What is the history of this vehicle? Has it ever been in high water or a front end collision?

 

A friend of mine had extremely similar issues with his 2001 Bonneville. His focus was on the BCM as well (changed many of the same parts you did) but a service shop traced the issue to a wire underneath the air cleaner box was frayed and shorting out. That wire was fixed and the car has been operating flawlessly since.

I'm not saying you have the exact same problem but sometimes electrical issues are caused by the darndest things.

 

Never had damage due to either , it was driven by my brother since new on a lease and I bought it at 66K in 2005 .

 

Anyone ?

I'm trying to find out where the G201 Ground splice pack is located . 2002 Impala base

 

I think I may have found where this issue is coming from .
Through removal of each component mounted on the dash one by one and spraying contact cleaner in plugs and applying dielectric grease , I did the bcm first , then the headlight switch , and the instrument cluster . None of those made any difference .

Then , I pulled the radio .. and THERE WAS THE GROUND I WAS LOOKING FOR behind the radio . No , I'm not 100% sure it wasn't the radio and not the ground , but cleaned and greased the radio plug and removed and cleaned the ground behind it .

Hasn't done it since , but time will tell .

 

Long shot considering this is ten years later, but if you see this, did your issue ever end up being resolved by servicing the ground location behind the radio? I’m suffering from very similar symptoms as you describe above, with the addition of the radio not functioning due to being theft locked, and my scan tools aren’t don’t pick up the bcm during any scans

 

given the o.p. only logged onto the site for about 10 days, 11 years ago, no, you aren't going to get a response from that user.

But, you would only pull the radio and check/clean that ground ONLY IF it fixed the problem for the o.p.?

 

Well no, I’ve been considering putting in an aftermarket radio, even though the stock one is fully functional, because the issue (or issues) causes the radio to go into theft lock. My thought process is that an aftermarket stereo would not be subject to the theft deterrent system of the vehicle, and since it receives power and functions otherwise normally, especially if I reset the BCM which allows it to do so for about 10 minutes before all the electrical systems in the car start going bananas on account of whatever the problem is, it would be a good opportunity to get behind the dash and take a better look around for the problems source.

It’s a frustrating thing to deal with, but I purchased the car as an a to b vehicle so I can get to work while I finish fixing my primary car, so I’m both not super inclined to try fixing all the issues and don’t really have the space to do it either, but no music to deafen the exhaust, engine knock, and poorly shifting transmission is getting a bit dull.

if you’re curious, electrical symptoms are:

Nonfunctional electric door locks

Nonfunctional rear window heating element

Nonfunctional electronic trunk release b

Nonfunctional keyfob (confirmed keyfob is not dead and is programmed to car)

Constant cycling of the following warning messages: service vehicle, battery light, security light, coolant level low, change oil, as well as the airbag light, and multiple u1000 codes involving a class II data communication failure

Overheating, especially in traffic, confirmed this is because the electric radiator fans are not turning on at either the correct speed or at all when the engine hits temperature, and this results in a teeter totter between about 200° F and 230° F (not confidence inspiring)

Engine knock is either piston slap or a chewed cam lobe/something between a lifter and a valve, can’t be rod knock because it runs fine and has been the last 300 miles despite it being plenty noisy

and finally, goofy transmission shifting issues relating to a maximum shift adapt codes. So it’s kind of a headache of a car that I’m hoping maybe I can make slightly less of a headache in the short term. Thank you for the response by the way