Lost Communication With Door Control Module A
Your vehicle's main computer lost its connection to the door control module, like a phone losing signal to a Bluetooth speaker. This prevents proper communication for power locks, windows, and door functions.
The ECU continuously monitors CAN bus communication signals from the door control module. It expects periodic heartbeat messages within a set timeout window. When no valid messages are received for the threshold duration, the ECU logs a lost communication fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Timeout | Messages received every 100-500ms | No valid message for >2 seconds |
| CAN Bus Voltage | 4.5-5.5V | <3V or >6V |
Code U0199 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, U0199 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.