What causes a P138A code?

P138A 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 P138A code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P138A 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

P138A

Control error discharge pos when low pressure supply insufficient

What it means

Aftertreatment Hydrocarbon Doser Fuel Pressure - Low Pressure Supply Insufficient. The engine controller detected that the fuel pressure required for an active regeneration was not met during a discharge attempt.