U1852 – Lost Communication with Body Control Module (BCM) – Bus Off.

The ODBII code U1852 indicates that there is a loss of communication with the Body Control Module (BCM) due to a “Bus Off” condition, meaning the BCM is not responding on the communication network, likely due to a fault in the wiring, module, or network.

The severity of ODBII code U1852 is moderate to severe.

Common Causes For: U1851 Lost Communication with the Instrument Panel Cluster (IPC) Control Module.

• Faulty Body Control Module (BCM)
• Damaged wiring or connectors in the communication circuit
• Short circuit or open circuit in the CAN bus
• Faulty or corroded ground connections
• Malfunctioning or damaged CAN bus transceiver
• Issues with other modules on the CAN bus
• Software or firmware issues in the BCM
• Low battery voltage or power supply issues

Common misdiagnosis for U1852 Lost Communication with Body Control Module (BCM) – Bus Off.

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Faulty or corroded connectors
• Issues with the power supply to the BCM
• Faulty Instrument Cluster
• Problems with the Engine Control Module (ECM)
• Malfunctioning CAN bus system
• Software or firmware issues in the BCM
• Other module communication failures
• Grounding issues in the electrical system

Common Troubleshooting Steps

When dealing with the OBD-II code U1852, which indicates “Lost Communication with Body Control Module (BCM) – Bus Off,” there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:

• 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 harness 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, corroded, or damaged.
• Check 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.
• **Functionality: If possible, test the BCM in another vehicle or replace it with a known good unit to see if the problem persists.
• Inspect the CAN Bus: **Bus Communication: The BCM communicates over the Controller Area Network (CAN) bus. Check for continuity and proper resistance in the CAN bus wiring.
• **Termination Resistors: Ensure that the CAN bus has the correct termination resistors in place. A missing or faulty resistor can cause communication issues.
• Check for Short Circuits: Use a multimeter to check for short circuits in the wiring harness that could affect communication between the BCM and other modules.
• Scan for Module Communication: Use a scan tool to check if other modules on the CAN bus are communicating properly. If other modules are also showing communication issues, the problem may be with the bus itself rather than the BCM.
• Inspect for Environmental Factors: Check for any environmental factors that could affect the BCM, such as water intrusion or extreme temperatures.
• Reset the System: Clear the trouble codes using the OBD-II scanner and see if the code returns. Sometimes, a temporary glitch can cause communication issues.
• Update Software/Firmware: If applicable, check if there are any software updates available for the BCM or the vehicle’s control modules. Sometimes, manufacturers release updates to fix communication issues.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have documented common issues and fixes for the U1852 code.1
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing BCM and communication issues. By following these steps, you should be able to identify the root cause of the U1852 code and take appropriate action to resolve the issue.