P21A4/008612
From Ross-Tech Wiki
P21A4/008612-Fuel/Air Mixture Cylinder 9: Unbalanced
Possible Symptoms
- Engine runs rough
- Hesitation or lack of power
- Increased fuel consumption
- Illuminated MIL (Malfunction Indicator Light)
Possible Causes
- Spark plugs fouled or worn
- Intake system leaks (false air)
- Fuel pressure or fuel delivery issues
- Faulty fuel injector(s)
- Faulty ignition coil(s)
Possible Solutions
- Visually inspect and replace spark plugs if necessary
- Inspect intake system for leaks and repair as needed
- Check and verify correct fuel pressure and delivery quantity
- Inspect and clean or replace fuel injectors
- Check ignition coils, swap coils location to see if the fault code changes
Special Notes
- As per the Factory Repair manuals:
- This fault code sets when a specific cylinder runs too lean, causing an imbalance in the air-fuel mixture and engine roughness."
- Fault may be more prevalent in conditions such as:
- Engine speed between 1,240 – 2,240 RPM
- Engine load between 39.80 – 99.80%
- Cylinder head ECT > 60°C
- Modeled catalyst temperature between 450 – 850°C
- Lambda control in closed-loop operation
- No rough road detected
- Integrated air mass within 1.70 – 3.50 kg range