Cylinder 5 Fuel Trim at Min Limit
The P02AB code indicates that the engine control module (ECM) has detected the fuel trim for cylinder 5 is at its minimum limit, meaning the system is adding as little fuel as possible to correct a rich condition. This can be caused by a stuck-open fuel injector, excessive fuel pressure, a faulty oxygen sensor, or a vacuum leak. The ECM continuously adjusts fuel delivery based on oxygen sensor readings; when it cannot lean the mixture enough, it sets this code.
1. Most Common Causes
- Cylinder 5 fuel injector stuck open or leaking internally
- Faulty upstream oxygen sensor (bank 2) providing incorrect or biased readings
- Malfunctioning MAP or MAF sensor causing incorrect air/fuel mixture calculations
- Excessively high fuel pressure due to a defective fuel pressure regulator
- Restricted airflow to cylinder 5 (e.g., intake valve, valve seat, or stem seal issues)
- Low compression in cylinder 5 (worn rings, leaking valves, or blown head gasket)
- Cylinder 5 injector wiring shorted to ground
- Internal ECM/PCM failure (less common)
2. Symptoms You Will Notice
- Check Engine Light on
- Rough idle or misfire
- Poor fuel economy
- Strong fuel smell from exhaust
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect fuel injector on cylinder 5 for leakage or sticking.
Step 3: Check fuel pressure with a gauge; compare to specs.
Step 4: Test oxygen sensor voltage and response time.
Step 5: Inspect for vacuum leaks using smoke machine or propane.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as a rich condition can damage the catalytic converter and oxygen sensors. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: injector replacement $200-$600, fuel pressure regulator $100-$300, oxygen sensor $100-$200.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.