U1320 – Lost Communication with the Body Control Module (BCM).

The ODBII code U1320 indicates a loss of communication between the vehicle’s control module and the Body Control Module (BCM), which may affect various electrical systems and functions.

The severity of ODBII code U1320 is generally considered moderate to high.

Common Causes For: U1319 Invalid or Missing Data for Vehicle Speed.

• Faulty Body Control Module (BCM)
• Damaged wiring or connectors
• Corroded terminals
• Blown fuses
• Poor ground connections
• Software issues or programming errors
• Intermittent electrical connections
• Malfunctioning sensors or components connected to the BCM

Common misdiagnosis for U1320 Lost Communication with the Body Control Module (BCM).

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Faulty or corroded connectors
• Issues with the Powertrain Control Module (PCM)
• Malfunctioning Instrument Cluster
• Battery or charging system problems
• Faulty fuses related to the BCM
• Software or programming issues in the BCM
• Grounding issues in the electrical system
• Other communication network failures (e.g., CAN bus issues)

Common Troubleshooting Steps

When dealing with OBD-II code U1320, which indicates “Lost Communication with the Body Control Module (BCM),” 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. Sometimes, other codes can provide context or indicate related issues.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors leading 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 pushed back.
• Check Power and Ground: **Power Supply: Verify that the BCM is receiving the correct voltage. Use a multimeter to check the power supply at the BCM connector.
• **Ground Connections: Ensure that the ground connections for the BCM are secure and free of corrosion.
• Inspect the BCM: **Physical Condition: Check the BCM for any signs of physical damage, such as cracks or burn marks.
• **Reprogramming: If the BCM has been replaced, it may need to be reprogrammed to the vehicle.
• Test Communication Lines: **CAN Bus: If your vehicle uses a CAN bus system, check the communication lines for continuity and proper signal. You may need an oscilloscope or a specialized scan tool to monitor the data lines.
• **Network Issues: Look for any other modules on the network that may be causing communication issues.
• Check for Intermittent Issues: **Temperature Sensitivity: Sometimes, issues can be temperature-related. Check if the problem occurs only under certain conditions (e.g., after the vehicle has been running for a while).
• **Vibration: Ensure that the BCM is securely mounted and not subject to excessive vibration.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the BCM and other modules. Reconnect and see if the code reappears.
• Scan Tool Functions: Use a professional scan tool to attempt to communicate with the BCM. If communication is not possible, it may indicate a fault in the BCM itself or the wiring.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the BCM or communication issues for your specific vehicle make and model. Manufacturers may have known fixes for common problems.
• Replace the BCM (if necessary): If all other troubleshooting steps fail and the BCM is determined to be faulty, replacement may be necessary. Ensure proper programming and configuration after replacement.Conclusion Always follow safety precautions when working on a vehicle’s electrical system. If you’re not comfortable performing these steps, or if the issue persists after your troubleshooting, it may be best to consult a professional mechanic or technician for further diagnosis and repair.