P1477: Additional Fan Relay Circuit Malfunction

Definition

The OBD2 code P1477 indicates a malfunction in the additional fan relay circuit, which may affect the operation of the vehicle's cooling fan system

Common causes

Faulty additional fan relay
Wiring issues (shorts, opens, or corrosion)
Bad connection or connector issues
Faulty additional cooling fan
Malfunctioning engine control module (ECM)
Blown fuse related to the fan circuit
Overheating engine or cooling system issues

Common misdiagnoses

Faulty cooling fan
Bad temperature sensor
Wiring issues or shorts
Malfunctioning engine control module (ECM)
Faulty relay
Incorrectly installed or damaged fan assembly
Air conditioning system issues
Low coolant levels or leaks

Troubleshooting steps

1. Check the Code

Use an OBD-II scanner to confirm the P1477 code and check for any additional codes that may provide more context about the issue
2. Inspect the Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the additional fan relay. Look for signs of damage, corrosion, or loose connections
4. Ensure that all connectors are securely attached and free of dirt or moisture
5. Test the Additional Fan Relay
6. Locate the additional fan relay in the fuse box or relay panel
7. Swap the relay with a similar one (if available) to see if the problem persists. If the fan operates with the swapped relay, the original relay may be faulty
8. Use a multimeter to test the relay for continuity and proper operation
9. Check the Fan Operation
10. Manually activate the fan by applying power directly to it to ensure that the fan itself is functioning correctly
11. If the fan does not operate when powered directly, it may need to be replaced
12. Inspect the Cooling System
13. Check the coolant level and ensure there are no leaks in the cooling system
14. Inspect the thermostat to ensure it is functioning properly, as an overheating engine can cause the additional fan to engage
15. Test the Control Circuit
16. Use a multimeter to check for voltage at the relay connector when the engine is running and the conditions for fan operation are met (e.g., high engine temperature or A/C on)
17. If there is no voltage, trace the wiring back to the engine control module (ECM) to identify any breaks or shorts
18. Check the Engine Control Module (ECM)
19. If all other components are functioning correctly, the issue may lie with the ECM. Check for any software updates or reprogramming that may be needed
20. In some cases, the ECM may need to be tested or replaced if it is not sending the correct signals to the relay
21. Clear the Codes and Test Drive
22. After performing repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code reappears
23. Consult a Professional
24. If the issue persists after following 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 P1477 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check the Code

2. Inspect the Wiring and Connectors

3. Visually inspect the wiring and connectors associated with the additional fan relay. Look for signs of damage, corrosion, or loose connections

4. Ensure that all connectors are securely attached and free of dirt or moisture

5. Test the Additional Fan Relay

6. Locate the additional fan relay in the fuse box or relay panel

7. Swap the relay with a similar one (if available) to see if the problem persists. If the fan operates with the swapped relay, the original relay may be faulty

8. Use a multimeter to test the relay for continuity and proper operation

9. Check the Fan Operation

10. Manually activate the fan by applying power directly to it to ensure that the fan itself is functioning correctly

11. If the fan does not operate when powered directly, it may need to be replaced

12. Inspect the Cooling System

13. Check the coolant level and ensure there are no leaks in the cooling system

14. Inspect the thermostat to ensure it is functioning properly, as an overheating engine can cause the additional fan to engage

15. Test the Control Circuit

16. Use a multimeter to check for voltage at the relay connector when the engine is running and the conditions for fan operation are met (e.g., high engine temperature or A/C on)

17. If there is no voltage, trace the wiring back to the engine control module (ECM) to identify any breaks or shorts

18. Check the Engine Control Module (ECM)

19. If all other components are functioning correctly, the issue may lie with the ECM. Check for any software updates or reprogramming that may be needed

20. In some cases, the ECM may need to be tested or replaced if it is not sending the correct signals to the relay

21. Clear the Codes and Test Drive

22. After performing repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code reappears

23. Consult a Professional

24. If the issue persists after following 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 P1477 code