U0004 – BMW DTC

BMW DTC U0004 – High Speed CAN Communication Bus (+) Low

DTC U0004 meaning on BMW

The DTC U0004 code on a BMW indicates a fault in the High Speed CAN Communication Bus (+) Low circuit. This means that there is a problem with the communication network that connects various control modules within the vehicle. The High Speed CAN bus is responsible for transmitting data between different systems such as the engine control module, transmission control module, and other electronic components.

BMW DTC U0004 symptoms

Symptoms of the DTC U0004 code on a BMW may include:

• Check Engine Light (CEL) illuminated on the dashboard
• Loss of communication with various control modules
• Erratic behavior of electronic systems
• Vehicle may go into limp mode

BMW DTC U0004 causes

Common causes of the DTC U0004 code on a BMW include:

• Faulty High Speed CAN Communication Bus wiring
• Loose or corroded connections in the CAN bus network
• Defective control module(s)
• Interference from aftermarket electronic devices

BMW DTC U0004 seriousness

The DTC U0004 code should be addressed promptly as it can lead to communication issues between critical vehicle systems. Ignoring this code may result in performance issues, safety concerns, and potential damage to other components.

How to diagnose DTC U0004 on BMW

To diagnose the DTC U0004 code on a BMW, a mechanic would typically perform the following steps:

1. Use a diagnostic scanner to retrieve the fault codes stored in the vehicle’s computer
2. Inspect the High Speed CAN Communication Bus wiring for any visible damage or corrosion
3. Check the connections and terminals in the CAN bus network for tightness and cleanliness
4. Test the control modules for proper functionality
5. Look for any aftermarket devices that may be causing interference

How to fix DTC U0004 on BMW

To fix the DTC U0004 code on a BMW, the following steps may be taken:

1. Repair or replace any damaged wiring in the High Speed CAN Communication Bus
2. Clean and secure all connections in the CAN bus network
3. Replace any faulty control modules identified during diagnosis
4. Remove any aftermarket electronic devices causing interference

How to erase DTC U0004 on BMW

After the underlying issue causing the DTC U0004 code has been resolved, the code can be cleared using a diagnostic scanner. This will reset the Check Engine Light and erase the fault code from the vehicle’s computer memory.

Recommended tools & DTC Scanners for BMW

Best Diagnostic App for modern BMWs: BimmerLink

Recommended Bluetooth adapter for Bimmerlink: OBDLink CX

Cable adapter for Bimmerlink: Enet Cable USB Type C

For older BMWs we recommend: Autel AutoLink AL319 (2024 version)

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

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