U2770 – Vehicle Communication Bus Malfunction

The ODBII code U2770 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 U2770 is moderate.

Common Causes For: U2769 Invalid Data Received from the Transmission Control Module (TCM)”.

• 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 poor ground connections

Common misdiagnosis for U2770 U2770: “Vehicle Communication Bus Malfunction”

• Faulty OBDII connector
• Bad ground connections
• Defective ECM (Engine Control Module)
• Malfunctioning BCM (Body Control Module)
• Wiring issues or shorts in the communication lines
• Faulty sensors or actuators
• Software glitches or outdated firmware
• Battery or power supply issues
• Corrupted data or communication protocols
• Interference from aftermarket devices or modifications

Common Troubleshooting Steps

The OBD-II code U2770 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 this 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 harnesses 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), Transmission Control Module (TCM), 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 (ECM, TCM, etc.) for proper operation. A malfunctioning module can cause communication issues.
• If you have access to a scan tool that can communicate with all modules, check if you can read data from each module.
• Inspect the CAN Bus: Check the CAN bus for proper voltage levels. The typical voltage levels should be around 2.5V to 2.8V when the bus is idle.
• Use an oscilloscope to check the signal integrity on the CAN bus lines (CAN High and CAN Low). Look for any irregularities in the waveform.
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the communication bus. This includes things like aftermarket radios, alarms, or other electronic devices.
• Update or Reprogram Modules: In some cases, a software update or reprogramming of the affected modules may be necessary. 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 U2770 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations for this issue.
• 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 your vehicle’s specific systems. By following these troubleshooting steps, you should be able to identify and resolve the underlying cause of the U2770 code.