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P0597




DTC P0597-P0599

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0597
- Engine Coolant Thermostat Heater Control Circuit

DTC P0598
- Engine Coolant Thermostat Heater Control Circuit Low Voltage

DTC P0599
- Engine Coolant Thermostat Heater Control Circuit High Voltage

Diagnostic Fault Information






Circuit/System Description

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.

Conditions for Running the DTCs

* The ignition is ON, or the engine is running.

* The DTCs run continuously once the above condition is met

Conditions for Setting the DTC

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.

Action Taken When the DTC Sets

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

* The engine control module commands the engine cooling fans ON.

Conditions for Clearing the DTC

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

Diagnostic Aids

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).

Reference Information

Schematic Reference

Engine Controls Schematics [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON

2. Verify the parameters listed below do not display Malfunction when commanding the Engine Coolant Thermostat Heater ON and OFF with a scan tool.

* 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

• If Malfunction is displayed
Refer to Circuit/System Testing.

• If Malfunction is not displayed

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.

4. Verify the DTC does not set.

• If any DTC sets
Refer to Circuit/System Testing.

• If the DTC does not set

5. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the E41 engine coolant thermostat heater, Ignition ON.

2. Verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, remove the test lamp.

2. Test for less than 2 ohms in the ignition circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, remove the test lamp.

2. Test for infinite resistance between the ignition circuit and ground

• If less than infinite resistance, repair the short to ground in the circuit.

• If infinite resistance, test all the components connected to fuse and replace as necessary.

• If the test lamp illuminates

3. Verify that a test lamp does not illuminate between the ignition circuit terminal 1 and the control circuit terminal 2.

• If the test lamp illuminates

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K20 Engine Control Module.

• If the test lamp does not illuminate

4. Remove the test lamp.

5. Verify the scan tool E41 engine coolant thermostat heater Control Circuit High Voltage Test Status parameter is OK when commanding the E41 engine coolant thermostat heater ON with a scan tool.

• If OK is not displayed

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.

2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K20 Engine Control Module.

• If OK is not displayed

6. Install a 3 A fused jumper wire between the control circuit terminal 2 and the ignition circuit terminal 1.

7. Verify the scan tool E41 engine coolant thermostat heater Circuit High Voltage Test Status parameter is Malfunction when commanding the E41 engine coolant thermostat heater ON with a scan tool.

• If is not displayed Malfunction

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module

2. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms replace the K20 Engine Control Module

• If Malfunction is displayed

8. Test or replace the E41 engine coolant thermostat heater.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Engine Coolant Thermostat Replacement (LUV) Service and RepairEngine Coolant Thermostat Replacement (LUW) Service and Repair

* Control Module References Control Module References for ECM replacement, setup, and programming

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