U1842 – Module Communication Failure

The ODBII code U1842 indicates a “Module Communication Failure,” meaning there is a problem with communication between the vehicle’s control modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1842 is moderate.

Common Causes For: U1841 U1841: Instrument Cluster Communication Fault

• Faulty wiring or connectors
• Failed control module
• Poor ground connections
• Corrupted software or firmware
• Intermittent electrical issues
• Low battery voltage
• Communication network issues (e.g., CAN bus problems)
• Damaged or corroded pins in connectors
• Incompatible or missing modules
• Electrical interference from other components

Common misdiagnosis for U1842 U1842: “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 U1842 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, other codes can provide additional context for the U1842 code.
• 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 modules are receiving proper power and ground. Use a multimeter to check voltage and ground continuity at the module connectors.
• If there is no power or ground, trace the wiring back to the source to identify any breaks or shorts.
• Test Communication Lines:
• Use a scan tool to check the communication lines (CAN bus, LIN bus, etc.) for proper operation. You may need to use an oscilloscope to analyze the signals on the communication lines.
• Look for any interruptions or noise in the communication signals.
• Inspect Modules:
• If possible, test the affected module(s) by swapping them with known good modules to see if the problem persists.
• Check for any software updates or reprogramming that may be required for the modules.
• Check for Intermittent Issues:
• Sometimes, communication failures can be intermittent. Pay attention to when the code appears (e.g., during specific driving conditions) and try to replicate the issue.
• Clear Codes and Test Drive:
• After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the U1842 code returns.
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures related to the U1842 code and the modules involved.
• 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 U1842 code.