P0590: Thermostat Heater Control Circuit Malfunction

Definition

The OBD2 code P0590 indicates a malfunction in the thermostat heater control circuit, which affects the operation of the engine's thermostat and can lead to improper engine temperature regulation

Common causes

Faulty thermostat
Damaged wiring or connectors
Short circuit in the heater control circuit
Open circuit in the heater control circuit
Failed engine control module (ECM)
Corroded terminals
Poor ground connection

Common misdiagnoses

Faulty thermostat
Engine coolant temperature sensor issues
Wiring or connector problems
Engine control module (ECM) failure
Cooling system leaks
Incorrect coolant type or level
Faulty radiator fan
Other sensor malfunctions (e.g., intake air temperature sensor)

Troubleshooting steps

1. Check for Additional Codes

Before proceeding, use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are other issues present
2. Inspect the Thermostat
3. Check the thermostat for any physical damage or signs of wear
4. Ensure that the thermostat is functioning properly. If it is stuck open or closed, it may need to be replaced
5. Examine the Wiring and Connectors
6. Inspect the wiring harness and connectors associated with the thermostat heater control circuit for any signs of damage, corrosion, or loose connections
7. Repair or replace any damaged wiring or connectors
8. Test the Thermostat Heater
9. Use a multimeter to test the resistance of the thermostat heater. Compare the readings to the specifications provided by the manufacturer
10. If the resistance is outside the specified range, the thermostat may need to be replaced
11. Check the Engine Coolant Temperature Sensor (ECT)
12. Inspect the ECT for proper operation. A faulty sensor can send incorrect signals to the engine control module (ECM), leading to thermostat control issues
13. Test the ECT with a multimeter and replace it if necessary
14. Inspect the Engine Control Module (ECM)
15. In rare cases, the ECM may be faulty or have a software issue. Check for any updates or reprogramming that may be needed
16. If all other components check out, consider having the ECM tested
17. Check for Short Circuits
18. Use a multimeter to check for short circuits in the thermostat heater control circuit. This includes checking for continuity and ensuring there are no unintended connections
19. Clear the Codes and Test Drive
20. After performing repairs, clear the trouble codes using the OBD-II scanner
21. Take the vehicle for a test drive to see if the code reappears. Monitor the engine temperature and thermostat operation during the drive
22. Consult Repair Manual
23. Refer to the vehicle's repair manual for specific diagnostic procedures and specifications related to the thermostat and its control circuit
24. Seek Professional Help
25. If the issue persists after performing these steps, it may be best to consult a professional mechanic for further diagnosis and repair. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0590 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Additional Codes

2. Inspect the Thermostat

3. Check the thermostat for any physical damage or signs of wear

4. Ensure that the thermostat is functioning properly. If it is stuck open or closed, it may need to be replaced

5. Examine the Wiring and Connectors

6. Inspect the wiring harness and connectors associated with the thermostat heater control circuit for any signs of damage, corrosion, or loose connections

7. Repair or replace any damaged wiring or connectors

8. Test the Thermostat Heater

9. Use a multimeter to test the resistance of the thermostat heater. Compare the readings to the specifications provided by the manufacturer

10. If the resistance is outside the specified range, the thermostat may need to be replaced

11. Check the Engine Coolant Temperature Sensor (ECT)

12. Inspect the ECT for proper operation. A faulty sensor can send incorrect signals to the engine control module (ECM), leading to thermostat control issues

13. Test the ECT with a multimeter and replace it if necessary

14. Inspect the Engine Control Module (ECM)

15. In rare cases, the ECM may be faulty or have a software issue. Check for any updates or reprogramming that may be needed

16. If all other components check out, consider having the ECM tested

17. Check for Short Circuits

18. Use a multimeter to check for short circuits in the thermostat heater control circuit. This includes checking for continuity and ensuring there are no unintended connections

19. Clear the Codes and Test Drive

20. After performing repairs, clear the trouble codes using the OBD-II scanner

21. Take the vehicle for a test drive to see if the code reappears. Monitor the engine temperature and thermostat operation during the drive

22. Consult Repair Manual

23. Refer to the vehicle's repair manual for specific diagnostic procedures and specifications related to the thermostat and its control circuit

24. Seek Professional Help

25. If the issue persists after performing these steps, it may be best to consult a professional mechanic for further diagnosis and repair. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the P0590 code