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DTC P0597-P0599

The engine control module (ECM) controls the pulse width modulated (PWM) thermostat. The engine coolant thermostat heater controls coolant flow and regulates the engine operating temperature. The ECM supplies 12 V to the thermostat. The ECM controls the engine coolant thermostat heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.

The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 15 s.

DTC P0597 00, P0598 00, P0599 00 are Type B DTCs.

DTC P0597 00, P0598 00, P0599 00 are Type B DTCs.

The engine coolant thermostat heater has a mechanical fail-safe in case of an electrical condition with the engine coolant thermostat heater. The mechanical thermostat will open at approximately 104°C (220°F). The mechanical thermostat will cycle from approximately 104°C (220°F) to approximately 98°C (208°F). The heater is part of the thermostat. The engine coolant thermostat heater and the thermostat housing are serviced as an assembly.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

1. Ignition OFF, disconnect the harness connector at the E41 Engine Coolant Thermostat Heater.
2. Ignition ON, verify that a test lamp illuminates between the control circuit terminal 2 and ground.

⇒	If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

3. Verify that a test lamp does not illuminate between the control circuit terminal 1 and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

4. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
5. Test for infinite resistance between the control circuit terminal X2 10 and ground.

⇒	If less than the specified value, test the control circuit for a short to ground.

6. Test for less than 5 Ω between the control circuit terminal X2 70 at the K20 Engine Control Module harness connector and terminal 1 at the E41 Engine Coolant Thermostat Heater harness connector.

⇒	If greater than the specified value, test the control circuit for an open/high resistance.

7. If all circuits test normal, replace the E41 Engine Coolant Thermostat Heater.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.