U1625 – Vehicle Communication Bus Malfunction

The ODBII code U1625 indicates a malfunction in the vehicle communication bus, which affects the ability of various modules to communicate with each other.

The severity of ODBII code U1625 is moderate.

Common Causes For: U1622 U1622: Control Module Configuration Incompatibility

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corroded or damaged connectors
• Short circuits in the communication lines
• Open circuits in the communication lines
• Software issues or bugs in the control modules
• Interference from aftermarket devices or modifications
• Low battery voltage or power supply issues

Common misdiagnosis for U1625 U1625: “Vehicle Communication Bus Malfunction”

• Faulty ECM (Engine Control Module)
• Faulty BCM (Body Control Module)
• Wiring issues or shorts in the communication lines
• Faulty sensors or actuators
• Corrupted software or firmware in modules
• Battery or power supply issues
• Grounding problems
• Faulty diagnostic connector or interface
• Intermittent connection issues
• Other communication bus errors (e.g., CAN bus issues)

Common Troubleshooting Steps

The OBD-II code U1625 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 issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue.
• Inspect the Wiring and Connectors: Visually inspect the wiring and connectors associated with 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), Body Control Module (BCM), and any other modules that communicate over the bus.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the communication lines. Look for any short circuits or open circuits that could disrupt communication.
• Test the Modules: If possible, test the individual modules (like ECM, BCM, etc.) for proper operation. A malfunctioning module can cause communication issues.
• If you have access to a scan tool that can communicate with individual modules, check if they respond correctly.
• Inspect the CAN Bus: Use an oscilloscope or a CAN bus analyzer to check the signal integrity on the CAN bus. Look for any irregularities in the signal that could indicate a problem.
• Check the termination resistors (typically 120 ohms) at both ends of the CAN bus. If they are missing or faulty, it can lead to communication issues.
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the communication bus. This includes things like alarm systems, stereo systems, or other electronic devices.
• Update or Reprogram Modules: In some cases, a software update or reprogramming of the affected modules may resolve communication issues. Check with the manufacturer for any available updates.
• Clear Codes and Test Drive: After performing any repairs or adjustments, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U1625 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues that could help in troubleshooting.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with vehicle communication systems. By following these steps, you should be able to identify and resolve the underlying issue causing the U1625 code.