I'm doing a project on my car where I have a clutch position sensor that moves when the clutch throw-out arm moves. Due to some new improvements on the car I need to have the ability to bypass the sensor on occasion, yet simulate the operation has occurred to the transmission control unit. The sensor sweep is 4.75 volts to a little less than 1 volt. The modification will prevent the sensor from actually moving on certain occasions. I want to intercept the sweep signal using a relay, then reproduce it electrically to send back to the TCU. How can I reproduce a drop from 4.5 volts to about 1 volt electrically? I friend mentioned using a 555 timer, but I have no idea what the values would be to achieve these results.

 

What type of sensor is this? Is it a mechanical limit switch type sensor, is it a hall effect proximity sensor or is it something else? Also, you mentioned the sensor sweep was 4.5 - 1V. Does that mean that the sensor is outputing 4.5V normally and then it drops to 1V when the clutch throw-out arm moves or vice versa or what? What is the input voltage of the sensor? 12V, 4.5V or something else? During times when you want to bypass this sensor, how would that be done? Would you do it with a button or switch in the passenger compartment or by another method? You need to provide some more details about what it is exactly you're trying to do.