What causes a SPN 667 code?

SPN 667 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 667 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 667 active.

How do I fix SPN 667?

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 667

J1939 SPN 667 — Engine Management parameter

What it means

J1939 SPN 667 indicates an issue with the Engine Management Parameter (Auxiliary Input), which most manufacturers utilize to monitor the A/C Pressure switch or PTO engagement signal to the ECU.