What causes a SPN 4508 code?

SPN 4508 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 4508 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4508 active.

How do I fix SPN 4508?

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 4508

Allison transmission code P4508

What it means

Transmission Control Module (TCM) Input Power Signal - Loss of Power. This code indicates that the TCM detected a momentary or permanent loss of battery power to its memory or processor circuits while the ignition was ON.