OBD-II FAULT CODE
P0178
Fuel Composition Sensor Circuit Low Input
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0178.
- Check Engine light
- Poor drivability or reduced fuel economy depending on fault
- Low signal voltage
- Weak power supply
- High resistance/poor ground
- Failed sensor
- Scan all modules and record freeze-frame data before clearing codes
- Check battery voltage and related fuses
- Check sensor reference voltage, ground and signal voltage
- Repair poor ground/power feed or replace confirmed faulty sensor
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Disclaimer: Information is provided for general guidance only and may not apply to all vehicles. Always consult a qualified technician.