Ground issues? No crank, no start, no obd2, 1h later works as usual

[m1dn]

Was going to school bus stop this morning, opened car, threw in backpack for the gym, closed and tried remote start, lights blinked but no crank.
Got back from bus stop, put the key in and car won't crank nor start.

All the dash lights come on, radio works, AC works, all gauges works.
When i turn the key, the rpm gauge goes up then back down, but car won't crank and started won't click, nothing, silence.
Stick in the OBD2 scanner, there's power in OBD2 port, but it can't connect to the computer, wtf?

Grab another car, go to gym frustrated, come back maybe ~1h later, grab the keys and truck start as usual, wtf?
Few engine light codes stay pending afterwards - P069E ( fuel pump module ), P0700 ( TCM ), P2544 ( Torque smthn? ), U0073 ( Control Module comm Bus A off ).
Reset the codes and truck runs/starts as usual, no issues anymore.

Wondering if someone had anything similar happen and what it ended up being?
It started around since when i moved top Ground Cable from being connected to back of the block to middle block hole, above the exhaust manifold.
( I was installing clamp on the back to push the broken exhaust manifold bolt and forgot to put the ground back in it's spot, so i thought why not stick it into hole closer, same block, right? )
I can't imagine this being an issue, but nevertheless i'll go get new ground cable and attach to the back of the block again.

Are there any other grounds i should be checking? There's one going from battery to the front pass side of the engine, it seems fine
Should i unplug each of the modules that threw an err and add some dielectric grease?

P.S It dropped to negative celsius overnight today, if that has to do anything with it.

 

[Doubeleive]

I would do that ground cable and check your starter cables also, that's a good place to start anyway. no pun intended.

 

[m1dn]

Cleaned up ALL the grounds, didn't find anything obviously bad.
The ground on driver side is rusty in few spots and looks like it could be stripped as well, no local parts stores have it in stock, so i'll order one

Cleaned and added dielectric grease to TCM connectors.

Started it and ran for few miles, not seeing any issues, but they were never persistent either.
Guess i'll see in few days, if it continues, i'll start with replacing ground cables and then head over to the TCM if that doesn't fix it.

 

[TahoeSquirrel]

Was going to school bus stop this morning, opened car, threw in backpack for the gym, closed and tried remote start, lights blinked but no crank.
Got back from bus stop, put the key in and car won't crank nor start.

All the dash lights come on, radio works, AC works, all gauges works.
When i turn the key, the rpm gauge goes up then back down, but car won't crank and started won't click, nothing, silence.
Stick in the OBD2 scanner, there's power in OBD2 port, but it can't connect to the computer, wtf?

Grab another car, go to gym frustrated, come back maybe ~1h later, grab the keys and truck start as usual, wtf?
Few engine light codes stay pending afterwards - P069E ( fuel pump module ), P0700 ( TCM ), P2544 ( Torque smthn? ), U0073 ( Control Module comm Bus A off ).
Reset the codes and truck runs/starts as usual, no issues anymore.

Wondering if someone had anything similar happen and what it ended up being?
It started around since when i moved top Ground Cable from being connected to back of the block to middle block hole, above the exhaust manifold.
( I was installing clamp on the back to push the broken exhaust manifold bolt and forgot to put the ground back in it's spot, so i thought why not stick it into hole closer, same block, right? )
I can't imagine this being an issue, but nevertheless i'll go get new ground cable and attach to the back of the block again.

Are there any other grounds i should be checking? There's one going from battery to the front pass side of the engine, it seems fine
Should i unplug each of the modules that threw an err and add some dielectric grease?

P.S It dropped to negative celsius overnight today, if that has to do anything with it.

Bro I cleaned every dam ground on my truck and added one from the battery to the firewall , drove it , Good

 

[TahoeSquirrel]

Cleaned up ALL the grounds, didn't find anything obviously bad.
The ground on driver side is rusty in few spots and looks like it could be stripped as well, no local parts stores have it in stock, so i'll order one

Cleaned and added dielectric grease to TCM connectors.

Started it and ran for few miles, not seeing any issues, but they were never persistent either.
Guess i'll see in few days, if it continues, i'll start with replacing ground cables and then head over to the TCM if that doesn't fix it.

Same here , replaced ground and reseated all others , no electrical issues, drove it on bumpy roads