What causes a P1042 code?

P1042 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 P1042 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1042 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.

OBD-II

P1042

EMPCD P3 (exhaust air pressure before turbine) controller feedback monitor, inner clamping symptom

What it means

P1042 indicates that the Engine ECU has detected a mechanical blockage or 'clamping' of the exhaust pressure controller (VGT vanes). The actuator is attempting to move the vanes to manage boost, but the feedback sensor shows they are physically stuck or not reaching the commanded position.