It's funny you bring that up about the alternator because I have to switch the battery out after every time I attempt to start it I can only turn it over three times maybe and then the battery is dead I was wondering about the alternator myself or a ground somewhere
Well that wouldve been a symptom that should have been told from the beginning. You need to understand there is a difference between a scanner(code reader) and a Bi directional scanner which is what the tech 2 is. A code reader is NOT a bi directional scanner and can NOT be used to even remotely to the level of a Tech 2. A tech 2 can be used to troubleshoot so many systems and even subsystems down to the sensor level on a vehicle. You can actually turn one injector on/off with a tech 2 for troubleshooting or even reset the security code on your radio, run your shift motor on your Tcase through all its positions and check for positive feedback of position, bleed your brake system using the ABS pump and many many other things.
A voltmeter is built into a multimeter/digital voltmeter. It is a useless tool to someone that does NOT know how to use it or interpret what information it is telling you. Sure anyone can be taught how to properly use it. Without basic DC theory knowledge it makes it harder.
Coming here bashing GM is NOT going to make people want to eagerly help you considering this is an all GM forum. Guess what...everybody here owns GM. And I hate to be the bearer of bad news...All vehicle manufacturers have their flaws, down to specific models and even engines or transmissions. A USED vehicle was sold off as used for a reason...it aint new anymore, isnt under warrant anymore and likely has some problems.
There is nothing that cant be fixed. Its just a matter is it economical to fix or not.
Now back to the beginning step on your problems which seem to be electrical related. ALWAYS check the power supply first which is your battery and alternator. Check battery voltage with a Voltmeter, not the dash gauge. It should be atleast 12.4-12.5 if not well over 13v if fully charged. There is a known problem with our chassis that causes a sitting vehicle to drain the batter down and after time will ruin the battery. A lead acid battery is NOT designed to be ran down and recharged often. If that happens then it will kill cells in the battery which prevents the battery from outputting the needed 12v+ which makes it useless. Clean your battery connections, check your alternator battery charge wire for corrosion, defects, loose connections.
Charge the battery fully to around 12.8-13.6v. Have hood release popped so you wont have to open a door (there is a reason for this) and check the next day what the battery voltage is AFTER you charged the battery fully the previous day. The voltage should be around 12.6v or higher. If it isnt then let us know. You likely have a BCM not going to sleep and running the battery down overnight. Check the ground behind the rear of the engine all the way up to the firewall for corrosion, loose connection or broken ground wire. Also check the same for the ground wire at the chassis just below drivers door right near the transition to the firewall.
Since the engine wont even start then the alternator is NOT charging your battery but it could have a bad diode inside that is shorted to ground and drawing your battery down. There are easy ways to troubleshoot that too. We will get there when you get back to the basics and let us know whats going on with that battery.
