U0023 Trouble Codes and Diagnostics

The U0023 OBD-II code indicates a Low-Speed CAN Communication Bus (+) High issue. This code typically points to a communication fault within the vehicle’s CAN (Controller Area Network) system, specifically the Low-Speed CAN bus. The CAN bus is a network system that allows various control modules (e.g., engine control, transmission control, airbag system) in the vehicle to communicate with each other.

The "Low-Speed CAN Communication Bus (+) High" code is triggered when the voltage signal from the Low-Speed CAN bus (+) line is higher than expected by the vehicle’s computer. The vehicle’s control modules use this communication network to exchange data, and any issue in this communication can lead to malfunctions in various systems.

Symptoms:

Warning Lights, Communication Failures, Loss of Data Communication, Difficulties with Diagnostics

Possible Causes of U0023 Code :

• Wiring Issues: Damaged, corroded, or shorted wiring on the Low-Speed CAN bus can lead to irregular voltage levels.
• Faulty Control Module: A malfunctioning control module (such as an ABS or airbag module) might cause abnormal signal behavior.
• Loose or Corroded Connections: Poor electrical connections at connectors and terminals can lead to communication disruptions.
• Faulty CAN Bus Termination Resistor: Incorrect or failed termination resistors can create voltage irregularities on the network.
• Electrical Interference: Certain electrical components or aftermarket accessories may cause interference with the CAN bus communication.

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:

• Check the Wiring: Inspect the wiring and connections for damage, corrosion, or loose connections along the Low-Speed CAN bus.
• Scan for Other Codes: There may be additional trouble codes that could help pinpoint the specific module or area causing the issue.
• Test the Control Modules: Check the operation of the control modules linked to the Low-Speed CAN bus for faults.
• Inspect the CAN Bus Termination: Ensure that the CAN bus termination resistors are in place and functioning properly.
• Test Voltage Levels: Use a multimeter or oscilloscope to check for proper voltage levels on the Low-Speed CAN bus lines.