OBD-II Generic Error Code U0284: How to Fix It

Q: Can I drive my car with error code U0284?

In many cases the vehicle will still start and drive with U0284 active, but you may experience malfunctions in electrical accessories controlled by BCM-B such as power windows, door locks, interior lighting, or wipers. It is best to address the fault promptly, as a module that has dropped off the CAN network can sometimes prevent other safety-related systems from operating correctly. Avoid long trips until the issue is diagnosed.

Q: What is Body Control Module B and what does it control?

Body Control Module B (BCM-B) is a secondary or auxiliary body control module found on some vehicles that have enough electrical complexity to require more than one BCM. Depending on the vehicle, it may control functions such as interior lighting zones, power seat memory, door lock and unlock functions, accessory power outlets, or rear climate controls. The exact functions vary by make and model.

Q: Will a bad battery really cause a U0284 code?

Yes — a weak, failing, or heavily discharged battery is one of the most common triggers for U-series communication codes including U0284. When battery voltage drops below a critical threshold, modules can lose power and drop off the CAN bus network, which the other modules interpret as a communication loss fault. Always check battery health first before assuming a module has failed.

Q: How much does it cost to fix error code U0284 at a dealership?

Costs vary significantly depending on the root cause. If it is a simple fix like a blown fuse, corroded connector, or bad battery, you may spend $20–$150. If BCM-B needs to be replaced and programmed, parts and labor can range from $300 to over $1,000 depending on the vehicle make and model. Diagnostic labor alone at a dealership typically runs $100–$200 for the first hour.

Q: Can I fix U0284 by just clearing the code with a scanner?

Clearing the code without repairing the underlying cause will only result in the code returning, usually within the same drive cycle. U0284 is a communication fault that must be physically diagnosed and repaired. Simply erasing it with a scan tool does not fix the wiring, connector, ground, or module issue causing the communication loss.

Abstract

Error code U0284 indicates that your vehicle's main computer (the PCM or another control module) has lost communication with Body Control Module B (BCM-B), which manages various electrical systems like lighting, windows, door locks, and accessories. This is a network communication fault on the CAN bus — the internal wiring network that allows all your vehicle's computers to talk to each other. While the vehicle may still be drivable, unresolved communication faults can cause electrical accessories to malfunction and may trigger additional error codes over time.