U0073

Control Module Communication Bus 'A' Off

Your car has a communication problem between control modules. One module may be faulty, or the wiring and connectors on the CAN network may be damaged or loose.

Severity4/5 High

Can I drive?⚠ With caution

You may be able to drive short distances, but the car can lose important functions like engine, transmission, ABS, or stability control communication. If warning lights are on or the vehicle runs poorly, have it checked soon and avoid long trips.

DIY

$20–$150

Shop

$150–$1,200

Difficulty

intermediate

What It Means

U0073 means the vehicle network has detected a problem on Communication Bus 'A', which is part of the CAN data network used by control modules to share information. The fault can be caused by a failed module, damaged wiring, corrosion, low system voltage, or a network short/open that prevents normal communication.

Symptoms

•Check engine light or multiple warning lights
•Intermittent no-start or hard start
•Loss of communication with one or more modules during scan
•Erratic gauges, warning lights, or dashboard messages
•ABS, traction control, or stability control faults
•Transmission shifting problems or limp mode
•Power steering, HVAC, or other electronic system issues
•Stored multiple communication-related trouble codes

Common Causes

1. Faulty control module on the CAN networkhigh

2. Corroded, loose, or damaged wiring and connectorshigh

3. Low battery voltage or charging system problemsmedium

4. Short to power, short to ground, or open circuit in CAN wiringmedium

5. Water intrusion in a module, connector, or junction pointmedium

6. Aftermarket device, alarm, remote start, or stereo interfering with network wiringlow

7. Blown fuse or poor power/ground supply to a control modulelow

Related Codes

U0001 U0100 U0121 U0140 U0155

FAQ

What does U0073 mean?

It means the vehicle has detected a fault in the CAN communication network on Bus 'A' or in a module connected to it.

Can a weak battery cause U0073?

Yes. Low voltage can disrupt module communication and set network fault codes.

Is U0073 always a bad control module?

No. Wiring, connectors, power supply, ground issues, and aftermarket electronics are often more common than a failed module.

Will clearing the code fix it?

Usually not. If the underlying network problem remains, the code will come back.