U0200 Lost Communication with Door Module B
The U0200 code indicates that the main control module (typically the BCM, PCM, or gateway) has lost serial communication over the vehicle network (CAN, LIN, or other protocol) with the 'Door Control Module B'. The 'B' designation usually refers to the passenger front door, left rear door, or a second door module depending on the manufacturer's architecture. This fault is set when the master module does not receive periodic status or heartbeat messages from the door module within a calibrated time.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Open circuit, short to ground, short to battery, or short between wires in the communication bus (CAN High/Low or LIN) to Door Module B
- Internal failure of Door Control Module B (hardware or software)
- Loss of power (B+) or ground to Door Control Module B (blown fuse, loose connector, damaged wiring)
- Damaged, corroded, or poorly seated connector at the door module
- Software configuration error or incompatible version after a reprogramming event
- Fault in the master module (BCM/Gateway) that manages the network
3. Symptoms You Will Notice
- Door functions (power locks, windows, mirrors) on the affected door may be inoperative
- Warning lights or messages on the dashboard related to door systems
4. Step-by-Step Diagnosis
Scan all modules to confirm U0200 and check for related communication codes
Inspect the communication bus wiring (CAN/LIN) to Door Module B for opens, shorts, or damage
Check power and ground circuits to Door Module B, including fuses and connectors
Test the door module by swapping with a known-good module if possible
Verify module software version and configuration; reprogram if necessary
If all else fails, suspect the master module (BCM/Gateway) and test its communication output
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but you may lose power functions on the affected door. Have it diagnosed soon to prevent further issues.
How much does it cost to fix?▼
The cost can range from $100 to $600 depending on the cause. A simple fuse or wiring repair may be under $200, while replacing a door module can be $300–$600 including labor.