U0216: Lost Communication With Door Switch B
What to do
The car drives normally. Expect an interior light that misbehaves, a wrong door-open warning, or an alarm that will not set — and see U0215 about batteries going flat, which is the consequence worth taking seriously.
You can usually identify the faulty door yourself in a couple of minutes, and it is worth doing before paying anyone. In a dark garage, open each door in turn and watch for the interior light, the chime, or the door showing on the display. The door that produces no reaction at all is the one at fault. If your car shows which door is open on its screen, that answers it directly — look for one permanently shown open, or one that never appears.
That is worth the effort because the repair usually means taking the door card off and replacing the latch, so identifying the wrong door costs hours.
What this code means
The second door switch has stopped being heard from. The framing — and the flat-battery consequence that makes this family worth reading — is at U0215.
What is worth adding here is how to find which door is at fault without a scan tool, because on a vehicle with four or more door switches the code's letter may not map obviously to a physical door.
The interior light is the instrument. Open each door in turn and watch whether the car responds — the light coming on, the display registering the door, the chime sounding. A door that opens with no reaction is the one reporting nothing, and that takes a minute in a dark garage. Doing it in reverse works too: with all doors shut, a car that still shows a door open is being told so by the faulty switch.
On vehicles that display which door is open on the instrument cluster or infotainment screen, the picture is given to you directly — a door shown permanently open, or one that never registers, names itself.
That identification matters because the repair is a door strip and a latch on most vehicles, so choosing the wrong door is several hours of labour for nothing.
Causes are as at U0215: water and salt at the latch, the door harness boot, and the connectors between.
Likely causes
Start here
- Water ingress into the module connector · moderate
- Corroded or loose connector · easy
- Broken wire in the door harness boot · moderate
Less common
- Blocked door drain letting water into the module · easy
- Damaged data bus wiring · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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