Cylinder 6 Contribution/Balance Fault
P0278 indicates that cylinder 6 is not contributing its fair share of power to the engine, meaning it's producing less combustion force than the other cylinders. This is typically caused by fuel delivery issues to that cylinder, such as a failing injector or fuel supply problem, rather than an ignition system fault.
What You Might Notice
- Check engine light illuminated with code P0278
- Reduced engine power and acceleration
- Rough idle or engine hesitation
- Decreased fuel economy
- Engine may vibrate or feel unbalanced under load
Most Common Causes
- 1
Faulty fuel injector cylinder 6
The injector may be partially clogged, dribbling fuel instead of spraying properly, or failed completely. This results in insufficient fuel delivery to that cylinder.
- 2
Fuel supply restriction to cylinder 6
A clogged fuel line, faulty fuel pressure regulator, or weak fuel pump may not deliver adequate fuel pressure to the number 6 cylinder fuel injector.
- 3
Compression loss in cylinder 6
Worn piston rings, a cracked piston, or leaking valves in cylinder 6 can reduce combustion efficiency and power output.
- 4
Ignition system failure on cylinder 6
A failing spark plug, ignition coil, or wiring issue specific to cylinder 6 can prevent proper ignition despite fuel delivery.
How to Diagnose It
- 1
Check Faulty fuel injector cylinder 6 — The injector may be partially clogged, dribbling fuel instead of spraying properly, or failed completely. This results in insufficient fuel delivery to that cylinder.
- 2
Check Fuel supply restriction to cylinder 6 — A clogged fuel line, faulty fuel pressure regulator, or weak fuel pump may not deliver adequate fuel pressure to the number 6 cylinder fuel injector.
- 3
Check Compression loss in cylinder 6 — Worn piston rings, a cracked piston, or leaking valves in cylinder 6 can reduce combustion efficiency and power output.
- 4
Check Ignition system failure on cylinder 6 — A failing spark plug, ignition coil, or wiring issue specific to cylinder 6 can prevent proper ignition despite fuel delivery.
How to Fix It
- 1
Clean or replace fuel injector cylinder 6
Remove and inspect the fuel injector for cylinder 6. Clean it with fuel injector cleaner or have it professionally cleaned; if it cannot be restored, replace with a new OEM injector.
- 2
Check and restore fuel pressure
Test fuel pressure with a gauge at idle and under load. If pressure is low, inspect the fuel pump, fuel filter, and pressure regulator. Replace any failing component.
- 3
Inspect cylinder 6 ignition system
Test the spark plug, ignition coil, and wiring harness for cylinder 6. Replace any worn spark plugs or failed coil packs.
- 4
Test cylinder compression
Perform a compression test on cylinder 6 to check for internal engine damage. Low compression indicates piston, ring, or valve problems requiring engine work.
Need a deeper diagnosis?
Search for related repair guides or browse by system.