U0140: OBD-II code U0140 flags loss of communication with the body control module — the network can no longer see the BCM, which manages lighting, locks, and comfort features.

Symptoms

• Check engine light is on along with various body-electrical warnings on the instrument cluster.
• Interior and exterior lights, power windows, door locks, or the immobiliser may behave erratically or fail entirely.
• Instrument cluster warning lights may flicker or stay illuminated because the cluster stops receiving BCM messages.

Common causes

• A failed BCM — the module itself has gone offline due to internal failure or water damage.
• A CAN bus fault (broken wire or short) between the BCM and the rest of the network.
• Loss of power or ground at the BCM — blown fuse or corroded connector, often after body or interior water intrusion.

What to do?

Confirm the BCM has power and ground at its connector. Check the BCM fuses. Measure CAN bus continuity to the BCM. Look for water intrusion around the module (BCMs often live under the dash or kick panel). Replace and program to the vehicle if the hardware has failed.