What causes a SPN 4608 code?

SPN 4608 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 4608 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4608 active.

How do I fix SPN 4608?

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 4608

Allison transmission code P4608

What it means

Ignition Signal Voltage Low - The TCM has detected that the ignition voltage input is below a functional threshold while the main battery power is present.