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hey need some help from you guys. doin a ls1/4l60e into a 03 is300. need a little bit of help with wiring. i know the LS stuff up and down but need some help wiring it to the lexus stuff and making the gauges, fans etc to work as one. at the moment i have a 99 5.3l harness that i need to break down. i was goin to buy the Dedicated harness but i heard it work more for t56 and not the auto as much.
Fans will work even with the Lexus ECU removed, or you can wire them into the LS PCM if you want to change the temps they come on. To keep the coolant temp gauge working you need to keep the Lexus ECU hooked up and install a second temp sensor in the opposite head. You can wire it direct since the resistance range is the same between GM and Lexus. If you keep the Lexus ECU and put the stock MAF inline with the new intake your gas gauge should work correctly. If you don't have the ECU or MAF hooked up it will only pulse off the float and the gauge will drop at 1/4 tank increments.
I wired my car myself including stripping down an F-body harness so I don't know anything about the dedicated motorsports harness. I do know that Matt is a very talented guy and has been very helpful in the past for me.
As in Lexus ecu, are you talking about the engine ecu or the one inside the car? When you say to get another reno gauge and write it direct, dip you mean direct to the gauge cluster? Sorry haven't done a swap into this new of a car. Did you run a sprays fuse block for the LS harness or tie into the Lexus one? I see allot of guys tie into the Lexus one. I did buy a factory electrical manual for the Lexus to help me a little.
The Lexus ECU I was speaking of is the one under the hood (behind the drivers headlinght). The second temp sensor gets wired to the Lexus ECU in place of the original temp sensor, two wires.
I tied all my fused leads into the lexus fuse block. I'm rebuilding the car right now (catastrophic wreck) and plan to use a dedicated fuse block to clean things up and make maintenace/troubleshooting easier.
hmm all the builds i see in these cars i havent seen anyone keep the stock ecu. interesting.
couldnt you use the 3 wire temp sensor and just have that one in the drivers head like usual?
i pm'd Matt last night asking him a couple things about his stuff. dunno how often he comes on here though.
right now im just throwing my car all together and then go through it later on. after i get it fired up its goin to my buddies shop for him to make me a custom aluminum exhaust, cold air intake and abs module relocation.
The LS ECU needs to see a temp sensor as well. I installed a second sensor, driver side wired to the Lexus ECU, passenger side wired to the LS ECU. I was thinking it was 2 wire, but could have been 3 wire. It was just the standard F-body temp sensor.
I'm definately in the minority of swaps that kept the Lexus ECU, but I wanted to keep as many things working as possible. Here is my old build thread for more information.
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lsx is300 guys 
