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.

Real-world scan data

Seen in

3,500

scans in the past year

Found in

0.6%

of scans

1.0%

of scans that found faults

Appears alongside · share of U0140 scans

U0100in 62.7% of scans

U0121in 47.7% of scans

U0155in 32.3% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear U0140 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX