Left Front Door Ajar Switch Circuit

The computer thinks the left front door is open, but it’s really closed. It measures switch signals from the door when it should be seeing a closed signal, around 0 volts, and it’s getting a voltage higher than that when closed.

The vehicle's computer looks for a signal around 0 volts (door closed) from the door ajar switch. If it sees +12 volts instead, it believes the door is open.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check the door ajar switch in the left front door. Disconnect it and test it with a multimeter.
2. 22. With the switch disconnected, check for continuity; it should show open circuit when the door is closed and closed circuit when it is open.
3. 33. Inspect the wiring harness between the door and body for any signs of damage, shorts, or corrosion.
4. 44. Reconnect the switch and check the voltage at the connector with the door closed, expecting around 0 volts.
5. 55. If you read +12 volts, replace the door ajar switch; if you read proper voltage, check the Body Control Module. If conditions are still normal, investigate BCM failure.

• Faulty door ajar switch
• Wiring issues in the door harness
• Corroded connectors
• Faulty Body Control Module (BCM)

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