Try unplugging all the coils individually and then plug the main coil harness in and see if it changes. Then plug 1 coil back in at a time to see if one is shorted.
CK5
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'86 Jimmy 4in Lift, 40’s, tons, 8.1 Swap- 700r4 said PNNNNN
- Thread starter GWeakland620
- Start date
This is not a dedicated trail rig, but does trailer to the destination usually. I am currently in the planning phase of doing a 52/56" spring swap, and getting back to being more road worthy.
Yeah that idea just popped into my head too!
Also where are the grounds on your harness? I know LS has 2 one lower driverside of the block and 1 at the back passenger head. Are the 8.1s the same? Make sure they are looked up.
Ok so here’s a weird one from yesterday. While working on the 8.1 swap, I grounded myself while messing with the plug wires and my hand got spicy from an electrical current. It caught me off guard, but I was able to replicate it by just touching the spark plug and having my hand on the fender. That means these coils are getting power at all times right? With a spark tester in line it’s not illuminating the light, but I definitely got bit a couple times yesterday while the key is on, but no cranking.
This is quite strange. There shouldn't be high voltage present without the ECU triggering the line high and low. Could it be triggering on noise? I can't think of what would cause that. Are you scanning the PCM to know if there is a phantom tach signal? It shouldn't happen unless the crank sensor is transitioning. Where did the coils, harness and PCM come from? Maybe there's a mismatch.
These are the connecting points of the engine harness, and the coil harness. The only wire that has power during key on is is the pink/black on the left, and the yellow on the right. The yellow then correlates to pin “D” on the coil pack. Seems everything is correct there.
It sounds to me like you are missing a ground and you became the ground…we’re you touching the coil? Or plug wire? Or plug itself?
Howell used GM schematics down to the wire colors. I don’t have the access to the gm schematics anymore but I should be able to pull something from ProDemand.
I’ve got dinner plans after work but I’ll see what I can pull so you have something to go on for a schematic.
The fact that it seems like you isolated it to one side is promising.
I’ve got dinner plans after work but I’ll see what I can pull so you have something to go on for a schematic.
The fact that it seems like you isolated it to one side is promising.
Welp, i just figured it out. Apparently some of these engines came with LS1 style coils, and that’s what my engine had on the valve covers. @Blue85 had me thinking about the pin layout, and the LS1 and literally any other LS coil are backwards from each other. I found this diagram on the same website.
So long story short, all my wiring is correct, for the wrong coils. I’ll swap the pins tomorrow and I bet I’m in good shape.
The VIN for this confirms this was all pulled from an ‘06 Yukon XL with a 4L80, but at some point the coils were swapped out for different ones.
Also explains why you got a zap, your ground was your power and your power was your ground
Yep exactly
Glad you found it. Here's the coil schematics just in case: Notice each side is fused separately. Didn't remember that so it's always good to have a schematic handy.
Swapped the pins around last night. No more issues with the coils blowing the fuse. Now I’m fighting an issue getting signal to the coils for spark. Most likely it’s a failed sensor, but without a scanner I’m shooting into the dark.
View attachment IMG_4285.mov
I have a buddy with a high dollar snap-on scanner that is going to come over Friday so we can take a look. I have an extra crank sensor on hand just in case lol.
View attachment IMG_4285.mov
I have a buddy with a high dollar snap-on scanner that is going to come over Friday so we can take a look. I have an extra crank sensor on hand just in case lol.
I was wondering if you had an tach signal or not.
What provides the tach signal?
The crank sensor. If that's missing nothing is going to work. No coil or injectors firing.
I suppose I could always check injector pulse tomorrow.
