Network communication (U-codes) · Network · generic (SAE-defined)
U0140: Lost Communication With Body Control Module
U0140 means one or more modules are no longer receiving network messages from the body control module (BCM), which manages many interior and exterior electrical features.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How U0140 sets
The BCM shares data such as lighting, door, and security status over the controller area network (CAN). When another module stops receiving BCM messages for longer than the allowed window, it records U0140. Conditions vary by manufacturer.
Common causes of U0140
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Low battery voltage
- Blown BCM fuse
- Corroded or loose BCM connector
- Water leak reaching the BCM
- Damaged CAN wiring to the BCM
- Poor BCM ground
- Failed BCM
U0140 symptoms
- Warning lights on the dash
- Exterior or interior lights not working properly
- Power locks, windows, or wipers acting erratically
- Security light on or no-start
- Battery draining overnight
How U0140 is diagnosed
- Scan all modules and see if the BCM responds directly.
- Test battery and charging voltage.
- Check BCM fuses and power feeds.
- Inspect the BCM and its connectors for water intrusion or corrosion.
- Verify BCM grounds and CAN wiring continuity.
- Check for software updates before replacing the module.
Typical fixes for U0140
- Repair battery or charging faults
- Replace fuses and correct the cause
- Repair water leaks and corroded connectors
- Repair CAN wiring or grounds
- Replace and program the BCM if confirmed faulty
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
U0140 FAQ
What does code U0140 mean?
U0140 means one or more modules are no longer receiving network messages from the body control module (BCM), which manages many interior and exterior electrical features. The standard definition is "Lost Communication With Body Control Module."
Can I drive with a U0140 code?
Often yes, but check that lights, wipers, and turn signals work before driving. Depending on the vehicle, the security system may also prevent starting, so diagnose it soon.
Can a water leak cause U0140?
Yes. The BCM is often mounted in the footwell or under the dash, where leaks from the windshield or cowl can reach it.
Will a new BCM work right away?
Many replacement BCMs need programming and security setup before they work properly, so follow factory procedures.
Keep researching
More network communication (u-codes) codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.