U2171: Communication Link Failure Between Modules

Definition

The OBD2 code U2171: Communication Link Failure Between Modules indicates that there is a problem with the communication network between different electronic control modules in the vehicle, preventing them from exchanging data properly

Common causes

Faulty wiring or connectors
Damaged or corroded pins
Failed control module
Software issues or bugs
Poor ground connections
Intermittent electrical connections
Low battery voltage
Faulty communication network (CAN bus)

Common misdiagnoses

Faulty wiring or connectors
Defective control modules
Software issues or programming errors
Battery or power supply problems
Grounding issues
Intermittent communication issues
Faulty sensors or actuators
Corrupted data or signal interference

Troubleshooting steps

1. Check for Additional Codes

Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context about the issue
2. Inspect Wiring and Connectors
3. Visually inspect the wiring harnesses and connectors associated with the affected modules. Look for signs of damage, corrosion, or loose connections
4. Pay special attention to ground connections, as poor grounding can lead to communication issues
5. Check for Module Power Supply
6. Ensure that the affected modules are receiving the proper voltage and ground. Use a multimeter to check the power supply to the modules
7. If a module is not powered correctly, it may not communicate with other modules
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 the signal waveforms on the communication lines to ensure they are functioning correctly
11. Inspect for Short Circuits
12. Check for any short circuits in the wiring that could be causing interference with the communication signals
13. Look for pinched wires or damaged insulation that could lead to shorts
14. Check for Module Malfunction
15. If the wiring and connections are intact, the issue may be with one of the control modules themselves
16. If possible, swap the suspected module with a known good one to see if the problem persists
17. Reset the Modules
18. Sometimes, simply resetting the modules by disconnecting the battery for a few minutes can clear temporary communication issues
19. After reconnecting the battery, check if the code reappears
20. Update Software/Firmware
21. Check if there are any software or firmware updates available for the vehicle’s control modules. Sometimes, communication issues can be resolved with an update
22. Consult Technical Service Bulletins (TSBs)
23. Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have identified common issues and provided solutions
24. Professional Diagnosis
25. If the issue persists after performing the above steps, it may be necessary to seek help from a professional mechanic or dealership with advanced diagnostic tools. By following these steps, you can systematically identify and resolve the communication link failure indicated by the U2171 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Additional Codes

2. Inspect Wiring and Connectors

3. Visually inspect the wiring harnesses and connectors associated with the affected modules. Look for signs of damage, corrosion, or loose connections

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

5. Check for Module Power Supply

6. Ensure that the affected modules are receiving the proper voltage and ground. Use a multimeter to check the power supply to the modules

7. If a module is not powered correctly, it may not communicate with other modules

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 the signal waveforms on the communication lines to ensure they are functioning correctly

11. Inspect for Short Circuits

12. Check for any short circuits in the wiring that could be causing interference with the communication signals

13. Look for pinched wires or damaged insulation that could lead to shorts

14. Check for Module Malfunction

15. If the wiring and connections are intact, the issue may be with one of the control modules themselves

16. If possible, swap the suspected module with a known good one to see if the problem persists

17. Reset the Modules

18. Sometimes, simply resetting the modules by disconnecting the battery for a few minutes can clear temporary communication issues

19. After reconnecting the battery, check if the code reappears

20. Update Software/Firmware

21. Check if there are any software or firmware updates available for the vehicle’s control modules. Sometimes, communication issues can be resolved with an update

22. Consult Technical Service Bulletins (TSBs)

23. Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have identified common issues and provided solutions

24. Professional Diagnosis

25. If the issue persists after performing the above steps, it may be necessary to seek help from a professional mechanic or dealership with advanced diagnostic tools. By following these steps, you can systematically identify and resolve the communication link failure indicated by the U2171 code