What does U0073 mean?

The vehicle's main CAN bus has stopped communicating.

Why do I see many warning lights with U0073?

Modules cannot share data, so many systems report faults at once.

Network communication

U0073 — Control Module Communication Bus A Off

The CAN communication bus A has shut down, so control modules cannot exchange data. This often triggers many warning lights and other U codes at the same time.

Severity: Medium

Common causes

Short or open circuit in the CAN wiring
Faulty control module pulling down the bus
Low battery voltage or poor ground
Water damage or corroded connectors
Aftermarket device interfering with the bus

Symptoms

Many dashboard warning lights at once
Features or gauges not working
Engine or transmission not responding normally, possibly no start
Several U codes stored

How to check

Check battery voltage and the main ground points
Scan all modules to see which ones are not communicating
Check CAN wiring and connectors and the 60 ohm resistance across CAN high/low
Disconnect modules one at a time to find the one pulling the bus down

Can you keep driving?

Not recommended: critical systems may not communicate properly. Have the network diagnosed before normal driving.

Frequently asked questions

What does U0073 mean?: The vehicle's main CAN bus has stopped communicating.
Why do I see many warning lights with U0073?: Modules cannot share data, so many systems report faults at once.

General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.