I recently replaced the alternator in my 2001 Monte Carlo. Now it won't start, and the display flashes between the Battery warning and the Security warning. The radio also says Error. I figure I messed up the PCM or something. The battery is still good. I have read of a couple of different ways to reset the PCM, but so far none have worked. Many of the methods say that the security warning should shut off if you sit on accessory for over ten minutes. Mine doesn't stop. Instead, it beeps at me, and the display says High Beam Out, Low Fuel, and Service Car Soon. It cycles through those twice, and then starts with Battery and Security again. I have tried flashing the lights. I have tried disconnecting and reconnecting the battery. It just won't cooperate. Any suggestions?

 

I might start with disconnecting the battery overnight ( this gives it all a chance to reboot) and then reconnect it in the Morning and do the positive side first.
The battery will draw on the cars essential computer workings all the time.
So it may need a charge, sometimes when you change the alternator by the time you do the battery has been compromised. It should have a 14.2 to 14.8 charge on it anything below a 12 the battery could be bad.
You may have a bad ground or something and it now has showed up.
If the battery is 3 years old or older I would think about a replacement.
I just replaced the one I had and it was about 3.5 years old, but the case had a bulge in it, after I replaced it it seemed to run & start much better.

 

Okay. I replaced the battery. The security and error displays have turned off, but it's still no crank no start. I'm going to leave it disconnected overnight and hope for the best. I tested all of the fuses and relays, and checked the connections to the alternator and starter with a voltmeter. With the car off, everything registers as 12.5 volts. If it still doesn't work in the morning, I may try putting the old alternator back in. The new one is a refurb and looks a bit worse than the old one. That's what I get for having my husband pick replacement parts.

 

I left it disconnected overnight. It still won't start or crank and the display still endlessly flashes between Battery and Security lights.

 

Well that sucks for sure. So what I have done is Checked with my service tech. He indicated that the Ground could be not making the proper contact. Follow the Black wires they are usually the ground.
Could be battery ground or the normal ground from the alternator. It could also be the Starter went bad in that case it won't do anything either, if the starter is still good it should Click, if it is silent it could be bad. Check at the parts store on the warranty in case it is bad right out of the box. Most of this stuff comes in from China and it may not be good stuff
Also the connections (or Plugs could have corrosion on them, they should be cleaned as well) ( remove any green or Turquoise stains on them)
Get some terminal cleaner for that. Sometimes a pencil eraser will clean it off too.
He suggested taking the Alternator back and get a fresh one maybe they didn't hook something up when it was rebuilt. Even the best of the rebuilt stuff sometimes won't work.
I also checked with a google search and you can click the link then pick the one that you want to view and see if that helps.

https://www.google.com/search?q=yout...nt=firefox-b-1

 

I checked all of the grounds. They check out fine. It this point I'm fairly sure it's an issue with the PCM, possibly with it's connection to the ignition cylinder. Problem is, some yahoo welded the metal plate under the steering wheel in place so I can't access the ignition cylinder. Maybe I can disconnect it from the PCM side.

 

I probably just messed the car up even more by being an idiot. I figured my best option at this point is to cave in and take it to a shop. I tried to start the car by having my husband turn the key while I ran electricity directly from the battery to the starter, bypassing the ignition cylinder/starter connection. I am pretty sure that the PCM lock is simply refusing to send power to the starter because I triggered the security alert, so I thought simply bypassing it would work. The starter clicked, but didn't turn. Also, the power shuts off completely whenever you turn the key now, as if the battery has been disconnected. The power only comes back if you disconnect and reconnect the battery, and it shuts down again when you turn the key. I probably blew the fusable link or something. Gonna take the starter out and check it tomorrow.

 

Did it get fixed?