What causes a SPN 5009 code?

SPN 5009 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 5009 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 5009 active.

How do I fix SPN 5009?

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 5009

Allison transmission code P5009

What it means

SPN 5009 corresponds to Allison DTC P0731: Gear 1 Incorrect Ratio. This indicates the Transmission Control Module (TCM) detected that the engine/input speed does not match the output speed for the commanded first gear.