What causes a P104C code?

P104C 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 P104C code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P104C 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

P104C

APSPD P2 (boost air pressure) sensor plausibility fault (low threshold)

What it means

The Engine Control Module (ECM) has detected that the boost pressure sensor reading at a specific stage (P2) is lower than the expected physical range or lower than the atmospheric pressure sensor reading under specific operating conditions.