U0141: Lost Communication With Body Control Module A
What to do
Expect a whole group of things in one part of the car to have stopped at once — lights, locks, windows, wipers, interior lighting.
Modern cars split their electrics between several computers, each looking after one area. This code means one of them has stopped talking to the rest of the car, so everything it controls has gone quiet together.
The good news is where that points. Each of these computers usually sits next to its own fuse box, so one blown fuse or one failed relay can take out the computer and its whole area in one go. That is far commoner than a failed module and enormously cheaper. Ask for the fuses and relays nearest the dead area to be checked first.
If a fuse blows again straight away, that is information rather than an annoyance — something in that area is shorting, and it needs finding. Never let anyone fit a bigger fuse to stop it blowing. That is how a wiring fault turns into a fire.
And check your carpets. These computers live inside the cabin, so a blocked drain, a leaking heater or a perished windscreen seal puts water straight onto them — damp carpets and odd electrics are usually the same fault.
Before driving at night, check your lights, indicators and brake lights are all working.
What this code means
A body control module has stopped being heard from. The general reasoning is at U0100, U0140 covers the unlettered entry, and U0443 explains why these modules are lettered at all — they are zones rather than ranks, and roughly where each one lives determines how it fails.
Silence has one property bad data does not, and it is the most useful thing on this page: a zone module that goes quiet takes everything at that location with it, all at once.
Which turns the diagnosis into a question about power rather than about data. Each zone module normally sits beside its own fuse box — that is the point of putting it there, so that the fuses feeding the lamps, motors and heaters it operates are local too. So one failed supply can take out the module and its whole zone in a single stroke.
That gives a free first check that is right far more often than it deserves to be: the fuses and relays in the box nearest the dead area. A whole corner of the vehicle going dark at once is much likelier to be a supply than a module, and a module is expensive while a fuse is not.
The second check is what the fuse blew for. A fuse that fails again immediately is reporting a short somewhere in the zone — a chafed wire in a door, a lamp holder full of water, a trapped harness — and fitting a larger fuse in response is how a wiring fault becomes a fire.
And the U0140 argument applies unchanged: check the carpets. These modules sit in the cabin, in the path of a blocked bulkhead drain, a leaking heater matrix or a perished screen seal, and damp carpets with strange electrics are one fault far more often than two.
Likely causes
Start here
- Blown fuse or failed supply · easy
- Water ingress into module · moderate
- Failed power or earth supply to the module · moderate
- Corroded or loose connector · easy
Less common
- Damaged data bus wiring · moderate
- Faulty body control module · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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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