P0177 - Fuel Composition Sensor Circuit Range/Performance
Some vehicles may run on a mixture of different fuels and the ECM will use a sensor to check that the mixture of the fuels is at the correct ratio
Fault Code Explained
The ECM has detected that the sensor output is incorrect due to an undefined reason. The sensor value will be within its normal operating parameters but is not reading or responding as expected for the current engine operating conditions.
It is recommended to follow the manufacturers recommended test plan when diagnosing this fault code