U1520: U1520: Body Control Module Communication Error

Definition

The OBD2 code U1520 indicates a communication error between the Body Control Module (BCM) and other modules in the vehicle, suggesting a potential issue with wiring, connectors, or the BCM itself

Common causes

Faulty Body Control Module (BCM)
Poor electrical connections or wiring issues
Corroded connectors
Faulty or damaged CAN bus wiring
Malfunctioning or incompatible modules
Software or firmware issues
Low battery voltage or power supply problems
Interference from aftermarket accessories or modifications

Common misdiagnoses

Faulty Body Control Module (BCM)
Wiring issues or short circuits
Corrupted software or firmware in the BCM
Faulty connectors or terminals
Issues with other control modules (e.g., Engine Control Module)
Battery or charging system problems
Grounding issues
Faulty sensors related to the BCM
Communication network issues (e.g., CAN bus problems)

Troubleshooting steps

1. Check for Other Codes

Use an OBD-II scanner to check for any additional trouble codes. Sometimes, related codes can provide more context for the issue
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the BCM and other modules for any signs of damage, corrosion, or loose connections
4. Pay special attention to the ground connections, as poor grounding can lead to communication issues
5. Check Power Supply
6. Ensure that the BCM is receiving the correct voltage and ground. Use a multimeter to check the power supply to the BCM
7. Look for blown fuses that may affect the BCM or related circuits
8. Test the BCM
9. If possible, test the BCM for proper operation. This may involve using a scan tool to check for BCM functionality or replacing it with a known good unit to see if the problem persists
10. Inspect Other Modules
11. Check the other modules that communicate with the BCM. If one of these modules is malfunctioning, it can cause communication errors
12. Look for any signs of damage or issues with the wiring harnesses connecting these modules
13. Perform a Network Test
14. Use a scan tool capable of performing a network test to check for communication between the BCM and other modules. This can help identify if the issue is isolated to the BCM or if it involves other components
15. Clear Codes and Test Drive
16. After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the code reappears
17. Check for Software Updates
18. Sometimes, communication issues can be resolved with a software update for the BCM or other modules. Check with the manufacturer for any available updates
19. Consult Technical Service Bulletins (TSBs)
20. Look for any TSBs related to the U1520 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known fixes for this issue
21. Seek Professional Help
22. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these steps, you can systematically identify and resolve the communication error associated with the U1520 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Other Codes

2. Inspect Wiring and Connectors

3. Visually inspect the wiring and connectors associated with the BCM and other modules for any signs of damage, corrosion, or loose connections

4. Pay special attention to the ground connections, as poor grounding can lead to communication issues

5. Check Power Supply

6. Ensure that the BCM is receiving the correct voltage and ground. Use a multimeter to check the power supply to the BCM

7. Look for blown fuses that may affect the BCM or related circuits

8. Test the BCM

9. If possible, test the BCM for proper operation. This may involve using a scan tool to check for BCM functionality or replacing it with a known good unit to see if the problem persists

10. Inspect Other Modules

11. Check the other modules that communicate with the BCM. If one of these modules is malfunctioning, it can cause communication errors

12. Look for any signs of damage or issues with the wiring harnesses connecting these modules

13. Perform a Network Test

14. Use a scan tool capable of performing a network test to check for communication between the BCM and other modules. This can help identify if the issue is isolated to the BCM or if it involves other components

15. Clear Codes and Test Drive

16. After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the code reappears

17. Check for Software Updates

18. Sometimes, communication issues can be resolved with a software update for the BCM or other modules. Check with the manufacturer for any available updates

19. Consult Technical Service Bulletins (TSBs)

20. Look for any TSBs related to the U1520 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known fixes for this issue

21. Seek Professional Help

22. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these steps, you can systematically identify and resolve the communication error associated with the U1520 code