U1846 – BCM Communication Failure

The ODBII code U1846 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle’s network.

The severity of ODBII code U1846: “BCM Communication Failure” is generally considered moderate to severe.

Common Causes For: U1845 U1845: Instrument Cluster Communication Failure

• Faulty Body Control Module (BCM)
• Poor electrical connections or wiring issues
• Corroded connectors
• Malfunctioning CAN bus
• Software issues or programming errors
• Low battery voltage
• Faulty sensors or modules communicating with the BCM
• Intermittent faults in the communication network

Common misdiagnosis for U1846 U1846: “BCM Communication Failure”

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Defective or corroded connectors
• Malfunctioning power supply to the BCM
• Issues with other control modules (e.g., PCM, ECM)
• Software glitches or outdated firmware
• Battery or charging system problems
• Grounding issues in the electrical system

Common Troubleshooting Steps

The OBD-II code U1846 indicates a “BCM Communication Failure,” which typically means that the Body Control Module (BCM) is not communicating properly with other modules in the vehicle. 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 additional trouble codes. Other codes may provide more context or indicate related issues.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harnesses and connectors related to the BCM for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent or corroded.
• Test the BCM: **Power and Ground: Verify that the BCM is receiving proper power and ground. Use a multimeter to check voltage at the BCM connector.
• **Communication Lines: Check the communication lines (CAN bus) for continuity and proper voltage levels.
• Check for Short Circuits: Inspect the wiring for any short circuits to ground or to other wires that could affect communication.
• Inspect Other Modules: Since the BCM communicates with other modules, check if other modules (like the PCM, ABS, etc.) are functioning correctly. A failure in another module can sometimes cause communication issues.
• Perform a Network Test: Use a scan tool capable of performing a network test to check the communication between modules. This can help identify if the BCM is the issue or if another module is causing the problem.
• Update or Reprogram the BCM: If the BCM is functioning but still showing communication issues, it may need to be reprogrammed or updated with the latest software.
• Replace the BCM: If all other troubleshooting steps fail and the BCM is determined to be faulty, consider replacing it. Ensure that the replacement BCM is compatible with your vehicle.
• Clear Codes and Test Drive: After performing repairs or replacements, clear the codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult a Professional: If you are unable to resolve the issue, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model.Additional Tips: – Always refer to the vehicle’s service manual for specific diagnostic procedures and specifications. – Ensure that the vehicle’s battery is in good condition, as low voltage can cause communication issues. By following these steps, you should be able to diagnose and potentially resolve the U1846 BCM communication failure code.