Cylinder 8 Fuel Trim at Max Limit
The P02B6 code indicates that the engine control module (ECM) has detected that the fuel trim for cylinder 8 has reached its maximum adjustment limit, meaning the system is adding as much fuel as possible to compensate for a lean condition. This can be caused by a vacuum leak, fuel injector issue, or mechanical problem specific to cylinder 8, leading to an air-fuel mixture that is too lean.
1. Most Common Causes
- Vacuum leak near cylinder 8 intake runner
- Clogged or faulty fuel injector on cylinder 8
- Low fuel pressure or failing fuel pump
- Intake manifold gasket leak
- Exhaust leak before oxygen sensor
- Faulty oxygen sensor or MAF sensor
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or misfire on cylinder 8
- Poor fuel economy
- Hesitation or lack of power during acceleration
- Possible engine knocking or pinging
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Inspect for vacuum leaks using a smoke machine near cylinder 8 intake.
Step 3: Check fuel injector pulse and resistance on cylinder 8; swap injector to see if code follows.
Step 4: Perform a fuel pressure test to ensure proper pressure and volume.
Step 5: Inspect spark plug and ignition coil on cylinder 8 for fouling or damage.
Step 6: Check for exhaust leaks before the oxygen sensor that could cause false lean readings.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the lean condition can cause engine damage, including overheating or catalytic converter failure. Short trips to a repair shop are acceptable if the engine is not misfiring severely.
How much does it cost to fix?▼
The cost varies depending on the root cause. A simple vacuum leak repair may cost $150-$200, while replacing a fuel injector can range from $200-$400. Diagnostic fees are typically $100-$150.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.