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LS Swap Electrical Help

Nkldrgr

Active member
Joined
Jul 25, 2020
Member Number
2362
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I needs some info, guidance, or direction. I want to put an LQ4 in my 2005 LJ.

What I need to know is how much of the factory Jeep wire harness do I need to keep or get rid of?
If I simply strip out the engine electrical components and trans components, will I trigger Jeep computer problems?
If I save wiring like A/C, gauges, starter, etc; can they simply be spliced into the LQ4 harness?
Do I need to have two OBDII ports; one or each computer?
I want all the factory gauges and controls to work, and no CEL/MILs.

I built a stand alone harness from my Willys. I'm not afraid of wiring, I just don't know what I'm doing.

Thanks in advance.
 
I needs some info, guidance, or direction. I want to put an LQ4 in my 2005 LJ.

What I need to know is how much of the factory Jeep wire harness do I need to keep or get rid of?
If I simply strip out the engine electrical components and trans components, will I trigger Jeep computer problems?
If I save wiring like A/C, gauges, starter, etc; can they simply be spliced into the LQ4 harness?
Do I need to have two OBDII ports; one or each computer?
I want all the factory gauges and controls to work, and no CEL/MILs.

I built a stand alone harness from my Willys. I'm not afraid of wiring, I just don't know what I'm doing.

Thanks in advance.

I hate to send you back over to pirate but the 5.3 in Jeep’s thread will answer all your questions. From what I’ve read some guys with tj’s are running both computers to run all the Chrysler stuff and one to run just the motor. Keeping factory gauge cluster has been the hardest part. I’m half way through reading and so far no one had done it successfully.

https://www.pirate4x4.com/threads/5-3-jeeps.735270/
 
I was afraid someone was going to say that. I went through about 25 pages of the 385...lots of trash to wade through in there. Guess I'll started reading...
 
I’m swapping an L33 into my LJ and plan on using both computers. I pulled the oil pressure and water temp sensor from the jeep motor and installed them in the LS block along with the original LS sensors. I’m hoping they will run the jeep gauges while the LS sensors will keep the LS computer happy. As far as the stock tach goes, Novak makes a doohickey that should run it. I also plan on using the jeep wiring to run the AC compressor. Theoretically, one OBD2 port for the LS should be all thats required.
Now I’m still a long way from firing mine up but I think everything should work as described above.
 
I thought someone mentioned calling Nevada Speedometer on one of the forums for the speed sensor. Off memory it sounded like they had a cable made that used a mechanical wheel that went to a VSS and that made everything happy.

I think it could be done and it would make an AWESOME writeup, it might just require you to find out exactly what wires in your dash control what gauges, and matching those to the LS PCM.
 
I guess I'll update my own questions.

My first questions was about how much wire I need to ditch from the factory Jeep harness. Well, I just looked at a running driving LS swapped Wrangler that had NOTHING cut out of the Jeep harness. It was all coiled up nice and neat. The computer threw no codes. So my guess is to simply dump everything I disconnect.

To keep the factory gauges, there are several solutions to the tachometer issues. From an emulator to a setting the GM computer, it can be done. I'll use the Jeep oil pressure and water temp senders in the LS motor to keep those gauges happy.

Having reviewed both GM and Jeep wiring diagrams, I know for sure that you can cut the GM pigtail and splice it in the Jeep harness to make your Jeep computer talk to the LS A/C compressor. Keeping the Jeep high and low pressure switches in place will make the Jeep computer think the LS compressor is the Jeep's original A/C compressor.

The speedo will not be an issue if I keep my NP231J. I might have to swap input housing and shafts from a 231C. But either way, I'll keep my Jeep's factory speedo and wiring components.

I can keep two OBDII ports, but the original Jeep one won't tell me much. The GM will give me engine stuff.

The engine will be mostly 'stand alone'.
 
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You might already know but the ls needs the factory temp sensor to run but it does not need the oil pressure.

so don’t eliminate its sensor when you add the Jeep sender into the head.
 
When I swapped a GM into my TJ, I pulled ALL the chrysler wiring and re-wired with the entire GM car's harness, all the way to the taillights. Not that it's the best idea. Just how I did mine. (pre-LS swap fad). And for what it's worth, there are 'custom' dash kits readily available for swap guys to simply replace the TJ dash with a modern aftermarket dash. I built my own, and it's sweet, but doubt I'd do it again as it's simply too easy to go aftermarket now. If I were OP, I'd get a stand alone LS harness and an aftermarket dash kit.
 
When I swapped a GM into my TJ, I pulled ALL the chrysler wiring and re-wired with the entire GM car's harness, all the way to the taillights. Not that it's the best idea. Just how I did mine. (pre-LS swap fad). And for what it's worth, there are 'custom' dash kits readily available for swap guys to simply replace the TJ dash with a modern aftermarket dash. I built my own, and it's sweet, but doubt I'd do it again as it's simply too easy to go aftermarket now. If I were OP, I'd get a stand alone LS harness and an aftermarket dash kit.

I really appreciate the feedback. It's good to know that you can do an entire wiring swap. I'll bet that was fun. I'm not going to do a stand alone harness because I don't want to pay for something that I can do myself for free. I'm old fashion. I'm a built, not bought type guy. I really enjoy building, not assembling. Sure it'd be easier to buy a kit to simplify things. But I really like the stock look and, again, enjoy the work. I really do find the wiring relaxing. That's why I got wiring diagrams and sorted out much of the wiring.
 
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