U0140 U0xxx · Network (U) Medium severity
Lost Communication with Body Control Module
The body module has dropped off the bus, taking lighting, locking, windows and wipers with it in one go.
Severity guidance: Medium — drivability or emissions affected, book it in this week
Symptoms you will notice
- Lights, locks and windows all faulty
- Wipers not working
- Multiple body codes
Common causes
Ordered from most to least likely — start at the top.
- 1 BCM power or earth fault
- 2 Water ingress (very common)
- 3 CAN fault
- 4 Failed BCM
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Check the BCM fuses and earths.
- ✓ Inspect for water ingress — under-dash and footwell modules flood.
- ✓ Measure CAN at the BCM connector.
- ✓ Isolate the BCM to check whether it is dragging the bus.
Repair options
- Repair supply or earth
- Dry and seal the water ingress
- Replace and code the BCM
U0140 — frequently asked questions
Why did everything electrical fail at once? +
They share one module. That clustering is the diagnostic clue — it is a BCM or bus problem, not five separate faults.
Where does the water come from? +
Blocked scuttle drains, a leaking heater matrix or a bad screen seal. Fix the leak or the new module fails too.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.