OBD-II code family
Lost Communication with Body Control Module (U0142–U0145)
4 codes describing the same fault on 4 enumerated slots. The letter is the index your manufacturer assigned — it is not a physical difference, and it does not carry across makes.
What these codes mean
The body control module runs the parts of a vehicle that are not the engine or the transmission: exterior and interior lighting, wipers, power windows and locks, the horn, chimes, interior illumination, and on many vehicles part of the anti-theft and keyless entry system. It is also one of the busiest talkers on the network, which is why its silence is noticed quickly and by many other modules.
When this family of codes sets, another module has stopped receiving the body control module's messages. The symptoms are usually obvious and scattered across unrelated systems at once — that scattering is the diagnostic signature. Lights, locks and wipers do not share a fuse or a mechanism, so when all three misbehave simultaneously the common factor is the module that controls them, not three coincidental failures.
The letter — C through F in this family, with the earlier letters covered by their own codes — is the manufacturer's index for which body control module on vehicles that use more than one. Larger vehicles sometimes split body functions across front and rear modules, or between a main module and a junction unit. There is no generic mapping from letter to physical unit; the wiring diagram for your vehicle is the only authority.
Start with power and ground before the network. A body control module that has lost a supply behaves exactly like one that has failed, and a corroded ground is both far more common and far cheaper than a module. Check system voltage too: weak batteries and failing alternators generate more communication codes than genuine module failures, and clearing a fistful of network codes after a battery replacement is a routine outcome. Body control modules almost always require programming and immobiliser-linked setup when replaced, so confirm the diagnosis properly before ordering one.
Which body control module is mine?
There is no generic answer, and any source that gives you one is guessing. The letter is assigned by the vehicle manufacturer, and the same letter refers to different physical components on different makes — sometimes on different model years of the same vehicle. The only authoritative source is the wiring diagram or service information for your exact year, make, model and body style.
A manufacturer-specific definition always outranks the generic one. If your make publishes its own meaning for this code, use that and ignore the generic description.