U1823 – Module Communication Failure

The ODBII code U1823 indicates a “Module Communication Failure,” meaning there is a problem with communication between the vehicle’s control modules, often due to a wiring issue, a faulty module, or a network problem.

The severity of ODBII code U1823 is moderate.

Common Causes For: U1821 U1821: “Network Communication Line Fault”

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Corrupted software or firmware in the module
• Poor ground connections
• Intermittent communication issues
• Electrical interference
• Low battery voltage or power supply issues
• Damaged or corroded pins in connectors

Common misdiagnosis for U1823 U1823: “Module Communication Failure”

• 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

Common Troubleshooting Steps

The OBD-II code U1823 indicates a “Module Communication Failure,” which typically means that there is a problem with communication between the vehicle’s control modules. 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, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the affected modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the wiring harnesses that connect the modules, as these can be prone to wear and tear.
• Check Power and Ground:
• Ensure that the affected module(s) are receiving proper power and ground. Use a multimeter to check voltage and ground continuity.
• If the module is not receiving power, trace the wiring back to the fuse box and check for blown fuses or damaged wiring.
• Test the Affected Module:
• If possible, test the affected module to see if it is functioning correctly. This may involve bench testing or swapping with a known good module.
• If the module is faulty, it may need to be replaced.
• Check for Communication Issues:
• Use a scan tool to check if the affected module is communicating with other modules. If it is not, there may be a communication bus issue.
• Inspect the CAN (Controller Area Network) bus wiring for shorts, opens, or interference.
• Inspect for Interference:
• Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication network, such as alarms, remote starters, or audio systems.
• 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.
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures related to the U1823 code and the affected modules.
• Professional Diagnosis:
• If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues. By following these steps, you should be able to identify and resolve the underlying cause of the U1823 code.