What causes a SPN 738 code?

SPN 738 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 SPN 738 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 738 active.

How do I fix SPN 738?

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

J1939 SPN

SPN 738

J1939 SPN 738 — Engine Management parameter

What it means

Engine Management Parameter Fault. This indicates a configuration error, data mismatch, or calibration corruption within the Engine Control Module (ECM).