U1628: U1628: "Vehicle Communication Bus Malfunction

Definition

The OBD2 code U1628 indicates a malfunction in the vehicle communication bus, which affects the ability of various modules to communicate with each other

Common causes

Faulty OBD-II connector
Damaged wiring or connectors in the communication bus
Malfunctioning control modules
Poor ground connections
Corroded or loose terminals
Software issues or bugs in the control modules
Interference from aftermarket devices
Low battery voltage or power supply issues
Faulty CAN bus transceiver
Issues with the vehicle's body control module (BCM)

Common misdiagnoses

Faulty OBDII connector
Bad ground connections
Defective ECM (Engine Control Module)
Faulty wiring or harness issues
Malfunctioning CAN bus modules
Corrupted software or firmware in control modules
Battery or power supply issues
Faulty sensors or actuators
Intermittent communication issues
Incorrectly installed aftermarket accessories

Troubleshooting steps

1. Check for Other Codes

Use an OBD-II scanner to check for any additional trouble codes. Sometimes, other codes can provide context or lead to the root cause of the U1628 code
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for damaged, corroded, or loose connections
4. Pay special attention to the connectors on the Engine Control Module (ECM), Transmission Control Module (TCM), and any other modules that communicate over the bus
5. Check for Short Circuits
6. Use a multimeter to check for short circuits in the wiring. A short to ground or power can disrupt communication
7. Test the resistance of the communication lines to ensure they are within specifications
8. Test the Modules
9. If possible, test the individual control modules for proper operation. A malfunctioning module can cause communication issues
10. If you have access to a scan tool that can communicate with all modules, check if you can read data from each module
11. Inspect the CAN Bus Termination
12. Ensure that the CAN bus is properly terminated. There should be termination resistors at both ends of the bus. If these resistors are missing or faulty, it can lead to communication issues
13. Check for Interference
14. Look for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarm systems, stereo systems, or other electronic devices
15. Battery and Ground Connections
16. Ensure that the vehicle's battery is in good condition and that all ground connections are secure. Poor power or ground can lead to communication failures
17. Update Software/Firmware
18. Check if there are any software updates available for the vehicle's control modules. Sometimes, manufacturers release updates to fix known communication issues
19. Clear Codes and Test Drive
20. After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the U1628 code returns
21. If the issue persists, consult the vehicle's service manual for specific diagnostic procedures related to the communication bus and the modules involved. 1
22. Professional Diagnosis
23. If you are unable to resolve the issue, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1628 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 communication bus (CAN bus). Look for damaged, corroded, or loose connections

4. Pay special attention to the connectors on the Engine Control Module (ECM), Transmission Control Module (TCM), and any other modules that communicate over the bus

5. Check for Short Circuits

6. Use a multimeter to check for short circuits in the wiring. A short to ground or power can disrupt communication

7. Test the resistance of the communication lines to ensure they are within specifications

8. Test the Modules

9. If possible, test the individual control modules for proper operation. A malfunctioning module can cause communication issues

10. If you have access to a scan tool that can communicate with all modules, check if you can read data from each module

11. Inspect the CAN Bus Termination

12. Ensure that the CAN bus is properly terminated. There should be termination resistors at both ends of the bus. If these resistors are missing or faulty, it can lead to communication issues

13. Check for Interference

14. Look for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarm systems, stereo systems, or other electronic devices

15. Battery and Ground Connections

16. Ensure that the vehicle's battery is in good condition and that all ground connections are secure. Poor power or ground can lead to communication failures

17. Update Software/Firmware

18. Check if there are any software updates available for the vehicle's control modules. Sometimes, manufacturers release updates to fix known communication issues

19. Clear Codes and Test Drive

20. After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the U1628 code returns

21. If the issue persists, consult the vehicle's service manual for specific diagnostic procedures related to the communication bus and the modules involved. 1

22. Professional Diagnosis

23. If you are unable to resolve the issue, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1628 code