What causes a SPN 4200 code?

SPN 4200 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 4200 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4200 active.

How do I fix SPN 4200?

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 4200

Allison transmission code P4200

What it means

Output Speed Sensor (OSS) Signal Performance/Rationality/Missing. The Transmission Control Module (TCM) is detecting an erratic or missing signal from the output speed sensor relative to engine speed and input speed.