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Discussion Starter #1
Looking for some information from the community...

A little bit about the Jeep = 1993 4.0L, AX-15, 231J with SYE, Ford 8.8 rear, Jeep Wagoneer Dana 44 front CAD deleted, 4.56 gears and 35" tires. This is just the basic stuff and (probably) not necessary for the question.

I am swapping in a 2003 GM 5.3L Gen III and 4L60E with the 231. I want to retain the factory gauges for now (dont have the $1300 for new gauges).

I know I have to use the existing sending units to use the oil and temp gauges, and a converter for the tach. Where I am running into issues and cant seem to find the information is in wiring the oil and temp gauges in.

Most sites say to use the existing sending units and leave the wiring plugged in as it is. I thought it would be that simple - until I traced the wires (temp only as I havent gotten to the oil yet) and found the water temp sender (tan/black wire) runs from the sender to the PCM. I believe I read it goes into pin 47. Logic says there is another wire that would send signal back to the gauge so that it can read the signal.

I am hoping to be able to just run the wire from the sender to the gauge and take the PCM out of the equation. The entire engine harness and PCM need to go away! If someone can shed light on this it would truly be appreciated. General logic tells me yes ... but this is a Jeep!

TIA!
 

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I don't know if this will work but here's a thought.
1987-1990 gauges don't run through the PCM. They might be a direct replacement for your existing temp and oil pressure gauges or might fit with just a slight modification.
You should be able to pick up 12V somewhere in your gauge cluster and connect that to the (+) side of the gauge. Then run a wire from the (-) gauge terminal to each sending unit. You might even be able to use an entire gauge cluster from a early YJ and have the luxury of a clock rather than your 4X4 light that doesn't work anyhow since you removed your CAD.
The early YJ gauge cluster will require some re-wiring. I'd do whatever was the simplest that worked and looked like factory.

Let us know what ends up working for you.

Good Luck, L.M.
 

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I would pull up some wiring diagrams to figure out what's what. I'm not sure how much of it runs through the computer that's something I would check. I'm assuming those senders may talk to that factory yj computer. Maybe you can direct wire them and just rip out that computer all together.

I chucked my computer out as I ran aftermarket gauges and sbc. Warning though if you chuck the computer the speedo wont work and you will have to bypass auto shutdown. Also I converted to mechanical speedo as it made wiring simpler.
 

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I added a second set of sending units for the water temp and oil pressure. I put in aftermarket gauges but it would still work for the factory gauges. You can put your second temp sending unit in the passenger side head. The factory sending unit is in the drivers side head on my 2005 5.3L. Use the factory S/U for the PCM. For the second oil pressure S/U I drilled and tapped the aluminum manifold for the oil filter that bolts to the block on the drivers side. Take a look at it there is an obvious place to drill the hole and tap it for the second S/U. Hope this helps.
 

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I added a second set of sending units for the water temp and oil pressure. I put in aftermarket gauges but it would still work for the factory gauges. You can put your second temp sending unit in the passenger side head. The factory sending unit is in the drivers side head on my 2005 5.3L. Use the factory S/U for the PCM. For the second oil pressure S/U I drilled and tapped the aluminum manifold for the oil filter that bolts to the block on the drivers side. Take a look at it there is an obvious place to drill the hole and tap it for the second S/U. Hope this helps.


This is the only way that I can fathom accomplishing what you want to accomplish and not that hard to do it seems.
 

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Discussion Starter #6 (Edited)
clarification (maybe)

So I know the 5.3 senders will be used for the 5.3 PCM, I am good with that part. I am going to take the stock Jeep PCM out of the equation entirely. I appreciate the information on where to put the Jeep sending units onto the 5.3! I know there will be two sets of sending units - Jeep and GM.

What I am looking for is how the stock Jeep senders will work with the stock Jeep gauges... with wires going to the PCM can I just cut and splice the wires and have the gauges functional? It used to be sending units just had one wire, the Jeep uses a 2 wire connector. The engine temperature sender has a tan with black (tn/bl) stripe and a black with light blue stripe (bl/lb). The bl/lb goes to a large splice with other same colored wires - assuming this is just a common ground since other senders/sensors trace back with the same bl/lb wire. The tn/bl wire goes to the PCM 60 pin connector. I have been through the wiring diagram, but while I can read other diagrams electrical stuff just doesnt make sense. However, I think it shows the wire going to the gauge is violet with yellow stripe (vt/yl). My thought is to splice the tn/bl to the vt/yl wire and the bl/lb wire to another common ground. This way the sender and the connector are reused and I can keep the wiring clean. Does this sound right? Logic says yes ... but its a Jeep!

I know the early YJ gauges did not send the signal through the PCM but I am hoping to not have to spend more money on gauges at all (new or old). I am also hoping to keep my time minimal on the inside of the Jeep and not having to rewire the underdash area (or make problems by disturbing the 26 year old loom).

Overall information on making the gauges work with the new engine/transmission is what I am going for. I have not seen a write up on doing this (maybe its time for me to do one with some help)...

It was all so clear in my head what I was asking but after reading the original post again ... I am surprised I got the replies I did! Thanks again to those that posted, hope this clarification makes sense!
 

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I'm not sure what you want to do is possible...
Why not just keep the jeep pcm in place to run the gauges and remove the un needed portions of the harness.

Iirc your common sensor splice isn't ground, it's 5v reference.
 

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Yes, If you have identified the correct gauge wires and have removed your Jeep PCM, all you have to do is splice those wires to your second set of senders. I don't see any reason why that wont work. Your Jeep gauges should be getting their power from under the jeep dash.

Not sure if your Jeep water temp sender is the same thread pitch as the GM but if not just find one at Summit that will fit your application.
 

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You don't need the Jeep PCM. About all it does for you would be to provide 12VDC or 5VDC to any sensors (where applicable). Without the PCM you'll need to source a new 5VDC+ or get one from the GM PCM. Then wire all the outputs back to the gauges. 92-95 gauges are worth saving.
 

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Discussion Starter #11
Thanks

Thank you for the info - I am hoping to get it all worked out in the coming days. I will work on putting a write up together in case others want to do the same and let those who posted here know if it works!
 
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