P0599 - THERMOSTAT HEATER CONTROL CIRCUIT HIGH

The main function of the thermostat heater is to constantly control the flow or passage of coolant. It also regulates the operating temperature of the engine. To perform these functions, the thermostat is supplied with 12 volts from the ECM (Engine Control Module), which is the power supply.

A malfunction of the engine thermostat results in the setting of various fault codes, which warn the driver of such a condition. Specifically, the P0599 OBD2 fault code is a generic code, which shows that the ECM found a high circuit in the thermostat heater.

• Illuminated Check Engine light.
• Temperatures displayed on the dash indicator are excessively high.

Reasons for storing the P0599 OBDII DTC:

• The thermostat may have damage to its electrical connector or thermostat wires.
• The radiator could be leaking coolant.
• There could be an open or short circuit between the ECM and the thermostat due to damage to the wiring harness.
• The thermostat may be faulty.

Steps to resolve the P0599 OBD2 diagnostic code:

• Check the radiator coolant level to verify that the radiator coolant level is within the necessary range. An adequate coolant level is required for the thermostat to perform properly, so make any necessary corrections for leaks or other damage.
• Check that the electrical components of the thermostat are in good condition. If you detect burnt wires or high levels of corrosion on the connectors, repair or, if necessary, replace them.
• Take a reading of the thermostat resistance. This result should match that specified in the service manual. If you detect an out-of-range resistance, follow the manufacturer's instructions for diagnosing the thermostat.