Cylinder 6 Contribution/Balance Fault
The P0278 code indicates that the Engine Control Module (ECM) has detected a lack of contribution from cylinder 6 during the power balance test. This means cylinder 6 is not producing as much power as the other cylinders, often due to fuel delivery issues, ignition problems, or mechanical faults. The ECM monitors crankshaft acceleration to identify weak cylinders.
1. Most Common Causes
- Faulty fuel injector on cylinder 6 (electrical or clogged)
- Low compression in cylinder 6 (rings, valves, head gasket)
- Vacuum leak specific to cylinder 6
- Wiring or connector issues for injector 6
- Internal engine mechanical failure (camshaft, lifters, piston)
- Defective PCM (rare)
2. Symptoms You Will Notice
- Engine misfire or rough idle
- Check Engine Light illuminated
- Reduced engine power and acceleration
- Increased fuel consumption
- Engine vibration at idle
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Perform a power balance test to confirm cylinder 6 is weak.
Step 3: Inspect spark plug and ignition coil on cylinder 6; swap with another cylinder to see if misfire moves.
Step 4: Check fuel injector on cylinder 6; listen for clicking or swap injectors.
Step 5: Perform a compression test on cylinder 6 and compare to others.
Step 6: Inspect for vacuum leaks using a smoke machine.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause catalytic converter damage and reduced fuel economy. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
Costs vary: a spark plug replacement is $50-$150, a fuel injector replacement is $150-$400, and a compression repair can be $500-$1500.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.