Lost Communication with Door Module A
The U0199 code is set when the main control module (such as the BCM or gateway) stops receiving valid messages from the Door Control Module A (DCM-A) over the multiplexed network (CAN, LIN, or similar) for a manufacturer-defined period per SAE J2012. This module manages comfort functions for a specific door, including power windows, mirrors, locks, and puddle lights. The fault indicates a serial communication interruption, not necessarily damage to the final actuators.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Internal failure of the Door Control Module A, or loss of its power or ground
- Open, short-to-ground, short-to-voltage, or shorted-together wires in the communication bus (CAN-H, CAN-L, or LIN) branch to the DCM-A
- Corroded, bent, loose, or disconnected pins at the door module connector due to handling or moisture
- Blown fuse or excessive resistance in the power supply circuit to the DCM-A
- Out-of-specification terminating resistor on the network bus (e.g., abnormal CAN line values)
- Intermittent fault in the master network module (BCM/gateway) disrupting message routing to the door module
3. Symptoms You Will Notice
- Inoperative power windows, mirrors, door locks, or puddle lights on the affected door
- Door module not responding to switch inputs or remote commands
4. Step-by-Step Diagnosis
Scan for related communication codes and verify network integrity
Check power and ground at the DCM-A connector with a multimeter
Inspect the communication bus wiring for opens, shorts, or corrosion
Test the terminating resistor value on the network
Swap or test the DCM-A with a known-good module if possible
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle remains drivable, but comfort features on the affected door will not work. Have it diagnosed soon to prevent further issues.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the module, wiring, or connector needs replacement.