U0199–U0205 Lost Communication With Door Control Module A
This module has stopped talking on the car's data network, so nothing else can hear it.
Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
U0199 | Lost Communication With Door Control Module A | Investigate soon |
U0203 | Lost Communication With Door Control Module 'E' | Investigate soon |
U0204 | Lost Communication With Door Control Module 'F' | Investigate soon |
U0205 | Lost Communication With Door Control Module 'G' | Investigate soon |
The definition
U0199: Lost Communication With Door Control Module A.
U0199 is a network code (communication between control modules), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.
What to check first
Cheapest and fastest checks first:
- Check power and earth at the module first - a module with no supply cannot answer.
- Check the two data-bus wires for continuity and for a short between them.
- Scan the other modules: if several report the same module missing, the fault is at that module rather than on the bus.
What actually causes this on a VAG
On VAG models with the full comfort system, the doors - certainly the front pair, and on better-equipped cars the rear ones too - each have a small control module handling the window, mirror, lock and door lighting for that door, and they talk to the rest of the car over the comfort data network. On simpler cars a single central comfort module does that job instead. This code means one of those door modules, module 'A' being the driver's door, has stopped communicating. You will usually see it as one door going dead or half-dead: window and mirror not working, central locking behaving oddly on that door, mirrors not folding, or the interior light not responding when that door opens. An intermittent dropout can also confuse the alarm and the locking, so it is worth fixing rather than living with.
Most likely causes, in order
- Broken wires in the rubber boot between door and A-pillar. The classic, and by a wide margin the most common cause on these cars. The wires inside that flexible concertina bend every single time the door opens, and eventually the copper fractures inside insulation that still looks perfect. The fault is typically intermittent and changes as the door moves. Peel the boot back and flex the loom by hand while watching for the functions to come and go - that alone usually finds it, and it costs nothing.
- Water inside the door. Blocked drain holes at the bottom of the door, or a plastic vapour barrier not properly resealed after earlier work, let water sit against the module and its connectors. Take the door card off and look for water marks, soggy sound-deadening and corroded pins. Clear the drains and reseal the barrier as part of the repair, or it will simply happen again.
- A voltage event rather than a genuine failure. A flat battery, a jump start or a battery replacement can knock modules off the network momentarily and leave stored codes behind. If everything works normally now, clear the fault, use the car for a few days and only chase it if it comes back.
- Lost supply, or the door module itself. Check the module's fuse and the condition of its main connector first - both are quick and cheap. The module itself failing is the last conclusion, not the first, because the door loom and water ingress account for most cases and cost a fraction as much to put right.
Worth knowing: Broken wires in the door boot are repairable - you do not need a new door harness or a new module. An auto electrician can identify the fractured cores and splice them properly for far less than the parts people are often quoted for this code. One more thing that saves money: after any battery disconnect or door repair, VAG windows commonly need re-initialising before one-touch and anti-pinch work again, usually by closing the window fully and holding the switch in the closed position for a few seconds, then repeating with the window fully open. People replace perfectly good motors because the window will only move in short nudges, when all it needed was that procedure.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
$249 once. No subscription, unlimited cars. Windows 10/11.
See VAGPULSE — $249 Look up another codeSoftware downloads instantly · cable ships September 30 · cable guarantee — refund if it won't connect
Prefer to work on your phone? The VAGPULSE Android app is a free download and its demo mode runs against a sample car with no hardware at all, so you can see exactly what it reads before spending anything. Reading your car with it needs the VAGPULSE cable, which comes with the licence.
Common questions
What does U0199 mean?
U0199 means Lost Communication With Door Control Module A. This module has stopped talking on the car's data network, so nothing else can hear it.
Can I drive with U0199?
The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.