Vehicle Trouble Codes and Diagnostics

The "U0013 OBD-II: Medium Speed CAN Communication Bus (+) Low" code usually signals a communication issue within the vehicle's CAN (Controller Area Network) system, specifically with the medium-speed bus.

U0013 is a diagnostic trouble code (DTC) that highlights communication disruptions on the Medium-Speed CAN Bus. This bus is crucial for transmitting data between various control modules in the vehicle. The error indicates a low voltage reading on the Medium-Speed CAN Bus (+), suggesting that the voltage is lower than the expected level. The CAN Bus operates at different speeds-low, medium, and high-with the medium-speed bus handling communication for modules such as the transmission, airbags, and other control systems.

Symptoms:

Communication Failures, Dashboard Warning Lights, Erratic or Non-Responsive Vehicle Systems, Diagnostic Scan Results

Possible Causes of U0013 Code :

• Wiring Issues:

1. Short circuits, open circuits, or corroded connectors in the wiring harness.
2. Poor or loose connections between control modules.

• Faulty CAN Bus Module: One of the control modules connected to the medium-speed CAN bus may be malfunctioning or not transmitting/receiving signals correctly.
• Faulty Termination Resistor: CAN Bus networks require termination resistors at both ends to ensure proper signal reflection and communication. If these resistors are faulty or missing, the bus may show abnormal readings.
• Interference from Other Electronic Components: High electromagnetic interference from other vehicle systems or external sources could affect the communication on the bus.
• Software or Firmware Issues: In some cases, software bugs or issues within the control modules can lead to communication errors.
• Low Power Supply:If the vehicle's power supply is unstable or low, it can cause issues in the communication network.

How to Fix It?

Be sure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Common Diagnoses and Repairs:

• Inspect the CAN Bus Wiring: Check for any physical damage, loose connections, or corrosion in the wiring related to the CAN Bus.
• Replace Faulty Modules: If a specific control module is identified as the cause, it may need to be replaced or reprogrammed.
• Check Termination Resistors: Ensure that the termination resistors are in place and functioning correctly.
• Clear the Code and Test: After addressing the issue, clear the DTC and monitor the vehicle's performance to see if the problem recurs.