HELP! Electrical Issues

[Gusco21]

Hi, everyone! New to the forum and looking to get some direction as I am relatively new to GM (previously owned Toyota Tundras/Tacomas)
I purchased a used '14 Silverado DC z71 4x4. I am having the following issues (I will try to be thorough as I do not know much about electrical):

The truck has a mount for a gooseneck. It seems in installing it the previous owner spliced the tail light wires at the very rear of the vehicle for some reason. Back under the bumper, right before some sort of module that I'm thinking relays the signal over to each light individually. The spliced wire(s) are a soft green color. 
About a month out from purchase the truck saw some rain overnight (July). The next morning it did a crank/no start. I let is sit for an hour or so and went back to it. I cycled the key a few times to see if I could hear the fuel pump and then decided to crank it and it started fine but the CEL came on. I drove it for a few miles and it eventually just went off.

Fast foward to two nights ago. It rained again and my neighbor came over at 6am to let me know my tail lights were on. I decided to crank the truck over to see if it had enough charge to crank in order to make arrangements for the morning. It did a crank/no start again. I disconnected the battery to get the lights off and about 30 minutes later reconnected it to see what it would do. The truck started up fine. BUT when I turned it off, the engine kept running. Key in off position, out of the cylinder. I pulled the fuel pump relay and it kept running, pulled the fuel pump fuse and it kept running. It didn't shut off until I found the ECM relay and pulled that. Plugged it back in, truck turned on, but would not shut off again unless I pulled the ECM relay. 

I messed with it all morning and spent hours googling the symptoms. On two occasions the truck would turn on in "reduce engine power" mode. I also noticed that even with the key in the off position, the ECM relay would click as soon as I reconnected it (power was going through to the ECM). I began killing it pulling the ECM fuse when necessary. It did throw out a P1682 a few times. I reset it a few times and a few times it would just go away on its own. One guy on a forum reported similar problems and fixed it by replacing the ignition switch. Following his logic that it's just a $30 part, I replaced it as well. I drove about 10mi roundtrip to pick up the part and upon returning home I keyed the truck off and it stayed on for about a minute but then shut off. Since I had the part and the P1682 code I decided to install the switch. Once installed, the truck started and turned off fine when I tested it (before reassembling dash/column), but then once it was fully reassembled I got a crank/no start again. Let it sit for a few minutes, tried again and it started and turned off fine. I took it for a longer drive (35 mi or so) and when I returned home it keyed on and off just fine.

I hooked up the battery to my tender that evening and left it on. That night, my wife came home from printing some pictures for a project and told me my tail lights were on again. I disconnected the battery. This morning, I reconnected it and got a crank/no start again. Pulled the ECM fuse, waited a few min, reconnected, and it fired up fine but the display said something like "turn on vehicle. Battery voltage low." I drove it like that to work and when I got here had it not shut off again. So, I pulled the ECM fuse. Ran an errand, left the truck on in the parking lot and it was still on when I got back (approx. 10 min). Got back to work and had to pull the ECM fuse to kill it and decided to disconnect battery as well because it seems several things are staying on despite the key being off.

I'd appreciate any help as I am very inexperienced in electrical work but I am mechanically inclined enough to swap parts. 

[Gusco21]

Update: I'm now getting the P1682 and a P129D fault code. Just reset them and we have rain expected tonight. So let's see how it does in the morning.

[Sierra Dan]

Gusco,

Welcome to the site.

Sorry to hear about your electricsl misfortune.

A member here named Phil (aka pgamboa)

Is our K2 generation electrical guru.

I am sure he will steer you in the right direction when he has time. 

[tbarn]

Look carefully at your underhood fuse box. have seen a few with water damage. White and green corrosion.

[Gusco21]

Thanks for the input, fellas!

I'll prod around the fuse box as soon as I get a chance and the rain lets up. I also came across a similar issue that seems easy enough to check:

 

[Gusco21]

Update: I parked the truck in reverse last night on my driveway (slight grade). So, instead of facing slightly uphill, it was slightly downhill. The P129D and P1682 codes were back in the am, but the truck started up fine and shut off fine. Drove it to drop off the kids, pulled back home, cleared the codes, and drove to work. They did not come back during that drive.

[Gusco21]

If we catch a brake from the rain this weekend I should have time to pull the fuse box and check it's condition. What is the proper procedure to do that: Disconnect battery, pull every fuse/relay and lift it up?

[Gusco21]

Anyone??

[Gusco21]

Now I'm getting an intermittent "Service Trailer Brake System"...

Still hoping for some help.

[Gusco21]

Bump

[Black02Silverado]

I wonder if you got a flooded vehicle.  With that man electrical issues that is what it sounds like. 

 

Sorry I can't help any further.

Edited September 27, 2018 by Black02Silverado

[Gusco21]

It's new to me, so it's possible. However, the issues only coming up when it rains makes me believe moisture is entering the wiring and causing the problems. I just don't have the know-how to properly test nor the money to hope an automotive electrician finds the real issue (especially since it's an intermittent issue).

BTW- got a new code today p050d (after it rained this afternoon)

[silveradosid]

p050d is an injector code if your scanner can check for miss fire counts on each cylinder

[Gusco21]

I don't think my app (using blue tooth scanner + free app) picks up misfire counts. Interesting thing is that it was running fine. Also, this am I remote started it successfully but it shut off after a minute. When I restarted it with the key, it did not have a CEL on.

I'm going to try to check the fuse panels as soon as I can (nearly took my hand off last Sunday with an angle grinder) and the ecm and BCM connections.

[Gusco21]

Downloaded another app and it read a few additional codes. I had a rough idle this am, a traction light (not the tire with TC on it, the one with the wavy lines from behind the vehicle), and had rough downshifts on my way to Dr appointment. Was fine when re-started to drive back home. I'm going to be 3+ months before I have use of my left hand so I'm stuck not being to do much :'(