U0140
Lost Communication with Body Control Module
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.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
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
Ordered by how often each turns out to be the cause.
- BCM unpoweredCommon
- Water ingress into BCM (often footwell-mounted)Possible
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- Body Control Module
- CAN Bus Wiring
U0140 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.