P0177
Fuel Composition Sensor Circuit Range/Performance
- Severity
- Medium
- Driving
- Drivable — book it in
The fuel composition sensor is producing a signal within its valid range that does not agree with what the module expects - for instance a reading that never changes across a complete tank of different fuel, or one that swings more than the fuel in the tank possibly could.
Possible causes
- CommonFailed fuel composition sensor
- CommonCorroded or wet connector at the sensor
- CommonWiring fault between the sensor and the module
- PossibleWater or contamination in the fuel confusing the measurement
- PossibleSensor coated with deposits after long service
What you might notice
- Rough running or hesitation, worst after a fuel change
- Hard starting in cold weather
- Loss of power
- Poor fuel economy
- Check engine light on
What to check, in order
- Read the ethanol percentage on live data. A reading stuck at one value through a full tank change, or one that jumps around while driving, both condemn the sensor.
- Inspect the connector for corrosion and water. This sensor lives in the fuel line, often under the vehicle, and its connector suffers accordingly.
- Check the wiring for chafing along its run. Underbody harnesses take a beating from road debris and salt.
- Rule out contaminated fuel before replacing the sensor. Water reads as a composition fault and is much cheaper to find than to overlook.
- Track the reading across a full tank rather than judging it on one look. This code is about how the value behaves over time, so a single snapshot cannot confirm or clear it.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Fuel and air metering
P0100P0101P0102P0103P0104P0105P0106P0107P0108P0109P0110P0111P0112P0113P0114P0115P0116P0117P0118P0119P0120P0121P0122P0123P0124P0125P0126P0127P0128P0129P0130P0131P0132P0133P0134P0135P0136P0137P0138P0139P0140P0141P0142P0143P0144P0145P0146P0147P0148P0149P0150P0151P0152P0153P0154P0155P0156P0157P0158P0159P0160P0161P0162P0163P0164P0165P0166P0167P0168P0169P0170P0171P0172P0173P0174P0175P0176P0177P0178P0179P0180P0181P0182P0183P0184P0185P0186P0187P0188P0189P0190P0191P0192P0193P0194P0195P0196P0197P0198P0199