module (ECM) -J220- 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:
| Diagnostic text | Specified value | |||
|---|---|---|---|---|
| Vehicle Speed | Approx. 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 Motronic Engine Control Module (ECM) -J220- 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 repair work, the following work steps must be performed in the following sequence:
- Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .
-- End of diagnosis.