P0479moderate severityPowertrain
Exhaust Pressure Control Valve Circuit Intermittent
on 2002 Audi A6 3.0L V6 · AWD
What this code means
The exhaust pressure control valve circuit is intermittent for the second sensor/valve. The PCM sees erratic signals affecting backpressure control.
Symptoms
- Check engine light on
- Erratic engine performance
- Reduced power under load
Common causes
- Intermittent wiring fault
- Corroded connector
- Faulty exhaust pressure control valve
- Bad PCM
Diagnostic steps
- Retrieve code and freeze frame
- Inspect and wiggle-test wiring
- Check valve signal with scan tool
- Repair connection or replace valve
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