OBD-II Generic Error Code U0073: How to Fix It

Q: Can I drive my car with a U0073 error code?

It is not recommended. U0073 is a high-severity code indicating the main communication network between your car's control modules has failed or is unstable. This can disable safety systems like ABS, traction control, or airbags, and may also affect engine and transmission control. You should diagnose and repair this code before driving the vehicle regularly.

Q: What causes a U0073 code?

The most common causes are a damaged or shorted CAN bus wiring harness, corroded or loose connector terminals on a control module, a weak or failing battery causing low voltage on the bus, a faulty control module that is dragging down the bus, or a poor chassis or engine ground connection.

Q: Will a bad battery cause a U0073 code?

Yes, a weak or failing battery is one of the more common and overlooked triggers for U0073. The CAN bus requires stable voltage to operate correctly. When battery voltage drops below a threshold, modules may fail to communicate and drop off the bus, setting U0073. Always test your battery and charging system as part of diagnosing this code.

Q: How do I test the CAN bus with a multimeter?

With the ignition OFF and battery negative disconnected, measure resistance between pin 6 (CAN High) and pin 14 (CAN Low) of the OBD2 port. A healthy CAN bus reads approximately 60 ohms. A reading much higher than 60 ohms suggests an open circuit or broken wire, while a reading near 0 ohms indicates a short between the two CAN bus lines.

Q: Is U0073 the same as U0100 or other U-codes?

Not exactly. U0073 specifically means the communication bus itself (Bus A) is offline or inactive, while codes like U0100 mean a specific module (such as the ECM) lost communication. However, U0073 often triggers a cascade of other U-codes because when the bus goes down, all connected modules appear to lose communication. Fixing U0073 will typically resolve those secondary codes as well.

Abstract

Error code U0073 means your vehicle's Control Module Communication Bus A has gone offline, which is a serious fault in the CAN (Controller Area Network) bus system that allows your car's computers to talk to each other. When this bus shuts down, critical modules like the ECM, TCM, ABS, and airbag controllers may stop communicating, potentially disabling key vehicle functions. Because this is a high-severity code, you should avoid driving the vehicle until the root cause is identified and repaired.