What causes a SPN 1786 code?

SPN 1786 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 1786 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 1786 active.

How do I fix SPN 1786?

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 1786

EGR Recirculation Temperature 2 High Signal

What it means

Indicates that the secondary Exhaust Gas Recirculation (EGR) temperature sensor has detected values above the maximum operating threshold, suggesting cooling failure or excessive exhaust heat.