U1859 – Module Communication Failure

The ODBII code U1859 indicates a “Module Communication Failure,” meaning there is a problem with communication between various control modules in the vehicle’s network.

The severity of ODBII code U1859 is moderate.

Common Causes For: U1857 U1857: “Module Communication Failure”

• Faulty wiring or connectors
• Failed control module
• Poor ground connections
• Corroded terminals
• Communication network issues (e.g., CAN bus problems)
• Software glitches or outdated firmware
• Interference from aftermarket devices
• Low battery voltage or power supply issues

Common misdiagnosis for U1859 U1859: “Module Communication Failure”

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

Common Troubleshooting Steps

The OBD-II code U1859 indicates a “Module Communication Failure,” which typically means that there is a problem with communication between various modules in the vehicle’s network. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Other Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, U-codes can be related to other issues that need to be addressed first.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the modules in question. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the CAN (Controller Area Network) bus wiring, as this is often where communication issues arise.
• Check Module Power and Ground:
• Ensure that the affected modules are receiving proper power and ground. Use a multimeter to check voltage and ground continuity.
• If a module is not powered correctly, it may not communicate with other modules.
• Test the Communication Network:
• Use a scan tool to monitor the communication between modules. Check if other modules are responding correctly.
• If possible, use an oscilloscope to check the CAN bus signals for proper voltage levels and signal integrity.
• Inspect for Short Circuits or Open Circuits:
• Check for any short circuits or open circuits in the wiring harness that could affect communication.
• Look for pinched wires or damaged insulation that could cause a short.
• Check for Module Failure:
• If the wiring and connections are good, the issue may be with one of the modules themselves. Consider testing or replacing the suspected module.
• If you have access to a known good module, you can swap it in to see if the problem resolves.
• Clear Codes and Test Drive:
• After performing any repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Monitor the vehicle’s performance and check for any other symptoms.
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to the U1859 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues that could help in diagnosing the problem.
• Professional Diagnosis:
• If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1859 code.