Truck cranks but will not start [Solved].

Correct. I ran a lead from the positive terminal of the battery to inside the cab to check grounds using a paperclip back probe. Checked the power using a multimeter, positive lead with a paperclip back probing the wires and negative lead on ground

 

You need to check the 5v reference wire to see if it is grounded out.
Unplug E4 and check pin# 23 (Blue) to see if it is grounded. Since this is normally a 5v circuit, I wouldn’t suggest using a test light (unless @Dm93 says it’s ok). I’d use ohm/continuity to ground.

Black lead to ECM bracket, red lead to pin# 23 (Blue).
See if you have continuity.

 

An ohm check would be a good test, if you find it is shorted to ground then you can use a low current test light in place and start wiggling wires and unplugging stuff while watching for it to flicker or go out.

 

2.06 0hms on the 20k setting.

I did notice wire #27 is a little exposed and has electrical tape, which is weird. Any idea what that wire goes to?

 

That's pretty low resistance, I think the next step would be to unplug connector IF1 and see if you get your 5v back at E4 Pin 23 at the PCM.

That's Pin 17 I believe, it's the shield wire for the Throttle Body Motor wires. It's normal for shield wires to look like that.

 

Do I need to remove the dash to get to IF1. The diagram attached has pretty high up

 

No the diagram is deceiving, it's actually wrapped up in the main wiring bundle below the PCM right before it goes through the firewall.

 

Sweet, I'll report back tomorrow. Have a good night guys. TY

 

If you haven’t noticed by now, DM93 is a lot better at this stuff than I am.
He does this stuff for a living. I, don’t, I don’t want to.
I don’t fix stuff until it breaks. And my motto is, “I’ll either make it better, or break it better”.

 

Don't sell yourself short you do a great job for not having a background in this stuff, you even catch stuff I miss sometimes.

 

I think both of you know your stuff. I wish I came on here a bit sooner and maybe I wouldn't have had to remove my truck bed resulting in 2 seized bolts that required me to change the heads from torx to square. Oh yeah, come to find out removing the bed doesn't expose the fuel pump at all that didn't need to get replaced in the first place!! Which leads to DM93 Slogan " Test don't guess"

 

I'm a little late to this party. As it turns out is the OP's PCM shorted or what is the final conclusion here?

 

Dm93 and Tnshooter are still helping me figure it out but it's leaning like something is shorted.

 

We haven't gotten that far yet but it looks like the 5v reeference (VC) circuit is shorted somewhere.

 

I had a bed bolt that wouldn’t move with a 4’ pipe over a 1/2 drive ratchet. I doused it with aerokroil from above, below and the middle for 6 months before it would break loose…

Sorry you’re in this situation but thanks for taking us along for the ride. Thanks too to @Dm93 & @TnShooter

 

Whenever a PCM provided 5V power is provided that is where my testing ends and I replace with a known good PCM.

The most reliable 5V signal to check for is Crank. I usually just check at the Cam sensor or even the MAF and that's usually my smoking gun for confirmation of a PCM which is DOA.

Sounds like the rat chewed up the harness and when you tried to fire it up there was a little arc arc action against the wiring or a grounded metal close by and the PCM not being fusible at its core made a little internal smoke.

Just an assumption on my end.

 

Just shorting the 5v reference circuit to ground will not kill the PCM but it will typically take it offline until the short is cleared.

 

This truck sat for a year in 2021 and I would occasionally run it but it's been my daily driver for the last 14 months. I think@dm93 said the truck will still run without the cam and OCV sensors connected. It's hard to believe a rodent chewed 4 inches of wire/conduit and made a nest in the intake manifold in 2 days vs it sitting for a year. It's very possible but I think I those wires have been like that. Who knows at this point

 

Normally, no for sure it won't kill it, but for some reason, every once in a while you do get an absolute freak accident.

I would typically check for continuity in the circuit before making the determination the PCM got fried, don't go thinking that if there is a short I would just replace it out of a huge hunch.

I'm also a HUGE proponent of the "test don't guess" method as well.

 

I've tested it on mine and it will run without one or both cam sensors but it will not run without the crank sensor.
Most vehicles will not run with a shorted 5v reference circuit although many of the newer ones have multiple 5v ref circuits and can sometimes run when one is shorted depending on what sensors it feeds.