U0142
Lost Communication With Body Control Module "B"
- Severity
- High
- Driving
- Drivable — book it in
The control module has stopped receiving messages from body control module "B". This module sits at the centre of the vehicle's networks - a gateway passes messages between the separate buses, and a body control module runs much of the vehicle's electrical behaviour. When one of these goes quiet, everything that depended on it goes quiet too, so expect a long list of other fault codes that are consequences rather than separate problems.
Possible causes
- CommonLow battery voltage or a discharged battery, dropping modules off the bus
- CommonBlown fuse or corroded earth on the supply to body control module "B"
- CommonDamaged, chafed or corroded bus wiring
- CommonWater ingress at the module - these often sit low in the footwell or behind a wheel arch
- PossibleFailed module
- PossibleAftermarket electrical work spliced into the bus
- PossibleModule not coded or configured after a previous repair or replacement
What you might notice
- A large number of fault codes across unrelated systems
- Several warning lights on at once
- Scan tool cannot see whole groups of modules
- Central locking, lighting, wipers or windows behaving strangely
- Battery draining overnight
- Vehicle may not start
What to check, in order
- Fix this before chasing anything else. When a gateway or body control module is missing, most of the other codes stored are symptoms of this one, and diagnosing them individually wastes a great deal of time.
- Check battery voltage and state of charge before anything else. A weak or failing battery drops modules off the bus and sets lost-communication codes with no wiring fault at all - this is the single most common false lead in this whole family.
- Check whether this code is current or historic. Lost-communication codes are routinely set by a flat battery, a jump start or a battery disconnection, and a historic code straight after one of those events usually records the event rather than a fault.
- Check the fuses and earth points for body control module "B".
- Look for water. These modules are commonly mounted in footwells, under seats or behind wheel arch liners, and a blocked drain or a leaking screen seal is a frequent cause.
- Ask what was done to the car recently. Aftermarket alarms, trackers and tow bar wiring spliced into the bus are a common cause.
- Record the full code list before clearing anything. After the repair, clear them and see which ones actually come back - usually far fewer than were stored.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
U00xxU01xxU02xxU03xxU04xxU05xxU06xxU07xxU08xxU09xxU0AxxU0BxxU0CxxU0DxxU0ExxU0FxxU10xxU11xxU12xxU13xxU14xxU15xxU16xxU17xxU18xxU19xxU1AxxU1BxxU1CxxU1DxxU1ExxU1FxxU20xxU21xxU22xxU23xxU24xxU25xxU26xxU27xxU28xxU29xxU2AxxU2BxxU2CxxU2DxxU2ExxU2FxxU30xxU31xxU32xxU33xxU34xxU35xxU36xxU37xxU38xxU39xxU3AxxU3BxxU3CxxU3DxxU3ExxU3Fxx
Network communication
U0100U0101U0102U0103U0104U0105U0106U0107U0108U0109U0110U0111U0112U0113U0114U0115U0116U0117U0118U0119U0120U0121U0122U0123U0124U0125U0126U0127U0128U0129U0130U0131U0132U0133U0134U0135U0136U0137U0138U0139U0140U0141U0142U0143U0144U0145U0146U0147U0148U0149U0150U0151U0152U0153U0154U0155U0156U0157U0158U0159U0160U0161U0162U0163U0164U0165U0166U0167U0168U0169U0170U0171U0172U0173U0174U0175U0176U0177U0178U0179U0180U0181U0182U0183U0184U0185U0186U0187U0188U0189U0190U0191U0192U0193U0194U0195U0196U0197U0198U0199