U0019 DTC: Medium Speed CAN Bus (+) Open

What Does U0019 Mean?

Diagnostic Trouble Code (DTC) U0019 indicates that the vehicle has detected an open circuit in the Medium-Speed CAN Bus High (CAN+) communication line. When the CAN High wire is broken or disconnected, electronic control modules cannot exchange data correctly, resulting in communication failures between multiple vehicle systems.

Symptoms

• Check Engine Light illuminated
• Multiple warning lights on the dashboard
• Loss of communication with one or more control modules
• Power windows, locks, or HVAC may not operate correctly
• Instrument cluster warning messages
• Scan tool communication errors
• Intermittent electrical malfunctions

Common Causes

• Broken CAN High (CAN+) wire
• Loose or disconnected connector
• Corroded terminals
• Damaged wiring harness
• Faulty Body Control Module (BCM)
• Internal failure of a control module
• Poor previous wiring repair

Typical Diagnostic Flow

Battery

│

▼

Scan Tool

│

▼

Inspect CAN High Wire

CAN High (+) ───────────────X CAN Low (-) ───────────────

Open Circuit Detected

▼

Repair Wiring or Replace Faulty Module

How to Diagnose U0019

• Scan every control module for communication faults.
• Inspect the CAN High wire for cuts or broken sections.
• Check connectors for loose or corroded terminals.
• Measure continuity of the CAN High circuit.
• Verify CAN bus voltage using a digital multimeter.
• Disconnect modules individually if necessary to isolate the fault.

Typical CAN Bus Values

• CAN High: approximately 2.5–3.5 V
• CAN Low: approximately 2.5–1.5 V
• Network resistance (Ignition OFF): approximately 60 Ω
• Actual specifications vary by manufacturer.

Estimated Repair Cost

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

Related DTCs

• U0018
• U0020
• U0100
• U0140
• U0155

Frequently Asked Questions

Can I drive with U0019?

The vehicle may still operate, but important electronic systems may lose communication. The fault should be repaired as soon as possible.

What is the most common cause of U0019?

The most common causes are an open CAN High wire, damaged connectors, or corrosion inside the communication network.

Will clearing the DTC solve the problem?

No. If the open circuit remains, the code will return after the next communication network self-test.