1 How much gas should be in the tank when the low gas light comes on.
2 Is there a way to test the pressure sensor with out pulling the tank and if it were bad wouldn't the OBDII set a code
3 And can a small vacuum leak be missed by the OBDII
4 Any one how about you Rusty Nuts

 

the pressure sensor usually sets a code if its stuck all the way on or off. but if its barely working it might not

no idea on how to test the sensor, at work we just hook the scanner up and see where its supposed to be at default. i actually have a used one i know works laying around to replace it to see if that fixes it, or you can just blow in it to see if the reading change. theres probably same way to check it using one of the wires and seeing if the voltages change when pressure or vacuum is applied just not sure of the specs

 

This may sound weird.But you would think if and when the low fuel light comes on, the tank would be less than a gallon.I had the same question when I first bought mine.Come to find out I have about 6 gallons of gas when the low fuel light comes on.I have a 17 gallon abs tank on mine.It takes 11 gallons of gas to refill my tank.Next time the low light comes on.Go ahead and fill the tank up.The amount of gallons you just put in, will determine how much gas you had in the tank when the light come son.It seems GM did this to save from burning up the fuel pump.