P1137moderate severityPowertrain
Front Oxygen A/F Sensor Range/Performance Problem
on 2002 Subaru Impreza 2.5L H4 · AWD
What this code means
The PCM has detected that the front air-fuel ratio sensor is not performing within the expected range. The sensor output does not correctly correspond to the actual air-fuel ratio, affecting closed-loop fuel control accuracy.
Symptoms
- Check Engine Light
- Poor fuel economy
- Rough idle
- Hesitation on acceleration
- Failed emissions test
Common causes
- Contaminated A/F sensor from oil or coolant
- Aging A/F sensor with degraded performance
- Exhaust leak near sensor
- Fuel quality issue affecting sensor
- Incorrect sensor installed
Diagnostic steps
- Monitor A/F sensor output on scan tool during various conditions
- Check A/F sensor heater operation
- Inspect for exhaust leaks near sensor
- Check for oil or coolant contamination in exhaust
- Compare sensor readings to known good values
Repair notes
Replace the front A/F sensor if its output does not match the expected range during testing.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1