P0177
Fuel Composition Sensor Circuit Range/Performance
Moderatesensor
Overview
The P0177 diagnostic trouble code means the PCM has identified a fuel composition sensor circuit range/performance problem. This code indicates that a sensor or its circuit is not providing expected readings to the engine management system. Faulty sensor data can cause the PCM to make incorrect adjustments, affecting engine performance.
Symptoms
- Hard starting in certain conditions
- Incorrect gauge readings
- Engine running rough
- Reduced engine performance
Common Causes
- Faulty sensor (out of range or failed)
- Physical damage to sensor
- Sensor contamination or buildup
- Corroded or damaged sensor connector
Diagnosis Steps
- 1Connect an OBD-II scanner and read all stored trouble codes and freeze frame data
- 2Locate the specific sensor referenced by the code
- 3Inspect the sensor connector for corrosion, damage, or loose pins
- 4Test the sensor output using a multimeter or scan tool live data
- 5Check the wiring between the sensor and the PCM for opens or shorts
Estimated Repair Cost
$75 — $350
Cost varies by vehicle, location, and repair shop. Includes parts and labor.
Commonly Affected Vehicles
Subaru ImprezaHonda CivicHyundai ElantraMazda 3
Related Codes
More Sensor Codes
P0070Ambient Air Temperature Sensor Circuit
LowP0071Ambient Air Temperature Sensor Range/Performance
LowP0072Ambient Air Temperature Sensor Circuit Low
LowP0073Ambient Air Temperature Sensor Circuit High
LowP0074Ambient Air Temperature Sensor Circuit Intermittent
LowP0095Intake Air Temperature Sensor 2 Circuit
LowFrequently Asked Questions
Most automotive sensors last 80,000-150,000 miles, though this varies by sensor type and driving conditions. Oxygen sensors and temperature sensors tend to degrade gradually over time.