What causes a P1879 code?

P1879 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 P1879 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1879 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

OBD-II

P1879

Coolant temperature sensor out of range high

What it means

The Engine Control Module (ECM) has detected a voltage signal from the Engine Coolant Temperature (ECT) sensor that is higher than the maximum allowable limit, indicating a short circuit or an extreme overheating condition.