What causes a SPN 8 code?

SPN 8 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 8 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 8 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 8

J1939 SPN 8 — Engine parameter

What it means

SPN 8 typically refers to Brake Application Pressure or a related braking/timing parameter transmitted over the J1939 network. It indicates the engine controller is receiving invalid data or no data regarding the service brake application.