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.
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 104°C (220°F). The mechanical thermostat will cycle from approximately 104°C (220°F) to approximately 98°C (208°F).
Reference Information
Schematic Reference
Engine Cooling Schematics (Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
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 (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. DTC P0689 and P1682 should not be set.
• If a DTC is set, refer to DTC P0685, P0689, or P0690 (P0685).
2. Ignition ON, observe the following scan tool control circuit status parameters.
* Eng Clnt Therm Htr Ckt Short Gnd Test Status
* Eng Clnt Therm Htr Ckt Open Test Status
* Eng Clnt Therm Htr Ckt Short Volts 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.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the engine coolant thermostat heater.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 2 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 percent with a scan tool. Test for 2.5-3.5 V between the control circuit terminal 1 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 ECM.
• If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Command the engine coolant thermostat heater to 100 percent with a scan tool. The DMM should transition from 2.5-3.5 V when commanded to 10 percent to less than 0.1 V when commanded to 100 percent.
• If the circuit voltage does not correspond to the specified values, replace the ECM.
5. If all circuits test normal, test or replace the engine coolant thermostat heater.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Engine Coolant Thermostat Replacement (1.2L DOHC) (Service and Repair)Engine Coolant Thermostat Replacement (1.5L) (Service and Repair)Engine Coolant Thermostat Replacement (1.4L LDT/1.6 LXV) (Service and Repair)Engine Coolant Thermostat Replacement (1.4L/1.6L DOHC) (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming