U1117 – Control Module Communication Bus Off.

The ODBII code U1117 indicates a communication issue where a control module is not responding or is offline on the communication bus, potentially due to a fault in the module or wiring.

The severity of ODBII code U1117 is typically considered moderate to severe.

Common Causes For: U1116 SCP (J1850) Invalid or Missing Data for Electrical Energy Management

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Communication bus short circuit
• Open circuit in the communication bus
• Intermittent electrical connections
• Faulty or incompatible aftermarket components
• Software or firmware issues in the control module

Common misdiagnosis for U1117 Control Module Communication Bus Off.

• Faulty control module
• Wiring issues
• Poor ground connections
• Faulty sensors
• Battery or charging system problems
• Corrupted software or firmware
• Communication network issues
• Intermittent connection problems

Common Troubleshooting Steps

The OBD-II code U1117 indicates a communication issue between the control modules in a vehicle, specifically that a control module is “bus off.” This typically means that the module is unable to communicate on the CAN (Controller Area Network) bus due to a fault. 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. Other codes can provide context and help identify the root cause of the communication issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors associated with the control module that is reporting the U1117 code. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the CAN bus wiring, which typically consists of a twisted pair of wires.
• Test the Control Module: If possible, test the control module that is reporting the U1117 code. This may involve checking for proper power and ground at the module.
• If the module is removable, consider swapping it with a known good module to see if the problem persists.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for short circuits or open circuits in the CAN bus wiring. Ensure that the resistance between the CAN High and CAN Low wires is within specifications.
• Inspect Other Modules: Check other control modules on the CAN bus for faults. A malfunctioning module can cause communication issues for the entire bus.
• Disconnect other modules one at a time to see if the U1117 code clears, indicating that one of the other modules may be causing the issue.
• Check for Interference: Look for any aftermarket devices or modifications that may be interfering with the CAN bus communication. This includes things like alarm systems, stereo systems, or other electronic accessories.
• Update or Reprogram Modules: In some cases, a software update or reprogramming of the control module may be necessary. Check with the manufacturer for any available updates.
• Scan Tool Communication: Ensure that your OBD-II scanner is functioning properly and can communicate with all modules. Sometimes, a faulty scanner can give misleading information.
• Battery and Ground Connections: Check the vehicle’s battery and ground connections. A weak battery or poor ground can lead to communication issues.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to the U1117 code.1
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you should be able to identify and resolve the underlying issue causing the U1117 code.