Engine

P03F9 — B Camshaft Position Actuator Position Sensor C Circuit High, Bank 1

Severity: medium Drive with care, to a shop

What P03F9 means

P03F9 is a manufacturer-specific code. The engine control unit detected too high a voltage in the C circuit of the position sensor for the B camshaft actuator (phaser) on Bank 1. This sensor reports how far the phaser has turned so the variable valve timing (VVT) system can be controlled accurately. Exactly which circuit is C and which camshaft is B depends on the make and engine. Some sources confuse this code with a cylinder 2 misfire, but by definition it concerns the phaser position sensor.

Symptoms

  • Check engine light on
  • Rough idle
  • Reduced power and sluggish acceleration
  • Increased fuel consumption
  • Hesitation or stumbling under throttle
  • Occasionally stalling

Possible causes

  1. Faulty camshaft actuator position sensor
  2. Open, shorted or corroded wiring or connector at the sensor
  3. Signal circuit shorted to power
  4. Faulty camshaft phaser (VVT actuator)
  5. Low oil level, degraded oil or low oil pressure
  6. Faulty VVT oil control solenoid
  7. Rarely, an ECM/PCM internal fault

How to diagnose

  1. Read all codes and freeze-frame data and look for related cam timing or misfire codes.
  2. Check oil level and condition; change oil and filter if it is dirty or degraded.
  3. Inspect the sensor harness and connector for chafing, corrosion and damaged pins.
  4. Check reference voltage, signal and ground at the sensor connector, and test the signal wire for a short to power.
  5. Compare specified and actual cam angle in live data.
  6. Command the VVT solenoid with a scan tool and verify the response.
  7. If the deviation persists, check timing marks and timing chain stretch.
  8. If the wiring is good, test the sensor and phaser before suspecting the ECM.

Common fixes

  • Replace the camshaft actuator position sensor
  • Repair or replace damaged wiring and connectors
  • Replace the VVT solenoid or camshaft phaser
  • Change oil and filter and fix the cause of low oil pressure
  • Repair or replace the timing chain and related parts if timing is off

Questions and answers

What does code P03F9 mean?

It means the signal in the C circuit of the Bank 1 B camshaft actuator position sensor is too high. The ECU cannot correctly read the position of the VVT phaser.

Can I drive with P03F9?

Briefly and without heavy loads, to reach a shop. The engine may lose power and run rough, and driving for long can cause further problems.

Is P03F9 the same as a cylinder 2 misfire?

No, by definition the code points to the phaser position sensor circuit. However, incorrect cam timing can make the engine run rough in a way that feels like a misfire.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.