U0199
Lost Communication With Door Control Module "A"
Get Your FREE AI Diagnostic Report
Enter your vehicle for a personalized diagnosis for code U0199
Code U0199 means that the vehicle's network has lost communication with Door Control Module A, which is typically the driver's side door module. Modern vehicles use dedicated electronic modules in each door to control power windows, door locks, mirror adjustment, courtesy lights, and sometimes seat memory functions. When this module stops communicating, all electronic features on that door may become inoperative.
The most common cause is broken wires inside the rubber flex boot that covers the wiring harness where it passes from the body into the door. Every time you open and close the door, these wires flex slightly, and after tens of thousands of cycles, individual conductors can break from metal fatigue. This is a well-known failure point across many vehicle makes and models. Moisture intrusion through worn door seals is another frequent culprit, causing corrosion at the module connector.
This code is generally low priority from a safety standpoint — the vehicle drives normally and all drivetrain and braking systems are unaffected. However, the loss of power window and door lock functionality can be inconvenient and may present a minor safety concern if the window cannot be closed during rain or the door cannot be locked. The repair often involves opening the door panel and inspecting or replacing the wiring in the door jamb boot, which is a moderately accessible DIY repair for those comfortable with automotive electrical work.
Severity
Symptoms
- •Driver's side power window does not operate
- •Door lock on the affected door unresponsive to button or remote
- •Side mirror adjustment not working from the driver's door switch
- •Interior courtesy light on the affected door does not turn on or off
- •Power seat controls on the affected door panel unresponsive
- •Window auto-up/auto-down feature disabled
Likely Causes
The wiring harness that passes through the door jamb boot flexes every time the door opens and closes. Over years of use, individual wires break from metal fatigue, interrupting communication with the door module.
A blown fuse, loose connector, or corroded ground point at the door module prevents it from operating and communicating. Verify battery voltage and ground continuity under load at the door module connector.
Moisture intrusion through worn door seals or clogged drain holes can corrode the door module's connector pins, creating high-resistance connections that disrupt CAN bus communication.
The door module's internal electronics can fail due to moisture exposure, temperature extremes, or age-related component fatigue, permanently preventing it from communicating on the network.
A fault on the CAN bus segment connecting the door module to the vehicle's network backbone prevents data exchange. This is more likely if multiple modules in the door are affected simultaneously.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Inspect and repair broken wires in the door jamb flex boot
- Clean corroded door module connector pins and apply dielectric grease
- Check and replace blown door module fuses
- Verify power and ground at the door module connector under load
- Replace the door control module