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P0011 Code on 2018 Forester - Rough Idle & Check Engine

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Mike T. · rep 0 · May 25, 2:13 AM · 1 replies · solved · Question

Vehicle: 2018 Subaru Forester 2.5i Premium

Hey everyone, I'm having an issue with my 2018 Subaru Forester 2.5i Premium. The Check Engine Light came on a few days ago, and I've noticed a rough idle, especially when the engine is cold. It seems to smooth out a bit once it's warmed up, but the CEL stays on.

I scanned it with my OBD-II reader and got a P0011 code: 'Camshaft Position A - Timing Over-Advanced or System Performance (Bank 1)'.

What's usually involved in fixing this on a Forester? Could it be an oil issue, or something more serious like the AVCS system?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:13 AM

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The P0011 code on your 2018 Subaru Forester indicates an issue with the Variable Valve Timing (VVT) system, specifically the intake camshaft position on Bank 1 (driver's side). This system, known as Active Valve Control System (AVCS) in Subarus, uses oil pressure to adjust camshaft timing for optimal performance and efficiency.

Common Causes:

  • Low or Contaminated Engine Oil: This is a very common cause. The AVCS system relies heavily on clean, properly pressurized oil. Dirty oil can clog the oil control valves (OCVs).
  • Faulty Oil Control Valve (OCV)/AVCS Solenoid: These valves control the oil flow to the cam phasers. If an OCV is stuck, clogged, or electrically faulty, it can cause incorrect cam timing.
  • Faulty Camshaft Position Sensor: While less common for P0011 specifically, a faulty sensor could send incorrect readings.
  • Timing Chain/Belt Issues: In rare cases, stretched timing chains or incorrect timing belt installation (if applicable) could contribute, but usually, other codes would accompany this.

Diagnostic Steps:

  1. Check Engine Oil Level and Condition: Ensure your oil is at the correct level and isn't excessively dirty or old. An immediate oil and filter change with the correct viscosity oil is a good first step, especially if it's due.
  2. Inspect and Test OCVs: The OCVs for the AVCS system can be removed, inspected for clogs, and tested for proper operation (resistance check and applying 12V to see if they click/move). There's one for each intake and exhaust cam.
  3. Clear the Code and Test Drive: After checking oil and OCVs, clear the code and drive the vehicle to see if it returns.
  4. Monitor Live Data: A scan tool capable of monitoring live data can show actual vs. desired camshaft angles, which can help pinpoint if the OCV is not responding correctly.

When to See a Shop:

If an oil change doesn't resolve the issue, or if you're uncomfortable testing the OCVs, it's best to take your Forester to a Subaru specialist. They have specific diagnostic procedures and tools to accurately test the AVCS components and determine if the issue is with an OCV, a cam phaser, or related oil pressure issues. Addressing this promptly is important to prevent potential engine damage or further performance degradation.

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