I have a 1999 exp 4L sohc that was having the infamous failed IAC valve. I had to keep my foot on the gas to start it and keep it running. When I take it to the shop to have it checked out the tech start checking voltages and when I attempt to start it for him it will fails to start, cranks but no start. That was the first time that it had ever failed to start at all. We push it in the shop and the tech further investigates to find out that the fuel pump is not operating as well as the scan tool is unable to communicate with the computer. He says it seems as is the computer has locked out the scan tool as it does work on other similiar vehicles. The shop tells me to go to the dealer and kicks my exp to the curb. So, I tow my baby home and I figure I will do a few tests myself to see if I can find anything they missed. I test the voltage to the fuel pump at its connector to be about half of the battery voltage or about 5-6V. The relay puts out about 10-11V to the fuel pump circuit when the relay is closed. I have checked the inertia switch and it is fine and I cleaned the IAC valve as well. The battery has been checked out and is fine and I keep it fully charged. I just changed the spark plugs, fuel filter and air filter about 4k ago. The check engine light has never lit before and I never noticed the status of the "theft" light before, it would just flash and seemed normal. I have read the PATS II on this model will cause a no start condition, but would like to eliminate all possibilities before having the dealer stick it to me. The "theft" light blinks rapidly when the ignition is in the run/on? position (the position where all the dash lights come on, before cranking). I have read that this is a sign the PATS system had a trouble code. I have used the correct key with the chip in it the start the vehicle consistently. So, all you techs out there what do ya think? Start scratching your head and please help me out here. Can I clear the PATS system and retreive the code myself if neccesary? What can I do to eliminate all other possibilities? Can I apply voltage to the fuel pump to check if it operates with a higher voltage applied and how? PLEASE HELP, FORCED TO DRIVE A CHEVY, OH THE PAIN!!! E-mail me directly.