P0898moderate severityPowertrain
Transmission Control System MIL Request Circuit Low
on 2009 Audi A8 4.2L V8 · AWD
What this code means
The transmission control module is commanding the malfunction indicator lamp but the request circuit reads low voltage. This indicates a wiring or module communication fault.
Symptoms
- Check engine light behavior abnormal
- Transmission warning present
- Possible limp mode
Common causes
- Short to ground in MIL request circuit
- Faulty transmission control module
- Damaged wiring or connectors
- PCM/TCM communication fault
Diagnostic steps
- Check MIL request circuit for shorts to ground
- Inspect wiring and connectors at TCM
- Verify PCM and TCM communication
- Test module voltages and grounds
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