Subaru Common Trouble Codes

Common Trouble Codes and Potential Fixes

Applicable Vehicle:

  • All supported Subaru vehicles

Common DTC's With Potential Fixes

  • P0011 Camshaft Position
    • Timing Over-Advanced (Bank 1) Typically caused by an incorrectly installed timing belt, clogged or failing AVCS solenoid, clogged filter in the banjo bolt for the oil feed line on the AVCS solenoid, or a stuck AVCS cam gear that is unable to actuate

  • P0012 Camshaft Position
    • Timing Over-Advanced (Bank 2) Typically caused by an incorrectly installed timing belt, clogged or failing AVCS solenoid, clogged filter in the banjo bolt for the oil feed line on the AVCS solenoid, or a stuck AVCS cam gear that is unable to actuate.

  • P0030 Front O2 Sensor Heater Control Circuit
    • Typically caused by a failing or failed front O2 sensor, a blown fuse for the O2 heater control circuit, a poor electrical contact on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0031 Front O2 Sensor Heater Control Circuit Low
    • Typically caused by a failing or failed front O2 sensor, a blown fuse for the O2 heater control circuit, a poor electrical contact on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0032 Front O2 Sensor Heater Control Circuit High
    • Typically caused by a failing or failed front O2 sensor, a blown fuse for the O2 heater control circuit, a poor electrical contact on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0037 Rear O2 Sensor Heater Control Circuit Low
    • Typically caused by a failing or failed rear O2 sensor, a blown fuse for the O2 heater control circuit, a poor electrical contact on the rear O2 sensor, or damaged wiring between the rear O2 sensor and ECU.

  • P0038 Rear O2 Sensor Heater Control Circuit High
    • Typically caused by a failing or failed rear O2 sensor, a blown fuse for the O2 heater control circuit, a poor electrical contact on the rear O2 sensor, or damaged wiring between the rear O2 sensor and ECU.

  • P0131 Front O2 Sensor Low Voltage
    • Typically caused by a failing or failed front O2 sensor, a poor electrical connection on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0132 Front O2 Sensor High Voltage
    • Typically caused by a failing or failed front O2 sensor, a poor electrical connection on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0133 Front O2 Sensor Circuit Slow Response
    • Typically caused by a failing or failed front O2 sensor, a poor electrical connection on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0134 Front O2 Sensor Circuit No Activity Detected
    • Typically caused by a failing or failed front O2 sensor, a poor electrical connection on the front O2 sensor, or damaged wiring between the front O2 sensor and ECU.

  • P0137 Rear O2 Sensor Circuit Low Voltage 
    • Typically caused by a failing or failed rear O2 sensor, a poor electrical connection on the rear O2 sensor, or damaged wiring between the rear O2 sensor and ECU.

  • P0138 Rear O2 Sensor Circuit High Voltage
    • Typically caused by a failing or failed rear O2 sensor, a poor electrical connection on the rear O2 sensor, or damaged wiring between the rear O2 sensor and ECU.

  • P0139 Rear O2 Sensor Circuit Slow Response
    • Typically caused by a failing or failed rear O2 sensor, a poor electrical connection on the rear O2 sensor, damaged wiring between the rear O2 sensor and ECU, or the rear O2 sensor being spaced out of the direct exhaust stream.

  • P0171 System too Lean
    • Typically caused by an intake/intercooler air leak, incorrectly calibrated aftermarket intake system, dirty or failing mass air flow sensor, failing front O2 sensor, or fuel delivery issue.

  • P0172 System too Rich
    • Typically caused by an intake/intercooler air leak, incorrectly calibrated aftermarket intake system, dirty or failing mass air flow sensor, failing front O2 sensor, or fuel delivery issue.

  • P0244 Turbo Wastegate Solenoid “A” Range/Performance
    • Boost pressure has exceeded the maximum set threshold. Run LWG (Low Wastegate) map if available. Can also be caused by failing or misconfigured boost control system, dramatic drop in ambient temperatures, and accelerating aggressively in a high gear at a low RPM.

  • P0301 Cylinder 1 misfire detected
    • Typically caused by a failing spark plug, failing coil pack, failing fuel injector, intake/intercooler air leak, aftermarket lightweight flywheel, aftermarket lightweight crank pulley, or insufficient compression.

  • P0302 Cylinder 2 misfire detected
    • Typically caused by a failing spark plug, failing coil pack, failing fuel injector, intake/intercooler air leak, aftermarket lightweight flywheel, aftermarket lightweight crank pulley, or insufficient compression.

  • P0303 Cylinder 3 misfire detected
    • Typically caused by a failing spark plug, failing coil pack, failing fuel injector, intake/intercooler air leak, aftermarket lightweight flywheel, aftermarket lightweight crank pulley, or insufficient compression.

  • P0304 Cylinder 4 misfire detected
    • Typically caused by a failing spark plug, failing coil pack, failing fuel injector, intake/intercooler air leak, aftermarket lightweight flywheel, aftermarket lightweight crank pulley, or insufficient compression.

  • P0420 Catalyst System Efficiency Below Threshould
    • Typically caused by a higher flowing aftermarket downpipe without a catalyst or with a catalyst that doesn't meet the efficiency and cleanliness requirements of the ECU

  • P0451 Evaporative Emission Control System Pressure Sensor Range/Performance Problem
    • Typically  is based on a variance between the MAP reading and baro air pump reading. Reset the ECU, then (without starting car and engine OFF) log "Man. Abs. Pressure" and "Baro Pressure" with the key on. They should be pretty close to one another normally but when the problem
      is occurring (P0451), you'll be able to tell which is the culprit (with engine off, each sensor should be reading baro pressure - usually they will be within a few tenths (psi) of one another).


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