I replace my TPS today, but I need to test it to make sure it's in range. Can I test with ignition on and hooked up at the harness and nothing else so I can access the sensor, or do all the coolant/vacuum lines have to be hooked up? Also, can I back probe the harness with a safety pin? Thanks!

 

Yeah you can test it with the throttle body still off. If it's plugged in and the key is on it will produce resistance exactly the same as it would when everything is hooked up and running.
It works basically kind of like the dimmer switch for your dash lights.
You should only have to test the voltage at the signal wire (unless there's a problem with the signal).
Personally, I just poke my lead through the insulation. You can put a dab of silicone sealer on the hole after if you're concerned about it.
Some purists would disagree with that method, but I've never had any problems.

 

Chris, thanks for answering my question, knowing this will make it much easier.