What causes a P1128 code?

P1128 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 P1128 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1128 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

P1128

Air temp too high

What it means

The Engine Control Module (ECM) has detected that the intake manifold air temperature or charge air temperature has exceeded the maximum safe operating threshold.