P0864moderate severityPowertrain
TCM Communication Circuit Range/Performance
on 2003 Audi A6 3.0L V6 · AWD
What this code means
The signal on the transmission control module communication circuit is outside the expected range or performing erratically. This indicates a data quality problem rather than a total loss of communication.
Symptoms
- Intermittent shift problems
- Transmission warning light
- Delayed gear engagement
Common causes
- Intermittent wiring fault
- Corroded connector pins
- Faulty TCM
- Signal interference on data bus
Diagnostic steps
- Retrieve all stored codes
- Inspect connectors for corrosion
- Wiggle-test harness while monitoring data
- Compare TCM signal to specification
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