What causes a P0668 code?

P0668 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 P0668 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0668 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

P0668

PCM/ECM Internal Temperature Sensor Circuit Low

What it means

The engine control module (ECM) provides an internal monitoring circuit for heat; P0668 indicates an extremely low voltage signal, typically signaling a short to ground or internal component failure within the control module.