Erratic central locking, windows or mirrors on a modern GTI usually traces to a door control module or the comfort control module (CCM) and their wiring.
Symptoms:
- One door won't lock/unlock, or a window/mirror is dead on one door.
- Or the whole car's comfort functions act up.
Diagnose:
- Scan the comfort/door modules on VCDS — it names the failed module or a broken wire.
- Check the door-loom wires in the rubber concertina boot between door and A-pillar first — they flex and break, and it's cheap.
The fix: repair the broken door-loom wires, or replace the door module / CCM (may need coding). Older Mk4-era cars use vacuum central locking — a pump and lines that leak, a different system.
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