What causes a P0599 code?

P0599 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 P0599 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0599 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

P0599

P0599 - Thermostat Heater Control Circuit High

What it means

The Engine Control Module (ECM) has detected a voltage level in the electronically controlled thermostat heater circuit that exceeds the calibrated limit, typically indicating an open circuit or internal short.