U0035 DTC: Vehicle Communication Bus A (+) Shorted to Ground

What Does U0035 Mean?

Diagnostic Trouble Code (DTC) U0035 indicates that the Vehicle Communication Bus A CAN High (CAN+) circuit has been shorted directly to ground. This causes the CAN High voltage to drop below its normal operating range, interrupting communication between electronic control modules and leading to multiple network-related faults.

Symptoms

• Check Engine Light illuminated
• ABS, Airbag, or Stability Control warning lights
• Multiple communication DTCs stored
• Loss of communication with one or more control modules
• Power windows, mirrors, door locks, or HVAC may stop working
• Instrument cluster warning messages
• Diagnostic scan tool cannot communicate with some modules

Common Causes

• CAN High wire shorted to ground
• Damaged or pinched wiring harness
• Worn insulation contacting the chassis
• Water intrusion inside CAN connectors
• Loose or corroded connector terminals
• Faulty control module internally grounding the CAN High circuit
• Improper aftermarket electrical modifications

Typical Diagnostic Flow

Battery

│

▼

Professional Scan Tool

│

▼

Inspect Bus A CAN High

CAN High (+) ────────────── │ ▼ GROUND CAN Low (-) ──────────────

CAN High Shorted to Ground

▼

Repair Wiring or Replace Faulty Module

How to Diagnose U0035

• Read all stored communication DTCs using a professional scan tool.
• Inspect the CAN High wiring for contact with the chassis or damaged insulation.
• Check connectors for corrosion, moisture, or loose terminals.
• Measure CAN bus resistance with the ignition OFF (approximately 60 Ω).
• Measure CAN High voltage using a digital multimeter.
• Disconnect control modules individually to isolate the source of the short.

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 specifications vary by vehicle manufacturer.

Estimated Repair Cost

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

Related DTCs

• U0033
• U0034
• U0036
• U0100
• U0140

Frequently Asked Questions

Can I drive with U0035?

The vehicle may still operate, but communication failures can affect safety, body, and comfort systems. The fault should be repaired as soon as possible.

What is the most common cause of U0035?

The most common causes are damaged CAN High wiring touching ground, water-damaged connectors, corrosion, or a defective control module internally shorting the CAN High circuit.

Will clearing the DTC permanently fix U0035?

No. Clearing the code only removes it temporarily. The DTC will return until the short-to-ground condition on the CAN High circuit has been repaired.