U1255: Manufacturer Specific Communication Bus Fault

Definition

The OBD2 code U1255 indicates a fault in the manufacturer-specific communication bus, suggesting a problem with data transmission between modules in the vehicle's network

Common causes

Faulty wiring or connectors in the communication bus
Malfunctioning control modules
Poor ground connections
Corroded or damaged terminals
Interference from aftermarket devices
Software issues or bugs in the control modules
Low battery voltage or power supply issues

Common misdiagnoses

Faulty Engine Control Module (ECM)
Bad wiring or connectors
Faulty Body Control Module (BCM)
Incorrectly installed aftermarket accessories
Faulty communication network components
Low battery voltage or poor battery connections
Faulty sensors or actuators
Software issues or outdated firmware
Grounding issues
Intermittent faults in the communication bus

Troubleshooting steps

1. Check for Other Codes

Use an OBD-II scanner to check for any additional trouble codes. Sometimes, U1255 may be accompanied by other codes that can provide more context about the issue
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the communication bus (CAN bus, LIN bus, etc.). Look for signs of damage, corrosion, or loose connections
4. Pay special attention to the connectors of the modules that are part of the communication network
5. Check for Short Circuits
6. Use a multimeter to check for short circuits in the communication lines. Ensure that the wires are not shorted to ground or to each other
7. Test the Modules
8. If you suspect a specific module is causing the issue, you can test it by disconnecting it and checking if the code persists. If the code goes away, the module may be faulty
9. Reconnect the module and check for proper operation
10. Inspect the Communication Bus
11. Use a scan tool that can monitor the communication bus. Check for any irregularities in the data being transmitted between modules
12. Look for any modules that are not responding or are showing unusual behavior
13. Check Power and Ground
14. Ensure that all modules on the communication bus have proper power and ground connections. A lack of power or a poor ground can cause communication issues
15. Update Software/Firmware
16. Check if there are any software or firmware updates available for the vehicle's modules. Sometimes, manufacturers release updates to fix communication issues
17. Clear Codes and Test Drive
18. After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns
19. Consult Manufacturer Documentation
20. Refer to the vehicle's service manual or manufacturer-specific documentation for any additional troubleshooting steps or specific tests related to the U1255 code
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 has experience with the specific make and model of your vehicle. By following these steps, you should be able to identify and resolve the underlying issue causing the U1255 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, LIN bus, etc.). Look for signs of damage, corrosion, or loose connections

4. Pay special attention to the connectors of the modules that are part of the communication network

5. Check for Short Circuits

6. Use a multimeter to check for short circuits in the communication lines. Ensure that the wires are not shorted to ground or to each other

7. Test the Modules

8. If you suspect a specific module is causing the issue, you can test it by disconnecting it and checking if the code persists. If the code goes away, the module may be faulty

9. Reconnect the module and check for proper operation

10. Inspect the Communication Bus

11. Use a scan tool that can monitor the communication bus. Check for any irregularities in the data being transmitted between modules

12. Look for any modules that are not responding or are showing unusual behavior

13. Check Power and Ground

14. Ensure that all modules on the communication bus have proper power and ground connections. A lack of power or a poor ground can cause communication issues

15. Update Software/Firmware

16. Check if there are any software or firmware updates available for the vehicle's modules. Sometimes, manufacturers release updates to fix communication issues

17. Clear Codes and Test Drive

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

19. Consult Manufacturer Documentation

20. Refer to the vehicle's service manual or manufacturer-specific documentation for any additional troubleshooting steps or specific tests related to the U1255 code

21. Seek Professional Help