2010 Tahoe loses all electrical power momentarily

Here is something I have never experienced before, and I'm hoping someone here has, or has some recommendations:

I have a 2010 Tahoe with about 260,000 miles on it. I put in a new engine and had the transmission rebuilt about 40,000 miles ago. At that time I also removed and re-loomed the factory engine harness. The car is still running the factory alternator, and the battery is less that 6 months old.

For the past few months I have had an intermittent issue where the entire vehicle seems to lose electrical power momentarily. It happens so fast that I can't be certain that EVERYTHING lose power, but it sure seems that way. The door locks cycle, the head unit reboots, the dash goes dark, and, it certainly seems that even the coils lose power and the engine stops making power. It never lasts for more than a second or so, and maybe another second for the stuff to start coming back online. It'll go days without doing this, then do it twice in one thirty minute drive. It doesn't "seem" to be related to weather or temperature. It happens more frequently under hard acceleration, but it has also happened once during braking and once at idle.

What components on these cars would effect the ENTIRE electrical system? I'm thinking battery cables? Are there any relays that could cause something like this if they start going bad? Any other ideas?

Joe

So the door locks must have power when this happens? Maybe the BCM has reserve power to unlock the doors in case of emergency...

If it seems like everything loses power, I'd start with the battery cables and main fuse first..
Bad ignition switch maybe?

mikez71 said:

So the door locks must have power when this happens? Maybe the BCM has reserve power to unlock the doors in case of emergency...

If it seems like everything loses power, I'd start with the battery cables and main fuse first..
Bad ignition switch maybe?

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I think what he's saying is that there is a glitch in the electrical, and when it initially reconnects, the door locks cycle, etc.

Like you, I'd suspect a defective battery (no matter how old it is) and/or bad battery cables and connections. Perhaps a loose ground from the transmission replacement - carefully inspect the grounds at the bell housing connection to the engine.

Have the battery properly load tested by a competent mechanic or auto parts store. Then remove the main battery cables, clean the terminals, and inspect the cables for internal rot. A voltage drop test might be of value, testing both the positive and negative connections from the battery.

Primary suspects
Battery/power ground cables
Ignition switch
Fuse box
Chaffed or broken wiring causing severe short

Yes, like Fless said, I think the door locks cycle when the power is restored. It happens so fast that its difficult to say what is happening. To Mikes point about the ignition switch, I had thought of that, so with the car running I wiggled the key around for a while thinking maybe something was loose in the switch, but that did not cause the issue to occur. I should have said that in the original post.

What / where is this main fuse?

I'm not very smart about electrical to be honest, but I'm thinking that if the problem were the battery, why would this happen? Wouldn't the alternator be supplying continuous power? I'm sure its more complicated than that, but that's how my smooth-brain imagines it.

When this happened to me, the positive cable was loose on the battery terminal. So if yours were mine, I'd check that and the cable for corrosion first. Then fire up the scan tool and check the battery's state of charge.

Chooko said:

What / where is this main fuse?

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Should be a big fuse on firewall, or right on the battery itself. Just follow the positive battery cable.
Unbolt the terminals and check for corrosion/tightness..