OBD-II code · Powertrain (generic)
P0178 Fuel Composition Sensor Circuit Low Input
The flex-fuel composition sensor signal is below the minimum threshold. Likely shorted to ground, open circuit or failed sensor.
Is it safe to drive with P0178?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySignal wire shorted to ground
- PossibleSensor failed
- Less likelyConnector pins corroded - high contact resistance
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–2 h
- Emissions test
- Likely to fail
- Parts involved
- Flex Fuel Composition Sensor, Sensor Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.