What causes a P109C code?

P109C 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 P109C code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P109C 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

P109C

High Pressure (dump) Valve current feedback min range fault

What it means

The ECM has detected that the electrical current returning from the fuel pressure relief valve is below the minimum expected threshold, indicating a circuit issue.