P0278: Cylinder-six balance should not be confused with an injector circuit test

P0278 identifies cylinder six contribution/balance. Ford’s cold-start example for the 6.7L engine sets this fault when fuel-balancing correction exceeds 90% of the allowed correction at the current operating point. The monitor concerns combustion-balancing control effort, not the injector IC’s open- or short-circuit classification.

Why supporting diagnostics matter

The cold monitor requires crankshaft-position circuit and range/performance checks to pass and fuel-balance wheel learning to be complete. Its speed and injection-quantity windows are 500–3,000 rpm and 3.5–90 mg/stroke, with a typical duration of 7.5 seconds.

Ford’s separate injector-circuit section illustrates the distinction: electrical output faults have their own code families and monitoring logic. If electrical faults accompany P0278, retain them as additional evidence rather than translating the balance code into an assumed circuit failure.

Match verification to the original event

The cold-start strategy is explicitly mode-dependent. Ford also describes general balancing, which excludes regeneration and uses additional supporting checks. A normal warm observation may help the investigation but does not automatically certify the earlier cold balancing condition.

Confirm the engine’s cylinder-six assignment before any physical diagnosis. The summary does not distinguish injector delivery, mechanical combustion quality, or other possible causes of the required correction. It supplies the monitored limit and prerequisites; a vehicle-specific diagnostic procedure is still needed to decide what, if anything, should be repaired or replaced.

Source and applicability

This explanation follows Ford’s 2023–2024 diesel OBD summary. Match the vehicle’s engine and calibration before applying these monitor values; a generic code alone does not establish fitment. Ford PDF, page 19 · Ford PDF, page 59 · Ford PDF, page 16.