U1700 – Control Module Communication Fault

The ODBII code U1700 indicates a “Control Module Communication Fault,” which means there is a problem with the communication between various control modules in the vehicle’s network.

The severity of ODBII code U1700 is generally considered moderate to severe.

Common Causes For: U1699 Manufacturer Specific Communication Bus Fault.

• Faulty control module
• Poor electrical connections
• Damaged wiring harness
• Corroded connectors
• Software issues or bugs
• Faulty CAN bus communication
• Low battery voltage
• Interference from aftermarket devices
• Grounding issues
• Faulty sensors or actuators

Common misdiagnosis for U1700 U1700: “Control Module Communication Fault”

• Faulty control module
• Wiring issues or damaged connectors
• Corrupted software or firmware in the control module
• Battery or power supply problems
• Grounding issues
• Faulty sensors or actuators
• Communication network problems (e.g., CAN bus issues)
• Intermittent electrical connections

Common Troubleshooting Steps

The OBD-II code U1700 indicates a “Control Module Communication Fault.” This code typically means that there is a problem with communication between the vehicle’s control modules. 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 communication fault.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the control modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the wiring harnesses that connect the affected modules.
• Check Power and Ground:
• Ensure that the control modules have proper power and ground connections. Use a multimeter to check voltage and ground continuity.
• If a module is not receiving power or ground, trace the circuit back to find the issue.
• Test Control Modules:
• If possible, test the affected control modules individually. This may involve swapping with a known good module or using a diagnostic tool to check module functionality.
• Ensure that the modules are compatible with your vehicle.
• Inspect the CAN Bus:
• The Controller Area Network (CAN) bus is responsible for communication between modules. Check for shorts, opens, or faults in the CAN bus wiring.
• Use an oscilloscope or CAN bus diagnostic tool to monitor the bus for proper signals.
• Check for Software Updates:
• Sometimes, communication issues can be resolved with a software update. Check with the manufacturer for any available updates for the control modules.
• Clear Codes and Test Drive:
• After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Monitor the vehicle’s performance and check for any symptoms that may indicate ongoing issues.
• Consult Technical Service Bulletins (TSBs):
• Look for any TSBs related to the U1700 code for your specific vehicle make and model. Manufacturers may have documented common issues and fixes.
• 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 can systematically identify and resolve the underlying cause of the U1700 code.