OBD-II Network Error Code U0004: How to Fix It

Q: What causes OBD-II error code U0004?

U0004 is caused by a short circuit in the high-speed CAN bus wiring, typically from damaged wires touching ground, corrosion in connectors, or water intrusion into electrical components.

Q: Can I drive with error code U0004?

You should not drive with U0004 as it indicates communication failure between critical vehicle systems. This can affect engine management, transmission, ABS, and other safety systems.

Q: How much does it cost to fix error code U0004?

Repair costs range from $150-$800 depending on the location and extent of wiring damage. Simple connector cleaning may cost $150-$300, while complete harness replacement can cost $500-$800 plus labor.

Q: Will U0004 clear itself?

No, U0004 will not clear itself as it indicates a physical wiring problem that requires repair. The code will persist until the short circuit is located and fixed.

Q: What other codes appear with U0004?

U0004 often appears with other U-codes like U0100, U0101, or U0155, which indicate lost communication with specific modules affected by the CAN bus short circuit.

Abstract

Error code U0004 indicates a short circuit in your vehicle's high-speed CAN (Controller Area Network) bus system, specifically where the circuit is shorted to ground or another bus line. This communication error can cause multiple vehicle systems to malfunction and should be addressed immediately.