Gauges and the wiring harness

I plan on doing a 4.3L to 5.7L LS1

What I seem to not understand about the swaps (looking through a few here) is the gauges. How does the stock cluster work if you were to order an aftermarket wiring harness? For example, I have an EFI CONNECTION wiring harness from my last v8 swap, all the harness did was control the engine/trans (it had it's own pcm, did not come with wiring for any emissions/rear o2s) which meant I was not able to use any gauges unless they were aftermarket

My guess is that I will HAVE to buy a stock 5.3L engine harness/pcm and have it flashed somewhat to work with the LS1. Which would seem to also allow the stock gauge cluster in the Silverado to work. So buying a full 5.3L harness and replacing the 4.6L harness with it, would pretty much allow me to throw the ls1 in there and plug everything up and be 100% ready to go


also, seems a lot of people on the site refer to an LS1 as the 5.7 AND 5.3L, it is somewhat confusing - but can I consider the 2 EXACTLY the same as far as major parts (like wiring/mounting)

What is the truck you're doing the swap in?

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Originally Posted by TTU713

I plan on doing a 4.3L to 5.7L LS1

What I seem to not understand about the swaps (looking through a few here) is the gauges. How does the stock cluster work if you were to order an aftermarket wiring harness? For example, I have an EFI CONNECTION wiring harness from my last v8 swap, all the harness did was control the engine/trans (it had it's own pcm, did not come with wiring for any emissions/rear o2s) which meant I was not able to use any gauges unless they were aftermarket

My guess is that I will HAVE to buy a stock 5.3L engine harness/pcm and have it flashed somewhat to work with the LS1. Which would seem to also allow the stock gauge cluster in the Silverado to work. So buying a full 5.3L harness and replacing the 4.6L harness with it, would pretty much allow me to throw the ls1 in there and plug everything up and be 100% ready to go


also, seems a lot of people on the site refer to an LS1 as the 5.7 AND 5.3L, it is somewhat confusing - but can I consider the 2 EXACTLY the same as far as major parts (like wiring/mounting)

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We usually refer to the swap as an LS swap regardless of motor. They are the LS series, based off the LS1. 4.8, 5.3, 5.7, 6.0, and 6.2 are all LS motors. The swaps are the exact same other than the intake and TB.

Yeah, need to know what vehicle(truck?) you have. But, when installing an LS1 engine, I'd use the original engine harness that came on that year engine. Modify it, by sending it out, or doing it yourself, into a stand-alone harness. Wire it in, to your own vehicle, and start it up. Go with the original 0411 computer as well. It will have to be reflashed(reprogrammed) to delete the VATS system(vehicle anti-theft system), delete the two rear O2(oxygen) sensors, programmed for your rear end gear ratio & tire size, etc. To start it up, install the harness to two 12 volt power wires, hook up the gas, and it will start right up & run. Have to know what vehicle you have, to answer your gauge questions.

it would be the newer body style silverado, I haven't bought one yet. I'm actually trying to decide from either buying a older style silverado (year 2000) w/ the 5.3L or buying a newer body style silverado w/ a V6 and swapping in the LS1

Pl4yboy, thanks for the response. It will help out when I am researching knowing that the only difference is the TB and intake

I already have an aftermarket harness/pcm from www.eficonnection.com that works with the engine. The only thing I see a problem is getting the guages to work since the wires go from the battery to the pcm to the engine (and no where else)

If you're buying a 99+ just use a harness from a 99+ V8 truck. Save yourself a massive hassle. 99-02 use the same, 03-07 Classic (05-07 have provisions for electric fans) use the same. The PCM in the v6 trucks are the same, just need the harness and all your other typcal swap stuff, mounts, hoses, accesories etc.

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Originally Posted by Frenchy

If you're buying a 99+ just use a harness from a 99+ V8 truck. Save yourself a massive hassle. 99-02 use the same, 03-07 Classic (05-07 have provisions for electric fans) use the same. The PCM in the v6 trucks are the same, just need the harness and all your other typcal swap stuff, mounts, hoses, accesories etc.

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x2 sell your aftermarket stand alone harnness, a factory harrness from the year truck you have (and not the motor) will just plug and play into the truck, everything will work factory.

awesome thanks, that is what I read in one of the main V6 to V8 swap threads, just wanted to make sure it wouldn't be a good idea to use my stand alone harness

so to make sure I 100% understand lol, if I were to by a 2005 V6 silverado and wanted to put in my 2000 model LS1 in it, I would just purchase any wiring harness for a V8 silverado year 1999+ (Kind of confused with the other years you added on there, is this correct or would I need to buy v8 harness off a 03-07 depending on electric fan or not)

IMO if your going to buy a V6 truck with the intent of doing a swap, do it with a 99-02. In 2003 the V8 trucks switched to a drive by wire setup, the V6 trucks didn't. It's not a huge deal to convert to DBW in the 03+ but it's just that extra bit more. But yes if you were going to buy an '05 get a harness from an 05-07 Classic (NNBS trucks are completely different, if you get parts from an 07 make sure it looks like an 06).