Have a Car Question? Ask a Mechanic Online.
does the scan tool show an rpm input when you crank it?
if yes, you need to check your power and grounds into the pcm one lead on a pcm ground and the other on a pcm power input wile cranking you need to make sure you have 12 volts.
have had several ignition switch problems with a 4 volt loss from swich, normally i use a voltage drop test by putting one lead on the positve terminal of battery anr the other lead at each of the positive inputs to the ecm one at a time, this is voltage drop, which is a measurement of the amount of voltage you are loosing through the circuit this reading should not be more than .3 of a volt, any more than that and the circuit has high resistance, most commonly the ignition switch.
you need to leave the ecm plugged in and back probe each circuit the same way, voltage drop check each circuit, remember you are checking each circuit with one lead at the beginning of the circuit at the battery and the other lead at the other end at the ecm