P0278 Cylinder 6 Contribution/Balance Fault — Causes & Fix

What Does P0278 Mean?

P0278 means the ECU's cylinder-balance monitor detected that cylinder 6's contribution to crankshaft acceleration is outside the window it can correct with fuel trim. On common-rail diesels the dominant cause is an injector delivering too much or too little fuel — wear in the nozzle and control valve changes the delivered quantity even when the coil and circuit are fine.

P0278 at a Glance

• What it means: Cylinder 6 is producing noticeably more or less power than the others and the ECU can no longer balance it.
• Most common cause: Worn injector delivering the wrong fuel quantity — the classic cause on high-mileage diesels.
• Severity: Moderate — drivability suffers and the imbalance worsens as the injector wears.
• Can you drive?: Yes, short term, but fuel economy and smoothness degrade and DPF loading increases.
• Typical repair cost: £100-£350 per remanufactured injector fitted.