What causes a P156D code?

P156D 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 P156D code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P156D 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

P156D

Coolant Pump 2 PWM driver short open circuit

What it means

The P156D code indicates that the Engine Control Module detected an electrical fault (open circuit or short) in the Pulse Width Modulation (PWM) signal circuit used to control the secondary electric coolant pump.