What causes a SPN 4907 code?

SPN 4907 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 4907 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4907 active.

How do I fix SPN 4907?

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 4907

Allison transmission code P4907

What it means

Shift System - Ratio Inconsistency. This code indicates that the TCM has detected a discrepancy between the commanded gear ratio and the actual output speed, specifically related to internal pressure regulation during shifts.