P0179moderate severityPowertrain
Fuel Composition Sensor Circuit High
on 2002 Audi A6 3.0L V6 · AWD
What this code means
The PCM detects a high voltage signal from the fuel composition (flex fuel) sensor circuit. The sensor reading is out of range on the high side.
Symptoms
- Check engine light on
- Poor performance on flex fuel
- Reduced fuel economy
Common causes
- Faulty flex fuel sensor
- Short to voltage in wiring
- Open circuit
- Faulty PCM
Diagnostic steps
- Scan for stored codes and freeze frame
- Check flex fuel sensor signal voltage
- Inspect wiring for shorts to power or opens
- Replace fuel composition sensor if faulty
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