What causes a P156A code?

P156A 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 P156A code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P156A 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

P156A

Coolant Pump 1 PWM driver short open circuit

What it means

The ECM has detected an electrical discontinuity or a short circuit in the Pulse Width Modulation (PWM) control circuit for the primary electric coolant pump.