U1956: U1956: "Module Communication Failure

Definition

The OBD2 code U1956 indicates a "Module Communication Failure," meaning that there is a problem with communication between the vehicle's control modules, which may affect their ability to share data or function properly

Common causes

Faulty wiring or connectors
Malfunctioning control module
Poor ground connections
Corroded or damaged pins
Intermittent communication issues
Software or firmware issues
Low battery voltage
Electrical interference
Aftermarket modifications or installations
Faulty CAN bus system

Common misdiagnoses

Faulty wiring or connectors
Defective control module
Software issues or updates needed
Battery or power supply problems
Grounding issues
Intermittent communication issues
Other communication protocol failures

Troubleshooting steps

1. Check for Other Codes

Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the affected modules. Look for 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 affected modules are receiving the proper voltage. Use a multimeter to check the power supply to the modules
7. Verify that the fuses related to the communication network are intact
8. Test Communication Lines
9. Use a scan tool to check the communication lines (CAN bus, LIN bus, etc.) for continuity and proper voltage levels
10. If you have access to an oscilloscope, you can check for signal integrity on the communication lines
11. Inspect Modules
12. If possible, check the affected module for any signs of damage or malfunction. This may involve removing the module and inspecting it physically
13. If you suspect a module is faulty, you may need to replace it or reprogram it
14. Check for Interference
15. Look for any aftermarket devices or modifications that may interfere with the vehicle's communication network. This includes alarm systems, stereo systems, or other electronic devices
16. Perform a Network Test
17. Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly
18. Reset the System
19. After addressing any issues found, clear the trouble codes using the OBD-II scanner and see if the code returns after a test drive
20. Consult Technical Service Bulletins (TSBs)
21. Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common communication issues
22. Seek Professional Help
23. 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 underlying cause of the U1956 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 affected modules. Look for 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 affected modules are receiving the proper voltage. Use a multimeter to check the power supply to the modules

7. Verify that the fuses related to the communication network are intact

8. Test Communication Lines

9. Use a scan tool to check the communication lines (CAN bus, LIN bus, etc.) for continuity and proper voltage levels

10. If you have access to an oscilloscope, you can check for signal integrity on the communication lines

11. Inspect Modules

12. If possible, check the affected module for any signs of damage or malfunction. This may involve removing the module and inspecting it physically

13. If you suspect a module is faulty, you may need to replace it or reprogram it

14. Check for Interference

15. Look for any aftermarket devices or modifications that may interfere with the vehicle's communication network. This includes alarm systems, stereo systems, or other electronic devices

16. Perform a Network Test

17. Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly

18. Reset the System

19. After addressing any issues found, clear the trouble codes using the OBD-II scanner and see if the code returns after a test drive

20. Consult Technical Service Bulletins (TSBs)

21. Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common communication issues

22. Seek Professional Help

23. 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 underlying cause of the U1956 code