P0176 Fuel Composition Sensor Circuit

The fuel composition sensor is fitted only to flex-fuel vehicles that can run on petrol or ethanol up to E85. GM uses a capacitive sensor in the fuel line whose square-wave output frequency gives the ethanol content – 50 Hz for E0 up to 150 Hz for E100 – while the pulse width carries the fuel temperature. Ford has calculated the ethanol content from the oxygen sensor feedback after refuelling since model year 2000 and has no such sensor. P0176 is the general circuit fault of this sensor without telling low from high. GM's current documents use P0178/P0179 instead, so P0176 is mainly to be expected on older flex-fuel vehicles or other makes. GM issued a special coverage for 2013–2014 flex-fuel models (10 years/150,000 miles) because road salt could make the sensor fail electrically, turning on the MIL and disabling remote start. No manufacturer document using exactly this code was found; the description rests on CARB's circuit monitoring requirement and component information.

Likely causes

Symptoms

• Check engine light on
• Ethanol content in scan data implausible or frozen
• Starting problems on E85

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, static.nhtsa.gov, gsi.ext.gm.com.