U1340 – Control Module Communication Error

The ODBII code U1340 indicates a communication error between control modules in a vehicle, suggesting that one or more modules are not properly communicating with each other.

The severity of ODBII code U1340: Control Module Communication Error is generally considered moderate to severe.

Common Causes For: 1. U1335: Module Communication Failure

• Faulty control module
• Poor or damaged wiring/connectors
• Corrupted software or firmware in the control module
• Low battery voltage or poor battery connections
• Faulty or malfunctioning sensors
• Interference from aftermarket devices
• Grounding issues
• Communication network issues (e.g., CAN bus problems)

Common misdiagnosis for 1. U1340: Control Module Communication Error

• Faulty control module
• Wiring issues or shorts
• Poor ground connections
• Corrupted software or firmware
• Faulty sensors
• Battery or charging system problems
• Intermittent connection issues
• Incorrectly installed aftermarket components

Common Troubleshooting Steps

The OBD-II code U1340 indicates a “Control Module Communication Error.” This code typically suggests 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 error.
• 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 ground connections, as poor grounding can lead to communication issues.
• Check for Short Circuits:
• Use a multimeter to check for short circuits in the wiring harnesses. A short can disrupt communication between modules.
• Verify Power Supply:
• Ensure that the control modules are receiving the proper voltage. Check the fuses related to the control modules and replace any that are blown.
• Inspect Control Modules:
• If possible, check the control modules themselves for any signs of damage or failure. This may involve removing the module and inspecting it for physical damage.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly.
• Check for Software Updates:
• Sometimes, control modules may require software updates to function correctly. Check with the manufacturer or a dealership to see if any updates are available.
• Reset the System:
• After performing inspections and repairs, clear the codes using the OBD-II scanner and see if the code returns. Sometimes, a simple reset can resolve temporary communication issues.
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to U1340.
• Seek Professional Help:
• If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics and diagnostics. By following these steps, you can systematically diagnose and potentially resolve the U1340 code.