What causes a SPN 2004 code?

SPN 2004 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 2004 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 2004 active.

How do I fix SPN 2004?

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 2004

TSC1 (Transmission) Timeout

What it means

Indicates the ECU has lost communication with the transmission controller or the TSC1 message is not being received within the expected timeframe.