What causes a P104B code?

P104B 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 P104B code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P104B 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

P104B

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

What it means

The Engine Control Module (ECM) detects that the Boost Pressure Sensor (P2) signal is higher than the expected physical limit or inconsistent with other pressure sensors (like Barometric or Intake Manifold Pressure) during key-on or specific load conditions.