P0499moderate severityPowertrain
Evaporative Emission System Vent Valve Control Circuit High
on 2005-2011 Audi A6 4.2L V8 · AWD
What this code means
The PCM detects high voltage in the EVAP vent valve control circuit. This may keep the vent valve from sealing during leak diagnostics.
Symptoms
- Check engine light on
- Failed EVAP monitor
- No noticeable driving symptoms
Common causes
- Open circuit in vent valve wiring
- Faulty vent valve solenoid
- Corroded or loose connector
- Faulty PCM driver circuit
Diagnostic steps
- Scan and record freeze frame data
- Inspect vent valve wiring for opens
- Measure vent valve circuit voltage
- Test vent valve solenoid resistance
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