What causes a P1263 code?

P1263 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 P1263 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1263 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

P1263

Increase in combustion in cylinder 1 relative to the others.

What it means

Detected increased power contribution or combustion pressure from Cylinder 1 compared to the average of the other cylinders.