Code
P0278
GWM
P — Powertrain
- 6 cylinder is incorrectly balanced
AI status
Completed
Completed
100%
Causes
- Faulty or leaking fuel injector on cylinder 6
- Ignition system fault (coil, spark plug, plug wire) for cylinder 6
- Low or inconsistent cylinder compression (mechanical issue)
- Vacuum or intake leak affecting cylinder 6
- Fuel delivery or fuel pressure issues
- Wiring or connector fault to injector or ignition coil
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or vibration
- Misfire felt under load or at idle (often logged as misfire on cylinder 6)
- Reduced engine power and acceleration
- Poor fuel economy and increased emissions
- Possible fuel smell or smoke if injector is leaking
What to check
- Read stored and pending codes and view freeze-frame data with a scan tool
- Check misfire counts and cylinder contribution/imbalance values in live data
- Visually inspect ignition components (coil, plug, boots) on cylinder 6
- Inspect fuel injector wiring and connector for damage or corrosion
- Check fuel pressure at the rail (static and under cranking/loaded conditions)
- Perform a quick compression or relative compression test on cylinder 6
Signal parameters
- Cylinder contribution percentage or cylinder balance values (scan-tool specific)
- Misfire counters (per-cylinder misfire count)
- Injector pulse width (ms) and commanded injector duty
- Short-term and long-term fuel trim (STFT / LTFT)
- Fuel rail pressure (kPa or bar)
- RPM, cam and crank position correlation
Diagnostic algorithm
- Retrieve codes, freeze-frame and live data. Note misfire counts and fuel trim values. Check for related codes (injector, ignition, fuel trim, cam/crank).
- Perform a visual inspection: spark plug condition, coil/boot damage, wiring/connectors at injector and coil, signs of fuel leak or oil contamination.
- Use a scan tool cylinder contribution or balance test to confirm reduced contribution from cylinder 6.
- Swap ignition coil (or coil-on-plug) from cylinder 6 with another cylinder and re-run the contribution/misfire test. If the fault moves, replace the coil.
- Swap the fuel injector from cylinder 6 with another cylinder (if practical) and re-check. If the imbalance follows the injector, replace the injector.
- Check fuel rail pressure and regulator operation to ensure adequate supply. Inspect for restricted fuel flow to the affected injector.
- Perform a cylinder compression and/or leak-down test on cylinder 6 and compare to other cylinders. Repair as needed for low compression (rings, valves, head gasket).
- Smoke test or use a vacuum gauge to detect intake manifold or vacuum leaks affecting cylinder 6.
- Inspect cam/crank timing and camshaft actuator operation if timing-related symptoms or correlated cam/crank codes are present.
- Check wiring resistance and continuity between injector/coil connectors and the PCM, and inspect for corrosion or pins pushed out.
- After repairs, clear codes and road-test with a scan tool connected to verify the cylinder contribution is within expected range and that no new codes return.
- If all mechanical and electrical tests pass and the issue persists, consider ECM software update or replacement as a last resort.
Likely causes
- Clogged or leaking injector on cylinder 6
- Failed ignition coil or fouled spark plug on cylinder 6
- Low compression due to worn rings, burned valve, or head gasket leak at cylinder 6
- Open or shorted injector wiring or corroded connector at cylinder 6
- Intake manifold gasket leak or port leak near cylinder 6
- Weak fuel rail pressure reducing injector pulse effectiveness
Fault status
Status
P0278 — Cylinder 6 Incorrect Cylinder Balance (cylinder 6 contribution out of range).
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email