What causes a SPN 45 code?

SPN 45 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 45 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 45 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

J1939 SPN

SPN 45

J1939 SPN 45 — Engine parameter

What it means

Intake Air Heater (IAH) Relay / Circuit Malfunction. This code indicates the ECM has detected a current out of range or a failure in the circuit that pre-heats the air entering the cylinders.