I know this is a common issue, but after checking just about everywhere and trying just about everything, I am still having issues.

To be kinda brief:
Car wont start, but can hear relay click from left fuse panel. Security Light Blinks.
Auto Door locks on the doors and the fob doesn't work, Dome Light does not work.
Radio displays the time for about 6 seconds and then nothing, but chimes do play.
using the DISP button on the radio does nothing no matter how long it is pressed.
Dash lights do seem to work as well as ac/fans.

What I have tried, is the relearn process, 10, 12, 15 and 30 min intervals. (all separate test 3 times each) relearn does not work and the security light never quits flashing.

I replaced the Ignition Switch, and tried relearn again. same result nada.
I then replaces the cylinder and key, did the relearn, and again after each interval the security light still flashes and car still does not start.

All Fuses have been checked, reseated, cleaned, and then replaced. Relays were juggled around from one location to another.

My next option is a New BCM, which I hope will let it relearn and let me start, all the GM dealers are gone around here so it is not easy to get to one to reprogram, I would at least try to drive it to one to program if I need to.

So any new ideas?
and thanks.

and btw this car does have weird electrical history. about 4 years ago, it would shut down while driving, all the dash lights going dead, but would restart. I replaced the ignition switch then, which fixed that problem.

 

I'm having the same problem intermittently. Replaced all the parts you did. For me it WASN'T the BCM but now I have a spare BCM floating around. If you wanna try it I can sell it to you. But I don't think that's the issue, my only way to fix it is to disconnect the battery cables and touch them togethor for a minute.

 

Check your battery connections at the battery, the starter solenoid and the ground on transaxle. Make sure they are clean and tight. Have your battery checked (could have a bad cell), your alternator (insufficient output) and your battery cables (possible excessive resistance). Charge your battery so you have a full charge on it, then do the relearn: Key ON for 11 minutes/10 seconds OFF. Repeat 3 times and it should reset the security system.

 

The battery is brand new, I replaced the old one just in case (it did check out ok). but touching the pos and neg is new idea. l tried that and doing a relearn now. See what happens. I do have a new bcm coming in tomorrow, but thanks anyway.

as to the cables they all seem tight, I did loosen again, cleaned and retighten.
The issue with relearn has been the security light never stops flashing after the 10-12 min. but I then try the 2nd and 3rd time anyway. but same results.
but I will see what happens in a few more minutes this time

 

anyone know what the chime codes are? there seems to be a pattern when they play.
and any idea why the security light does not stop flashing on a relearn
or why the auto door locks would not work?
btw the day before, there were no issues, car was parked overnight in garage when this problem started

 

Thats exactly the issue I am having. It comes and goes... Iv yet to solve it. Except my door locks have always worked. but the light just keeps on blinking. Let me know if you figure it out Cause Im still woried it wont start on me on a very important day

 

still no luck just the flashing security light. working on this since last Saturday. amazes me how many people have same issue, and it works for some and not others, or the problem keeps coming back.

 

I agree wit 03SSLE, check chassis ground connections from battery and alternator

 

the car is now running again.
Everything is back working except the radio is locked.
Final thing that fixed it was a new AC/Delco BCM I got from Amazon for $120.
Plugged it in and immediately things started working like the door locks and dome light.
I did have to go thru the 30 min relearn.
Now to figure out how to unlock the radio.

 

Dealer would need to program the BCM fully to unlock it.
You can use 5, track forward and power pressed at the same time to bypass the lock while the car is running.