What causes a P1278 code?

P1278 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P1278 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1278 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

OBD-II

P1278

Increase in combustion in cylinder 6 relative to the others.

What it means

The Engine Control Module (ECM) has detected that Cylinder 6 is contributing significantly more power/combustion force to the crankshaft than the average of the other cylinders.