U0023 DTC: Low Speed CAN Communication Bus (+) Shorted to Bus (-)

What Does U0023 Mean?

Diagnostic Trouble Code (DTC) U0023 indicates that the Low-Speed CAN Bus High (CAN+) communication wire is shorted to the CAN Low (CAN-) wire. When both communication circuits are electrically connected, network messages become corrupted or stop completely, causing communication failures between electronic control modules.

Symptoms

• Check Engine Light illuminated
• ABS, Airbag, or Traction Control warning lights
• Body control functions stop working
• Power windows, mirrors, or door locks malfunction
• HVAC system problems
• Instrument cluster warning messages
• Scan tool cannot communicate with some modules

Common Causes

• CAN High wire shorted to CAN Low wire
• Damaged or crushed wiring harness
• Melted insulation causing wire-to-wire contact
• Water intrusion inside connectors
• Corroded connector terminals
• Faulty BCM or another control module
• Incorrect aftermarket wiring modifications

Typical Diagnostic Flow

Battery

│

▼

Scan Tool

│

▼

Inspect Low-Speed CAN Wiring

CAN High (+)
──────────────

✖

CAN Low (-)
──────────────

Short Circuit Between CAN+ and CAN-

▼

Repair Wiring or Replace Faulty Module

How to Diagnose U0023

• Read all communication DTCs using a professional scan tool.
• Inspect the wiring harness for crushed or damaged wires.
• Disconnect modules individually to isolate the short circuit.
• Inspect connectors for moisture or corrosion.
• Measure CAN bus resistance with the ignition OFF.
• Verify CAN bus voltage using a digital multimeter.

Typical CAN Bus Values

• CAN High: approximately 2.5–3.5 V
• CAN Low: approximately 2.5–1.5 V
• Network resistance: approximately 60 Ω (Ignition OFF)
• Specifications may vary depending on the vehicle manufacturer.

Estimated Repair Cost

• CAN wiring repair: $80–300
• Connector replacement: $30–150
• Professional CAN diagnosis: $100–250
• Control module replacement: $250–1,000+

Related DTCs

• U0021
• U0022
• U0024
• U0100
• U0140

Frequently Asked Questions

Can I drive with U0023?

The vehicle may still run, but communication between electronic modules may be unreliable. Important systems such as ABS, airbags, and body electronics may not function correctly.

What usually causes U0023?

The most common causes are damaged wiring, melted insulation allowing CAN High and CAN Low wires to touch, water intrusion, or an internally failed control module.

Will clearing the code permanently fix U0023?

No. The DTC will return until the short circuit between the CAN communication wires has been repaired.