U0140 to U0150 and U0180 to U0183: body control, gateway and lighting modules

What does U0140 mean?

The body control module runs much of what is not the engine: the exterior and interior lights, the locks, the wipers, the horn and often the alarm. A gateway is the junction between the car's networks: it passes messages from one to another and to the diagnostic socket. When either goes silent, many functions can stop at once and other modules store codes about it. Lighting modules aim the headlights or switch them on automatically, so a lost one can leave the lights fixed or dark.

What causes U0140?

1. A body control module that has lost power through a blown fuse or a burnt connector
2. Water reaching a module under the dashboard or in a footwell, often through a blocked drain or a windshield leak
3. A gateway that has failed or lost its supply, which hides other modules from the scan tool
4. A failing battery making a module reset or shut down
5. A short in a lighting circuit that a module has switched off to protect itself

What to check first for U0140

• Check which functions work: headlights, brake lights, wipers, locks and horn
• Look for water in the footwells and under the carpets near the body control module
• Check the module's fuses and the main supply and ground at its connectors
• If the scan tool cannot reach several modules at once, check the gateway first

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