Was dying, now it's dead

[Okguy]

I have a 2015 half ton WT with a 5.3. About a week ago it started cutting off while I was driving it. It was like the switch was turned off. After a second or two it would restart on it's own. I checked grounds and fuses and reseated some connectors and it got better for one trip to town, but on the next trip to town it died and I haven't been able to restart it since.

I replaced the battery about a month ago because the original battery failed. It ran fine after the battery change.

I have removed and cleaned every ground I could find, and rechecked all the fuses. All good.

When I turn the switch to run, everything comes on as it should. When I go to start everything goes totally dead. When I release the key back to run it all comes back on and the gauges all cycle just like when I first turn it on.

In the fuse box under the hood, the run/crnk relay #64 has 12v at the contact side but isn't getting a signal voltage to close the contacts. I can close the contacts manually and it powers up everything downstream - ECM relay, stater relay, and the fuses related to it. With the relay held closed I can start the truck and it will remain running until I release the relay.

I did replace the ignition switch but it didn't make any difference.

Any ideas?

[Okguy]

Crickets

[asilverblazer]

I would put a multi-meter on the battery and watch the voltage when turning the switch. 

 

For fun - take a jumper cable and go from engine to battery ground (ground the engine to the battery). I had a car do as you describe, adding an engine ground strap cured it. 

 

I've also got bad new batteries - twice in a row - that's why I'd watch voltage on it.

[Black02Silverado]

It's a long shot, but the battery cables could be corroded inside the casing not allowing current flow.  It's rare but happens.

[CrawlSlow]

You know the relay doesn't engage.  Test the relay. Maybe you got a bad relay.

[JimCost2014]

With the relay held closed I can start the truck and it will remain running until I release the relay.

 

Good call, 5 days later one of the many 1000's of members actually ready what the OP said.

I am guilty of grazing right over that comment.

[Okguy]

It is fixed. I went to check the splice under the drivers door sill and found that a piece of gravel had rubbed through a wire. It was light green with a purple tracer. I had checked that area before and vacuumed out a lot of dirt and small rocks but didn’t see anything. At the time I was just checking the condition of the splice. After double checking everything else three times I went back in and found the problem by running my fingers along the wires and felt a tiny rough spot. I had to look really close to see the problem. I could see a little bit of silver so I knew the conductor was exposed so I bent it a little bit and could see that it was rubbed through.

I’m attaching a picture. In the picture I had just peeled it back a little and twisted the ends together to test it. Afterwards I put in a proper splice and heat shrink

[CrawlSlow]

 for finding the cause. Another  for coming back to report the cause. A lot would just stay quiet and not report back. 

Edited October 29, 2021 by CrawlSlow