Toyota Repair: OBD II computer, input sensors, obd ii

Question
April 18, 2008
God bless you. Question is: when car is turned off and you disconnect a sensor connector, like the O2 sensor, will the car computer detect that the cable was disconnected while it was turned off? You are the expert, that’s why I’m asking.
Regards, Otto  

Answer
The answer to that would be no, the ECM will only detect a problem under operating conditions when it needs to see signals from various input sensors. If the connector is removed and left off and the engine is started then the check engine light will turn on but if it was disconnected and put back with the ignition off and the engine not runniong it can't turn the light on.