U1636 – BCM Communication Failure

The ODBII code U1636 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle’s network.

The severity of ODBII code U1636: “BCM Communication Failure” is generally considered moderate to severe.

Common Causes For: U1635 CAN Communication Bus Fault.

• Faulty Body Control Module (BCM)
• Poor electrical connections or wiring issues
• Corroded or damaged connectors
• Malfunctioning sensors or actuators
• Software or firmware issues in the BCM
• Low battery voltage or power supply issues
• Interference from aftermarket accessories
• Faulty communication lines (CAN bus issues)

Common misdiagnosis for U1636 U1636: “BCM Communication Failure”

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Defective or corroded connectors
• Malfunctioning other control modules (e.g., PCM, ECM)
• Power supply issues to the BCM
• Software or firmware issues in the BCM
• Grounding problems
• Faulty sensors or actuators related to the BCM
• Intermittent communication issues due to environmental factors
• Battery or charging system problems

Common Troubleshooting Steps

The OBD-II code U1636 indicates a “BCM Communication Failure,” which typically means that there is a problem with the communication between the Body Control Module (BCM) and other modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide additional context for the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the BCM. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check Power Supply: Ensure that the BCM is receiving the correct voltage. Use a multimeter to check the power supply to the BCM.
• Verify that the fuses related to the BCM and communication circuits are intact.
• Test the BCM: If possible, perform a functional test of the BCM using a scan tool. Check for any abnormal readings or failures.
• If the BCM is suspected to be faulty, consider replacing it or reprogramming it if necessary.
• Inspect Other Modules: Check the communication between the BCM and other modules (e.g., ECM, ABS, etc.). If other modules are malfunctioning, they may affect the BCM’s ability to communicate.
• Look for any signs of failure in other modules that could be causing the communication issue.
• Check for Short Circuits: Use a multimeter to check for short circuits in the wiring harness connected to the BCM. A short can disrupt communication.
• Perform a Network Test: If your scan tool supports it, perform a network test to check for communication between all modules on the vehicle’s network.
• Look for any modules that are not responding or are showing communication errors.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner.
• Take the vehicle for a test drive to see if the code reappears.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U1636 code for your specific vehicle make and model. Manufacturers may have specific fixes or updates for known issues.
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1636 code.