Volt

DTC P0597-P0599

The engine control module (ECM) controls the pulse width modulated (PWM) thermostat. The thermostat controls coolant flow and regulates the engine operating temperature. Ignition voltage is supplied directly to the thermostat. The ECM controls the thermostat 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 seconds.

DTCs P0597, P0598, and P0599 are Type B DTCs.

The thermostat has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will open at approximately 80°C (176°F). The mechanical thermostat will cycle from approximately 85°C (185°F) to approximately 102°C (215°F).

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Hybrid Modes of Operation Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, engine running, observe the DTC information with a scan tool. DTC P0685, P0689, P0690 or P1682 should not be set.

⇒	If a DTC is set, refer to DTC P0685, P0689, P0690, or P1682 .

2. Engine running, observe the following scan tool control circuit status parameters.

•	Engine Coolant Thermostat Heater Control Circuit Low Voltage Test Status

•	Engine Coolant Thermostat Heater Control Circuit Open Test Status

•	Engine Coolant Thermostat Heater Control Circuit High Voltage Test Status

Each parameter should display OK or Not Run.

3. 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. Service Mode active, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition circuit and replace as necessary.

3. Command the Engine Coolant Thermostat Heater to 10 % with a scan tool. Test for 2.5-3.5 V between the control circuit terminal 2 and ground.

⇒	If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the K20 ECM.

⇒	If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

4. Command the Engine Coolant Thermostat Heater to 100 % with a scan tool. The DMM should transition from 2.5-3.5 V when commanded to 10 % to less than 0.1 V when commanded to 100 %.

⇒	If the circuit voltage does not correspond to the specified values, replace the K20 ECM.

5. If all circuits test normal, test or replace the E41 engine coolant thermostat heater.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.