B0540Driver Door Ajar Switch Circuit
- Generic OBD-II code · Body
- How the car detects it
- Neither the public J2012 lists nor any accessible maker document define B0540, so the code is unverified. The title concerns the circuit of the switch that signals the driver door is not fully shut. The GM-era Saab 9-3 tracks this input in the body control module as B2976: subtype 02 when the line sits below 2.9 V (short to ground), 05 above 10.2 V (open or short to battery), checked with ignition on or while the alarm is armed, and the driver gets a display message. In Ford's US6133827A each ajar switch is open with the door closed and grounds the input when it opens; a failed switch can keep the courtesy lamp burning. The door-open switch itself is B0510.
- What you may notice
- Door-open warning shown although the driver door is shut
- Interior light stays on and may drain the battery
- Alarm or auto-lock behaves erratically
- Likely causes
- LikelyAjar switch in the latch or door frame stuck or corroded
- PossibleSwitch wire chafed to ground in the door hinge passage
- PossibleOpen wire or loose pin at the latch connector
- RareBody control module input faulty
- Repair
- Easy · Often possible to do yourself.Typical cost: €40 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.