P0177
Fuel Composition Sensor Circuit Range / Performance
The flex-fuel composition sensor signal is within electrical limits but does not match expected values for the current fuel mix or rate-of-change is implausible.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Sensor drifted out of calibrationCommon
- Fuel contaminated (water, dirt)Possible
Parts involved
- Flex Fuel Composition Sensor
P0177 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.