What causes a SPN 37 code?

SPN 37 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 37 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 37 active.

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 37

J1939 SPN 37 — Engine parameter

What it means

SPN 37 refers to the Air Pressure Control parameter. It indicates that the engine control module (ECM) has detected an abnormality in the management of the vehicle's compressed air system, typically specifically related to the governor or unloader circuit.