U2606: CAN Bus Communication Fault

Definition

The OBD2 code U2606: CAN Bus Communication Fault indicates a malfunction in the Controller Area Network (CAN) communication system, which may involve issues with data transmission between various vehicle modules

Common causes

Faulty CAN bus wiring or connectors
Short circuit in the CAN bus
Open circuit in the CAN bus
Faulty or malfunctioning ECU (Electronic Control Unit)
Interference from other electrical components
Corroded or damaged connectors
Poor ground connections
Faulty CAN bus transceiver
Software issues or bugs in the ECU
Incompatible aftermarket components or modifications

Common misdiagnoses

Faulty Engine Control Module (ECM)
Defective Body Control Module (BCM)
Bad wiring or connectors
Faulty sensors
Powertrain Control Module (PCM) issues
Battery or charging system problems
Grounding issues
Faulty CAN Bus transceiver
Software or firmware issues
Intermittent electrical connections

Troubleshooting steps

1. Check for Other Codes

Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate which module is having issues
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the CAN bus. Look for damaged, frayed, or corroded wires and loose or corroded connectors
4. Pay special attention to the connectors on the modules that are part of the CAN network
5. Check for Short Circuits
6. Use a multimeter to check for short circuits between the CAN high (usually a green wire) and CAN low (usually a yellow wire) lines
7. Ensure that there are no shorts to ground or power
8. Test the CAN Bus Voltage
9. Measure the voltage on the CAN high and CAN low lines with the ignition on (engine off). The typical voltage levels should be around 2.5V to 2.8V for both lines
10. If the voltage is significantly off, it may indicate a problem with the bus or a module
11. Check Termination Resistors
12. Ensure that the CAN bus has the correct termination resistors (typically 120 ohms) at both ends of the bus. A missing or faulty resistor can cause communication issues
13. Inspect Modules
14. Identify which modules are connected to the CAN bus and check for any signs of failure. A malfunctioning module can disrupt communication
15. If possible, disconnect modules one at a time to see if the code clears or if communication is restored
16. Scan for Module Communication
17. Use a scan tool to check if all modules on the CAN bus are communicating properly. Some advanced scan tools can perform a network test to identify communication issues
18. Check for Interference
19. Look for any aftermarket devices or modifications that may interfere with the CAN bus communication, such as alarms, remote starters, or audio systems
20. Update or Reprogram Modules
21. In some cases, updating or reprogramming the affected modules may resolve communication issues. Check with the manufacturer for any available updates
22. Consult Technical Service Bulletins (TSBs)
23. Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have identified common issues and provided solutions. 1
24. Professional Diagnosis
25. If the issue persists after performing these steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing CAN bus issues. By following these steps, you should be able to identify and resolve the cause of the U2606 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 CAN bus. Look for damaged, frayed, or corroded wires and loose or corroded connectors

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

5. Check for Short Circuits

6. Use a multimeter to check for short circuits between the CAN high (usually a green wire) and CAN low (usually a yellow wire) lines

7. Ensure that there are no shorts to ground or power

8. Test the CAN Bus Voltage

9. Measure the voltage on the CAN high and CAN low lines with the ignition on (engine off). The typical voltage levels should be around 2.5V to 2.8V for both lines

10. If the voltage is significantly off, it may indicate a problem with the bus or a module

11. Check Termination Resistors

12. Ensure that the CAN bus has the correct termination resistors (typically 120 ohms) at both ends of the bus. A missing or faulty resistor can cause communication issues

13. Inspect Modules

14. Identify which modules are connected to the CAN bus and check for any signs of failure. A malfunctioning module can disrupt communication

15. If possible, disconnect modules one at a time to see if the code clears or if communication is restored

16. Scan for Module Communication

17. Use a scan tool to check if all modules on the CAN bus are communicating properly. Some advanced scan tools can perform a network test to identify communication issues

18. Check for Interference

19. Look for any aftermarket devices or modifications that may interfere with the CAN bus communication, such as alarms, remote starters, or audio systems

20. Update or Reprogram Modules

21. In some cases, updating or reprogramming the affected modules may resolve communication issues. Check with the manufacturer for any available updates

22. Consult Technical Service Bulletins (TSBs)

23. Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have identified common issues and provided solutions. 1

24. Professional Diagnosis

25. If the issue persists after performing these steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing CAN bus issues. By following these steps, you should be able to identify and resolve the cause of the U2606 code