Antilag (or other feature) activation switch wiring setup??

[BeallJK]

I first and foremost apologize for the newb question ... consider it a little bit of a learning-moment and a sanity check to ensure I am wiring correctly.

I'm looking to wire-in an anti-lag activation switch (or another feature in a similar manner).  I anticipate using a digital input circuit (for instance DI7 - Power Steering Pressure Sensor).  Im looking to install a simple single pole switch.  

My sanity check:

I'm assuming I need a pull-up resistor? 

if I set my 'On Level' to High, I will connect one leg of the switch to the ECU's 12volt power supply and the other leg of the switch to Digital Input 7 (DI7).  

When the circuit is open (no antilag desired) the 12volts does not reach the DI7 pin as the switch is in 'off' position.  Vice-versa, when the circuit is closed (antilag activated) 12volts is going through the switch (which is in the 'on' position) and reaching DI7?  

Is this the best way to do it?  Any better way?  Am I missing anything?  

Thanks in advance -  

[Adamw]

You can do either.  If your switch connects 12V to the DI, then set pull-up off, on level high.  If your switch connects to ground, then set pull-up on, on level low.  

Often a ground switch is easiest because you can find a ground almost anywhere in the car (chassis ground is fine).

[BeallJK]

Thank you Adam - I appreciate the clarification.  If I have further questions I'll check-back into this thread.  

I've always been a little foggy on when to use a pull-up resistor and your explanation helps.