What U0140 means
The car's other computers have stopped hearing from the body control module, which runs things like lights, wipers, door locks and often the anti-theft system. Depending on the car, some features stop working, and on some cars the engine won't start. Lost power at the module or water getting into it is the usual cause.
How the engine computer detects it
CAN messages from the body control module (BCM) are missing. Effects depend on what the BCM controls — typically interior lights, wipers, central locking, immobiliser handshake. On some cars the engine refuses to start because the immobiliser handshake fails.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- BCM unpowered Most likely
- Water ingress into BCM (often footwell-mounted) Possible
- Gateway module routing CAN messages incorrectly Less likely
How to diagnose U0140
- Check battery voltage and the battery terminals. A weak battery is a common cause of body module and network codes.
- Find the body control module (often behind the dashboard or near a footwell) and check its fuses in the fuse box.
- Look for water in the footwells and around the module, for example from a blocked A/C drain or a leaking windshield seal. Water is a common reason these modules fail.
- With the ignition off, inspect the module connectors and nearby ground points for corrosion or loose pins.
- Use a scanner that reads all modules to see whether the body module answers at all. If it doesn't, a shop checks power, ground and network wiring at the module.
- A replacement module must be programmed to the car, and on many cars the keys and anti-theft system need relearning. That usually takes a dealer or a shop with programming tools.
Vehicles that report U0140 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Mazda Mazda3 | 2010–2012 | 3 | — | |
| Jeep Cherokee | 2014–2019 | 3 | 18k |
Counts of owner complaints to the NHTSA that mention U0140 (37 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- U
- Network
- 0
- Generic (SAE) code
- 140
- Specific fault
Questions drivers ask
Can I drive with code U0140?
If the car starts and the headlights, turn signals and wipers work, you can drive carefully to a shop. If lights or wipers don't work, don't drive in the dark or in rain. If many warning lights come on or the engine or transmission acts up, stop and have it towed.
Often reported together
Codes that owners mention in the same NHTSA complaints as U0140. They can point to a shared cause, so it's worth checking them together.
- U0100Lost Communication with ECM/PCM "A"9 complaints
- U0101Lost Communication with TCM7 complaints
- U0121Lost Communication with ABS Control Module4 complaints
- U0131Lost Communication with Power Steering Control Module4 complaints
- U0146Lost Communication with Gateway "A"4 complaints
- U0155Lost Communication with Instrument Panel Cluster4 complaints
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.