U1996 – Vehicle Communication Bus Malfunction

The ODBII code U1996 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U1996 is generally considered moderate.

Common Causes For: U1995 Invalid Data Received from Vehicle Control Module.

• Faulty wiring or connectors
• Malfunctioning control modules
• Poor ground connections
• Corroded or damaged pins in connectors
• Interference from aftermarket devices
• Software issues or bugs in the control modules
• Faulty or damaged communication bus (CAN bus) lines
• Low battery voltage or power supply issues

Common misdiagnosis for U1996 Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Bad Transmission Control Module (TCM)
• Defective Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Faulty sensors or actuators
• Battery or charging system problems
• Incorrectly installed aftermarket accessories
• Software or firmware issues in modules
• Corroded connectors or terminals
• Issues with the vehicle’s ground connections

Common Troubleshooting Steps

The OBD-II code U1996 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, which can affect the overall functionality of the vehicle’s systems. Here are some common troubleshooting steps to diagnose and resolve the U1996 code:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Addressing other codes may resolve the U1996 issue.
• Inspect the Wiring and Connectors: Examine the wiring and connectors related to the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the Engine Control Module (ECM), Transmission Control Module (TCM), and other related modules.
• Check the Fuses: Inspect the vehicle’s fuse box for any blown fuses that may affect the communication bus. Replace any blown fuses as necessary.
• Test the Modules: Verify that all modules on the communication bus are functioning correctly. This may involve checking for proper power and ground at each module.
• If a specific module is suspected to be faulty, it may need to be tested or replaced.
• Scan for Communication Issues: Use a professional-grade scan tool to check for communication between modules. Some tools can perform a network test to identify which module is not communicating properly.
• Inspect the CAN Bus: Check the CAN bus wiring for shorts, opens, or high resistance. Use a multimeter to measure the resistance on the bus.
• If you have access to an oscilloscope, you can check the signal waveform on the CAN bus to ensure it is within specifications.
• Look for Software Issues: Ensure that all modules have the latest software updates. Sometimes, a software glitch can cause communication issues.
• Reprogram or update the affected modules if necessary.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems, such as alarms, remote starters, or audio systems.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult a Professional: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics for further diagnosis.Conclusion Troubleshooting a U1996 code can be complex due to the nature of vehicle communication systems. Following these steps systematically can help identify and resolve the underlying issue. Always refer to the vehicle’s service manual for specific information related to the make and model you are working on.