My 2007 electrical system 'winks'
 

I have an interesting and perplexing problem. My entire electrical system 'winks', as in it totally shuts down, and immediately 'resets' itself. When I say resets, I mean that all systems come back online, but as if I was just starting the car. When it does the reset, the door locks 're-lock'. If I am driving along at night, the dashboard lights turn off, immediately followed by the headlights turning off. Then, everything returns to normal, along with the door locking again. If I manually unlock the door, it simply relocks it. If the speed control is engaged, it loses lock, AND must be restarted (set), as it loses the programmed speed. It does not 'turn off' the speed control system, but deletes the memory part of it. I have checked all the wiring under the hood, and under the car.... This has been an ongoing problem for several months now!
This past weekend, I removed the under-the-dash covers, and checked every cable, every connector, every ground point, and the various connectors on the BCM (body control module). I started this checkout by turning on the ignition, but not cranking the engine. As I stood outside the car, wondering if that was enough to allow the glitch to happen, it happened.... This was not a surprise, as the glitching has happened with me just sitting in the car, no engine running, just listening to the radio in a parking lot.
The last thing I was doing prior to this glitching starting.., was the replacement of the subframe bushings. I lowered it just enough to squeeze the bushings into place. I felt no strain on anything of the steering system, and see no wiring that could have been pulled on while I lowered the subframe. It was a couple of days later that the glitching started....., on a rainy night.
Nothing I do seems to trigger it, and there is no cyclic function to it....
Before I start adding LEDs at various points for power loss indicators, I have decided to post this...., hoping someone else has experienced this problem.....
Any ideas what I should do next?

2007 Monte Carlo LT, 350,000 miles, so far....

So it is intermittent you say and it happened after you lowered the subframe WITH the engine attached to the subframe? Sounds like there must be wires pulled.
Did you check the main connector on the firewall?

More data
 

I should have pointed out that the subframe was only 'lowered' at the rear attachments, and only by the smallest amount to allow me to replace those bushings.
Yes, I have checked all firewall connectors, and all wire bundles.
What I also did while all this was happening, was to replace the corrugated plastic bundle tubing (plastic conduit), as so much had simply disintegrated over the years.
I wiped down every wire, as there had been a lifelong oil leak from the 'front' engine oil seal. Currently, there is still an oil leak due to the oil pan gasket....
Yesterday, I was doing some more 'searching for an answer' under the hood, and tested those bundles under the engine for a 'forced' glitching.
As has been the case, it was glitching several times with no reason while I was 'probing around'...
What I did notice was that when it did its 'reset', the forced locked door was unlocked! The driver door was open, the ignition on, engine not running.
So, when the car is being driven, the doors are 'reset' to the locked position, if I have forced them to be unlocked....
And, they unlock, if the car is just sitting there, ignition on, engine not running..., if I have forced them to the locked position.
Additionally, there is a three ding, 'fast ding', upon the reset..... There are no dings when the reset occurs while driving. I do not recall ever hearing just three, fast dings.....
Dings are slower, and 'time out' to alert that the key is in, with the door open....
That's the latest noticed data....., for now....

Weekend data addition
 

I have more data on this weird problem:
The windshield wipers lose power during the glitch.
The radio lighting does not lose power during the glitch. That also is the case when I use the dimmer on the dash lights, even though it also affects the radio's lights.....!!!
Addendum to the door open, ignition on, engine off... The three fast dings, (Chimes), may be the 'brake assist system' notification....
When the 'reset' happens, the 'Tracking Control System' icon is briefly on and the notification window briefly flashes, "Service Brake Assist"...
Waiting to understand how all these indications add up to..., "Look here for the problem..."
BTW: There are no 'Chimes', icons showing, nor notification messages showing..., when the car is being driven.....
ALSO... When I remote start the car, and a glitch happens, the engine shuts off, while the interior fan stays on...
Remember, the doors must be locked, before the remote start will start the engine.
When it does start, the interior fan runs, and I think the AC compressor may even run. I base this on the fact that it's 68° right now, and the air flow got increasingly cooler.
Then, the gitch happened...., and the fan NEVER turned off, only the engine!
It just keeps getting stranger, and stranger....

Friday's data additions
 

Friday's discovery is that the door does not have to be open or closed to get the 'Traction Control System' icon and "Service Brake Assist" panel readout on the first 'wink' reset.... AND..., if you just wait for several subsequent winks, the TCS icon and the "Service Traction Control" panel readout appear, and keep appearing with each additional reset.... (Reminder: the ignition is on, and the engine is not running....)
I decided to remove the Body Control Module and test some components... Seven connectors, lots of wires on each connector.... And they are in a tight space with chassis Ty-Raps
It is an impressive board, being 20 years old.... .
I checked the two big capacitors, and they were within tolerances...
I did not attempt to test all the input bypass caps, as they so numerous, and very small SMDs....!
I checked for any visually seen physical damages or failures, using a microscope' camera.
Re-installed it, the glitch still lives.......Grrrr
And wow, the downloaded pics are huge.! They are from an Android cellphone
https://cimg4.ibsrv.net/gimg/monteca...7285413dbd.jpg
Side one of two sides
https://cimg5.ibsrv.net/gimg/monteca...e099f82ad6.jpg
Side two of two sides

This sounds like a loose or corroded battery or chassis ground. Check and clean all main grounds, battery terminals, and any fusible links as that often fixes these multi-system resets.

Thank you for the input. I have quite a nice GM service 'collection' on this 2006-20007 run. There are quite a few differences compared to prior years.
I shall be sharing some more 'data' on the problem, after I answer replies. I have been in Florida this past week, working on an old DC-3. Mr Douglas will be 85 years old on 10Apr26. My checks on wiring, and possible shorts has been rather extensive, and I have decided that the problem may not be a skinned wire....
But, it is great to know that there are folks seeing this, and making suggestions to cure it.....!

You may on the right track, though ALL ground connections have been checked. Getting to some of them was a real pain in ... ya know what..!! Corrosion at the battery is not the answer. However, the battery is becoming the suspect, IMHO... Time update the 'data' now.....
Thank you for showing support and suggesting cures.!

Today's data update.... While waiting for my breakfast a fast food establishment, I suddenly got a Traction Control, and an Anti-locking Brake System icon on the panel. Past instances were always the speed sensor at a wheel. However, this time was quite different! I no longer had any other panel indicators, including no tachometer, no fuel indicator, no temperature reading, no reading lights, no dome light, no fan (although the light for 'outside air' was on), no power to raise the window, a dim reading on the radio that said it was muted, no wipers, no power to my Garmin that covers my speedometer readout that is fed off the cigarette lighter circuit, no trunk opening control, no headlights, probably no brake lights, no door locking power, ect... Basically, I had a running engine....
I drove to my 'parking spot', and turned off the engine, discovering that I could not get the key out, due to no power for that solenoid that allow you to fully 'turn off' the car, and remove the key.
So after thinking a zillion thoughts, I decided to try to start the car again. It started normally, and all systems were back online again.....!
On this trip, I decided to bring my new OBD test unit. There were no DTCs, active or stored. When I looked at the system voltage it was 14.2 volts, normal charging voltage. But, as time went by, it slowly decreased to a point of 'winking', where it returned to 14.2 volts again. I got a friend to watch the OBD readout, while I put my voltmeter on the battery posts. It showed the same slowly decreasing voltage, until the 'wink', which he signaled me had happened. Several folks have suggested that the alternator was flaky. But, other data suggests that not be the case. One piece of data tends to put that idea to rest. With the car turned off, and the key removed, there is about a minute or two of 'Aux' power, allowing you to roll up windows, listen to that news story on the radio, ect. However, also during that gracious minute, it can also do the 'wink', and that kills the free minute, as if you had opened the door, (which it does normally)....
So, I am thinking that I may have a flaky battery. It was new 11Jul25.
And, the winks go on.......