U2928: Vehicle Communication Bus Malfunction

Definition

The OBD2 code U2928 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle

Common causes

Faulty wiring or connectors in the communication bus
Malfunctioning control modules
Corrupted software or firmware in control modules
Poor ground connections
Interference from aftermarket devices
Damaged or shorted communication lines
Low battery voltage or power supply issues
Faulty or damaged OBD-II port

Common misdiagnoses

Faulty Engine Control Module (ECM)
Defective Body Control Module (BCM)
Bad wiring or connectors
Malfunctioning sensors
Issues with the powertrain control module (PCM)
Incorrectly diagnosed transmission problems
Battery or charging system issues
Faulty diagnostic tools or software errors

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 problem
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections
4. Pay special attention to the connectors on the control modules, as well as any junction points in the wiring harness
5. Test the Communication Bus
6. Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage levels should be around 2.5V to 3.5V when the vehicle is on
7. Check for short circuits or open circuits in the communication lines
8. Check Control Modules
9. Ensure that all control modules are functioning properly. A malfunctioning module can disrupt communication on the bus
10. If possible, perform a software update on the control modules, as outdated software can sometimes cause communication issues
11. Inspect for Interference
12. Look for any aftermarket devices or modifications that may interfere with the vehicle's communication systems, such as alarms, remote starters, or audio systems
13. Check Battery and Ground Connections
14. Ensure that the vehicle's battery is in good condition and that all ground connections are secure. Poor power supply or grounding can lead to communication issues
15. Perform a Network Test
16. Some advanced scan tools can perform a network test to check the integrity of the communication bus. This can help identify which module may be causing the issue
17. Clear Codes and Test Drive
18. After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns
19. Consult Technical Service Bulletins (TSBs)
20. Check for any manufacturer-specific TSBs related to U2928 or communication issues. There may be known fixes or recalls that apply to your vehicle
21. Seek Professional Help
22. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2928 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 signs of damage, corrosion, or loose connections

4. Pay special attention to the connectors on the control modules, as well as any junction points in the wiring harness

5. Test the Communication Bus

6. Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage levels should be around 2.5V to 3.5V when the vehicle is on

7. Check for short circuits or open circuits in the communication lines

8. Check Control Modules

9. Ensure that all control modules are functioning properly. A malfunctioning module can disrupt communication on the bus

10. If possible, perform a software update on the control modules, as outdated software can sometimes cause communication issues

11. Inspect for Interference

12. Look for any aftermarket devices or modifications that may interfere with the vehicle's communication systems, such as alarms, remote starters, or audio systems

13. Check Battery and Ground Connections

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

15. Perform a Network Test

16. Some advanced scan tools can perform a network test to check the integrity of the communication bus. This can help identify which module may be causing the issue

17. Clear Codes and Test Drive

18. After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns

19. Consult Technical Service Bulletins (TSBs)

20. Check for any manufacturer-specific TSBs related to U2928 or communication issues. There may be known fixes or recalls that apply to your vehicle

21. Seek Professional Help

22. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2928 code