ok first things first. crankc and no start condition:
Check fuel, you seem to have done that
Check spark....ONLY fo this when you get a no start condition,
IF you do not get spark, go staright the the ICM box. GM uses the purple/white wire as a RPM signal to the ECU. IIRC its a white wire that goes to the tach. (IF there is more than one purple white wire ill get a diagram to get the pin the rpm signal is) but you need to see a square wave form. if you do not have a square wave form you are losing the signal either in the ICM box or from the crank. to check that just tap straight into the crank sensor. that will give you a square wave form as well. you cannot use a volt meter. it wont work.you need a lab scope. engine codes point you in the direction of the problem. they dont tell you whats wrong. if you get a crank code, it means its lost a crank signal. but not where it has been lost.
if you have a signal coming out of the ICM box make sure its going into the ECU. this will tell you if your wire is bad in between the ICM and ECU.(common problem is the ICM conector/pigtail goes bad. wiggle this around when car is running or off to see if it starts or dies.) if your signal reaches the ECU check injector signal. IF your rpm/crank signal reached the ECU it will tell the injectors to fire. if you have dead injector signal your ecu is bad. remember to check right at the ECU. if you have injector signal....hmmmm LOL get back to me ill continue. if you dont have the equipment dont bother with this. im a firm believer in not guessing cause it costs too much money in the long run. get it fixed properly take it to a well know shop.