CAN network

U0199 — Lost Communication with Door Control Module A

Severity: medium Safe to drive

What U0199 means

Other control units on the CAN bus have stopped receiving messages from door control module A, which is usually the driver door. Normally this module runs the window, locks, and mirrors and constantly exchanges data with the body control module and other units. When its messages disappear, U0199 is stored.

Symptoms

  • Power window on that door does not work
  • Door lock or central locking fails
  • Mirror controls are dead
  • Door switches do not respond
  • Several warning lamps may come on
  • Functions handled by the door module are unavailable

Possible causes

  1. Failed door control module
  2. Harness broken or chafed in the door jamb boot
  3. Water inside the door or on the module
  4. CAN bus wiring fault (open, short, chafed wires)
  5. Another faulty module loading the bus
  6. Corroded connector or terminals
  7. Power supply or ground fault at the module

How to diagnose

  1. Run a full-system scan and see which modules don't respond
  2. Look for other U-codes to tell a local fault from a bus-wide problem
  3. Inspect the harness in the door jamb and the module connectors for damage, moisture, and corrosion
  4. Check the module's power supply and ground
  5. Measure CAN bus voltage and resistance at the diagnostic connector (about 60 ohms total)
  6. Test the CAN wiring between the module and the nearest node for opens and shorts
  7. Unplug suspect modules one at a time, only following a documented procedure
  8. If the wiring is good, test or replace the door module

Common fixes

  • Repair or replace the damaged section of harness in the door jamb
  • Clean or replace corroded connectors and terminals
  • Fix the water leak and dry out the door
  • Restore power and ground to the module
  • Replace and program the door control module

Questions and answers

What does U0199 mean?

It means lost communication with door control module A, usually the driver door. Other modules are no longer receiving its data over the CAN bus.

Can I drive with a U0199 code?

Usually yes, because it does not affect how the car drives. The window, lock, or mirrors may not work, though, so get it repaired soon.

Why did U0199 appear after rain or a car wash?

Water has probably reached the module or its connector and caused a short or corrosion. Check the connectors and the harness in the door jamb.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.