Car will not crank

Please never never ever disconnect a battery cable with the engine running!

If you pull this stunt on the job, you might get one verbal warning if nothing is damaged, but if you a're caught the second time, you will be fired. I can describe the theory if you want me to, but the bottom line is you likely destroyed numerous computers. The anti-theft system may have kicked in.

AC generators, and GM's miserable design in particular, develop voltage spikes that are smoothed out by the battery. With no battery to do that, those spikes go right back into the generator's field to make a stronger electromagnet, and a higher output voltage. Eventually the voltage will destroy the generator's internal diodes and/or internal voltage regulator, and will damage some of the computers. The voltage regulator does its job with the battery as two parts of a team.

1987 and newer GM generators develop unusually high voltage spikes. Repeat generator failures are very common, caused by the aging of the battery. While they will still crank the engine okay, they lose their ability to dampen those voltage spikes. Any time you need to replace a defective GM generator, always replace the battery at the same time, unless it is less than about two years old.

If you get real lucky, you may have nothing more than some blown fuses, so check those first. Next, you will need a scanner to view live data and see the inputs the engine computer is seeing. Check if the transmission range sensor is indicating "park" and "neutral" at the correct times. See if the "crank" signal is showing up from the ignition switch. If all the inputs look correct, but the computer does not respond as it should, suspect the computer.

The only fuse I can find in the ignition switch and starter circuit is a 60-amp in the fuse box ahead of the right front strut tower. That is fed right from the remote battery stud. If you do not find twelve volts on either side of that fuse, the best suspect is a wire broke off the battery cable connector.

Remove the starter relay, then check for voltage on the terminals in the socket. Do this with a test light. That is more accurate than a digital voltmeter for this type of problem. Do not poke the probe into the terminals as that can stretch them and cause future intermittent connections. You should find twelve volts all the tine on one terminal and twelve volts on a second one when the ignition switch is in the "crank" position. If you are missing the second one, there is a 10-amp fuse labeled "ABS/PCM". Check that one again. It is on the left end of the dash.