U0026 DTC: Low Speed CAN Communication Bus (-) Low

What Does U0026 Mean?

Diagnostic Trouble Code (DTC) U0026 indicates that the Low-Speed CAN Bus Low (CAN-) circuit voltage is below the expected operating range. This abnormal voltage can interrupt communication between electronic control modules, leading to network errors and malfunctioning vehicle systems.

Symptoms

• Check Engine Light illuminated
• ABS, Airbag, or Stability Control warning lights
• Body control system malfunctions
• Power windows, mirrors, or door locks may stop working
• HVAC system problems
• Communication errors with a scan tool
• Multiple communication DTCs stored

Common Causes

• CAN Low wire shorted to ground
• Damaged or pinched wiring harness
• Loose or corroded connectors
• Water intrusion into CAN connectors
• Faulty CAN transceiver inside a control module
• Poor ground connection
• Improper aftermarket electrical modifications

Typical Diagnostic Flow

Battery

│

▼

Scan All Modules

│

▼

Check CAN Low Voltage

Normal CAN Low (-) ────────────── U0026: ▼ ────────────── Low Voltage

CAN- Voltage Too Low

▼

Repair Wiring or Replace Faulty Module

How to Diagnose U0026

• Read all stored communication DTCs.
• Measure CAN Low voltage with a digital multimeter.
• Inspect the CAN wiring harness for damage or contact with ground.
• Check connectors for corrosion or moisture.
• Inspect ground circuits for excessive resistance.
• Disconnect modules one at a time 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: approximately 60 Ω (Ignition OFF)
• Actual values vary by manufacturer.

Estimated Repair Cost

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

Related DTCs

• U0024
• U0025
• U0027
• U0100
• U0140

Frequently Asked Questions

Can I drive with U0026?

The vehicle may continue to operate, but communication between electronic modules can become unstable, affecting safety and convenience systems.

What is the most common cause of U0026?

The most common causes are a CAN Low wire shorted to ground, damaged wiring, poor ground connections, corroded connectors, or a faulty control module.

Will clearing the DTC permanently fix U0026?

No. The fault code will return until the low-voltage condition on the CAN Low circuit is repaired.