2019 Laramie Won't start - electrical

[Hpressman]

OK, figured I'd post this here. I was looking to install some new LED lights, got my fuse tap all ready. Was checking the fuses in the engine compartment, and took a voltmeter. Grounded the black lead of the meter to the negative terminal, and then touched the top of the fuses to see which were powered with the truck running. (I used to design electronics like a hundred years ago, so I know enough to use one of these so I thought) When I touched the top of F35, I got 14.4 volts measured and the engine shut off. Internal power systems stayed on, all the accessories. Tried restarting the truck and it wouldn't. ACC turn on and off. Lots of warnings come up now on the dash when trying to start. (video attached). I disconnected the negative terminal of the battery overnight, but today same thing. Truck won't start. Any ideas? The fuse is Electronic Control Module (ECM) / Powertrain Control Module (PCM) / eTorque Power Pack Unit (PPU) Motor Generator Unit (MGU) / Wake Up / Electric Power Steering / Active Tuned Mass Module (ATMM) / ESP


Link to video of all the messages on the screen at "startup"

 

[kapinallinen2]

Touching it with a DMM should not have caused anything that you are experiencing.
I have measured the voltages on all the fuses in the external PDP with my Fluke 87 with no ill effects.
Did the fuse blow by any chance?
Can you check for any possible codes with an OBD reader?

 

[Hpressman]

thanks for trying to help! I picked up a code scanner and it won't even connect electronically. the OBD port powers it but it won't read anything. It works on my wife's car so that's odd. The truck is "on" as it is supposed to be. I swear I didn't bang or knock anything else. I've looked at all the fuses and they all seem good. At a loss. I guess I ened to get it towed to the dealership. Of course, no warranty.

 

[ramcharger1967]

thanks for trying to help! I picked up a code scanner and it won't even connect electronically. the OBD port powers it but it won't read anything. It works on my wife's car so that's odd. The truck is "on" as it is supposed to be. I swear I didn't bang or knock anything else. I've looked at all the fuses and they all seem good. At a loss. I guess I ened to get it towed to the dealership. Of course, no warranty.

Probably coincidence. The reason your code scanner won't read is the CAN C bus is down.
First thing I would check is the radio frequency hub located behind the rear seat. Disconnect it and see if you get communication.
Probing the fuse won't hurt.

 

[kapinallinen2]

Yes, sounds like the bus is down.
Dealer service or hook up an o`scope to CAN C+ and CAN C- lines to see if they have any activity on them.
Also, might want to check F-26, security gateway fuse and F-43, data-link fuse in the Interio PDC and then start disconnecting modules.

 

[Hpressman]

Thanks everyone for the help here. After diagnosing a bit more, it appears that the PCM wake up fuse that I touched with the meter (F35) actually had a loose connection so thats why when I touched it, everything went to crap. I got a fuse tap and put it in the socket so that fits tighter (without actually using the tap part), and everything is working now. I'm sure there is a better way to make the socket for the fuse tighter, and maybe I'll look at it if this stops working. For now it is fine and I keep a little Aluminum foil in the glove box just in case I have to macguyver it at some point. This was tricky,