U0019: Medium Speed CAN Communication Bus (+) High

CAN-High on the medium-speed bus is shorted to battery voltage. The bus is non-functional and all comfort modules drop offline.

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

Most likely causes

• CAN-High shorted to battery
• Gateway module routing CAN messages incorrectly
• CAN terminating resistor (120 Ω) drifted out of spec

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and terminals, and read the codes from all control modules with a multi-system scanner
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Identify which control module is not responding and check its fuses, power supply, and grounds
4. Disconnect add-on accessories, such as alarms or trackers, and read the codes again
5. Inspect the network connectors for moisture or bent pins
6. Measure the network's resistance and signal using the manufacturer's wiring diagram

Good to know

• Repair difficulty: hard

What each character of U0019 means

• U: Communication network
• 0: Generic code: same on every make
• 0: Subsystem depends on the code range
• 19: Specific fault in that system

Frequently asked questions

Can I keep driving with code U0019?

It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.

What causes code U0019?

The most common causes are: cAN-High shorted to battery; gateway module routing CAN messages incorrectly; cAN terminating resistor (120 Ω) drifted out of spec.

Sources

• en.wikipedia.org: CAN bus

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.