U0140
Lost Communication With Body Control Module
Communication / network
Generic OBD-II
High
What it means
U0140 sets when a module stops receiving expected data from the body control module (BCM) over the vehicle network. The BCM manages body electronics — lighting, locks, wipers, and often start authorization — so the fault usually points to CAN bus wiring, connectors, power/ground, or the BCM itself rather than an engine part.
High
Can I keep driving? Varies — warning lights and electrical features may act up; on vehicles where the BCM authorizes starting, a hard fault can cause a no-crank/no-start, so diagnose before relying on the car.
Common symptoms
What you'll notice
- Multiple warning lights on the dash
- Body electronics acting up (lights, wipers, locks, windows)
- Other lost-communication (U) codes stored alongside it
- On some vehicles, a no-crank/no-start if the BCM handles start authorization
Common causes
Most likely first
- Damaged CAN bus wiring or a broken splice between the BCM and the networkLikely
- Corroded or loose BCM connector, or a bad groundCommon
- Low battery voltage or a charging-system fault dropping modules off the busCommon
- Blown fuse feeding the BCMLess often
- Failed body control moduleLess often
How to diagnose & fix
Work through it in order
- Check battery voltage and the BCM power/ground and fuses first — weak power drops modules off the bus.
- Scan all modules and note any companion U-codes; the pattern points to where the bus is broken.
- Inspect the BCM connector and CAN wiring for corrosion, chafing, or breaks.
- Measure CAN bus resistance (about 60 ohms across the two lines) to find an open or short.
- If power, grounds, and wiring are good and comms don't restore, suspect the BCM itself.
FAQ
Quick answers
Is it safe to drive with U0140?+
It depends on the vehicle. Body features may misbehave and some cars won't start if the BCM authorizes the ignition. Have it diagnosed before depending on the car.
Can I just clear U0140?+
It will come back until the communication fault is fixed. If it was a one-time glitch from a low battery, address the charging system first.
Related codes
Often seen with U0140
Read & clear U0140 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX