Speed Signal, Checking Audi TT 8N

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

Special tools, testers and auxiliary items required

1. Multimeter.
2. Wiring diagram.

Test requirements

1. The Speedometer G21 OK.
2. The Motronic Engine Control Module (ECM) J220 fuses OK.
3. Battery voltage at least 12.5 volts.
4. All electrical consumers such as, lights and rear window defroster, switched off.

1. A/C switched off.
2. Ground (GND) connections between engine/transmission/chassis OK.
3. Ignition switched off.

Test procedure

1. Perform a preliminary check to verify the customers complaint. Refer to --> «General Diagnosis»(ref-276276-S40851803372008010300000) .

Start diagnosis

1. Connect the scan tool.
2. Perform a road test with a vehicle speed greater than 5 Km/h.
3. Using the scan tool, Check the vehicle speed

1. 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

1. 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).
2. Check the wiring connection for damage, corrosion, loose or broken terminals.
3. If necessary, repair the faulty wiring connection.

Final procedures

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

1. Check the DTC memory.
2. If necessary, erase the DTC memory. Refer to «Diagnostic Mode 04: Reset/Delete Diagnostic Data»(ref-276276-S31279847122008010300000) .
3. If the DTC memory was erased, generate readiness code. Refer to «Readiness Code»(ref-276276-S05799074302008010300000) .

End of diagnosis.