U1634 – Vehicle Communication Bus Malfunction

The ODBII code U1634 indicates a malfunction in the vehicle communication bus, which affects the ability of various electronic control units (ECUs) to communicate with each other.

The severity of ODBII code U1634 is moderate.

Common Causes For: U1633 Invalid or Missing Data for Vehicle Speed.

• Faulty OBD-II connector
• Damaged wiring or connectors in the communication bus
• Malfunctioning control modules
• Poor ground connections
• Corroded or loose pins in the connectors
• Software issues or bugs in the control modules
• Interference from aftermarket devices
• Low battery voltage or power supply issues

Common misdiagnosis for U1634 U1634: “Vehicle Communication Bus Malfunction”

• Faulty OBDII connector
• Bad ground connections
• Defective ECM (Engine Control Module)
• Faulty wiring or harness issues
• Malfunctioning sensors
• Issues with the CAN bus system
• Problems with the body control module (BCM)
• Incorrectly installed aftermarket accessories
• Software glitches or updates needed
• Battery or power supply issues

Common Troubleshooting Steps

The OBD-II code U1634 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various control 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. Sometimes, other codes can provide context or lead to the root cause of the problem.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the communication bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the ECM (Engine Control Module), BCM (Body Control Module), and any other modules that communicate over the bus.
• Check for Short Circuits:
• Use a multimeter to check for short circuits in the communication lines. Ensure that the wires are not shorted to ground or to each other.
• Test the Modules:
• If possible, test the individual control modules for proper operation. This may involve using specialized diagnostic tools or software.
• Ensure that all modules are powered and grounded correctly.
• Inspect the CAN Bus:
• If your vehicle uses a CAN (Controller Area Network) bus, check the CAN bus lines for continuity and resistance. The typical resistance should be around 60 ohms when terminated correctly.
• Look for any interruptions or breaks in the bus lines.
• Check for Interference:
• Ensure that there are no aftermarket devices or modifications that could be interfering with the communication bus. This includes alarms, stereo systems, or other electronic devices.
• Battery and Ground Connections:
• Check the vehicle’s battery and ground connections. A weak battery or poor ground can cause communication issues.
• Update Software/Firmware:
• Check if there are any software updates available for the vehicle’s control modules. Sometimes, manufacturers release updates to fix communication issues.
• 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 dealership with advanced diagnostic tools to further investigate the problem. By following these steps, you should be able to identify and resolve the underlying issue causing the U1634 code.