P0278
Cylinder 6 Contribution/Balance
The appearance of the standard OBD2 trouble fault code P0278 is an indicator that your vehicle ECU triggered a threshold alert for "Cylinder 6 Contribution/Balance". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
A P0278 fault code points directly to a problem with cylinder 6 contribution/balance that the ECM has confirmed over multiple drive cycles. The most common signs are rough idle, hesitation, check engine light. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Rough idle, hesitation, check engine light
Common Causes
- Defective fuel injector Cyl 6
- Bad spark plug or wire
- Worn camshaft lobe
- Low compression
How to Fix
- 1 Test and replace fuel injector
- 2 Replace ignition components
- 3 Inspect camshaft
- 4 Run compression test
Technical Explanation
P0278 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
An active P0278 code under high-severity conditions means the affected system is operating outside safe parameters. Continued driving — especially under load or at highway speeds — significantly increases the risk of secondary damage to components like bad spark plug or wire.
Mechanic's Pro Tip
When diagnosing P0278, always test fuel volume delivery in addition to static pressure — a pump that holds pressure at idle but delivers insufficient volume under load will cause the fault only during acceleration or high demand, making it difficult to replicate in the driveway. Use a fuel pressure gauge with a volume outlet port: a healthy pump should deliver at least 1 liter per minute. Replace the fuel filter first; it's the cheapest test and solves the fault in a significant percentage of cases.
Injector: 150 - 400; Camshaft: 800+