What you need the scanner for is to look at operationg parameters. If you don't know what you are looking at, you need to educate yourself or find someone that is proficient in doing so. Looking for codes does not always tell the story. Your symptoms are getting to where they are hard to follow and don't seem to subscribe to common issues.

Injuneer has a good guide on what parameters mean:
http://www.injuneer.com/ScanMast.html

ATC? Do you mean IAT? Sensor is spelled with an "S". Don't replace stuff without having good diagnostic reason.

 

Yeah when u find out what's going on with your car let me know, because I read your post on halloween, took my son to trick or treat and wouldn't u know it, my ac goes out and my fans won't kick, then just to better your story my car started leaking antifreeze from one of the bleeder screws, I touched the screw literally with a finger and the screw head fell off and antifreeze started gushing, I took off my shirt and put it over the gusher to protect my opti. Called chevy down here to price out a new line, 268$!!! I almost had a heart attack, I'm glad I don't have a cholesterol problem or my wife would've got a nice insurance check lol. And my ac was just worked on in june, new compressor, new lines, new condenser, new drier, then it was vacuumed to get any moisture out and new synthetic oil was added to the compressor and new r 134a was added, I was told they added what the sticker on the core support said to add. The ac has worked pretty well, then all of a sudden poof.

 

I just had the same problem with my 95 and it was the switch inside my steering column. I believe it was the ignition control switch module.

 

Control switch module??? Really? Now I know there are some differences in 94's and 95's, but is that a shared part? And is there a way to check it? Or just replace it and try your luck? Where is it in the steering column? While I'm in there I should just bypass my vats system. How much was the part and how was it that you came to that diagnosis? Were the symptoms of that being bad any different? Sorry not tryn to take over the thread but my interest is getting the better of me. I apologize, but now I've gotta find out cause now I'm having the same problem.

 

Took it to the shop, and was told that it was not sending out the signals to everything. My fans would not come on nor the ac. My turn signals and reverse lights had also stopped working at the same time. He changed out the switch and everything started working.

I may not be calling it by the right name but its the switch with a lot of wires coming from it, with a long flat plug. I think shobx has a pix of it on his web sight.

 

Sounds like the ignition switch. Shoebox's link:

http://shbox.com/ignsw/ign_switch_repl.html

 

I really hope its not my ignition switch. That looks like a pain in the rear to change. I refuse to take to a shop and pay some knuckle head 100 dollars an hour. Sorry if there are any mechanics here but I can't stand taking car to shop I never know if there telling me the truth or not. What puzzles me the most is everything works when I remove the Air Intake Tube

 

Hey I feel your pain, and my laptop won't work with any cables I can find, to plug into my car I mean, I need to do something, need a scanner or a cable to plug into a usb port and into my car, so I can get some idea what's going on with my car, the so called mechanics down here are a joke, if there's a good mechanic down here in south east texas, some body let me know. And the local checy was. Destroyed by a fire, and they rebuilt without the service manuals or a tech 1 to go with my car, so that's out.