Oem sub tank wiring LX450

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Mar 12, 2012
Mission Viejo
I am bringing in a complete sub tank system from AU and need to know what harness sections I need to add to my LX450. I don't have the fuel ecu connector above the DS wheel well. I have a 94 fuel ecu coming and a complete sub tank system including overhead console with wiring from a 96 LC that the seller is swapping to diesel. He's offering to sell me his entire harness but before I do that I want to know if it would be better to find a 94 or older AU spec, sub tank equipped harness instead. I know the 80s here in the US had some of the wiring for the sub tank system but not all of it and according to other posts the LX has none of it. Should it be difficult to combine my LX450 harness with the <94 AU sub tank equipped harness? Since I am bringing in all oem parts I would like to make the wiring as clean and stock as possible. If I can't find a <95 sub tank equipped harness before it's time to ship my parts my plan B is to first add the missing parts to make my LX have the same harness as the US 80 by scavenging a US 80 harness, and then modify the wiring as shown in many of the posts. Not sure which plan is better? I know this has been done before so I hope someone has the answer
Ok, I have studied your install and it has a ton of good info. I was able to get a 94 fuel ECU from AU before I realized my LX didn't have the connector in the rear quarter panel. I also bought a main tank from a sub tank equipped truck so I have the float switch and harness extension that connect to the sub and main tanks but I don't see an unused connector under the body in mine to connect it to but then again I don't know exactly where it should be. I do have one unused connector on the underside/center of the rear crossmember. Even if I don't have this wiring in the rear do I have connectors in the kick panel that that just need pins/wires added to them? I also got an overhead console with the harness that runs down the A pillar to the kick panel. The only other portion I'm confused about is the wiring I may not have for the switch. I bought a transfer switch that has 7 pins on it but not the connector that mates to it.
Based on my experience with my 96 LC, and helping to sort a few other installs, I would recommend building a dedicated separate wiring loom for your LX. As you have found out, most if not all of the OEM wiring is not in the Lexus loom. Easier in my view.


I don't mind putting together a separate harness but I still need to find the 20 pin connector for the fuel ECU to do it.
My sub tank got rejected for SeaMail for being oversize by 5cm, not sure how everyone else got it through, so I am going the Sea Freight route and it's one price for up to a cubic meter of cargo. I added in a main tank and pretty much everything else for the install from a 96 going to diesel. I worked out a deal with a pack and ship place in Victoria so that I could send items I find to them and they will box it all up and send it out since most AU ebay/gumtree sellers won't ship to the States for some reason. The only other item I know I don't have is the connector for the fuel transfer switch. Tried emailing the parts department of a AU Toyota dealer to check availability but never got a response.
Sub tank parts finally arrived

Today I picked up my sea freight shipment with the parts for my sub tank install. Ended up buying 2 transfer pump/solenoid assemblies to have a spare and a second main tank pump bracket assembly from a sub tank equipped 80 in case the one in the main tank I bought was toast. The sub tank doesn't look like it has ever even had gas in it and is perfect inside. Sub tank has a small ding in the top but no puncture so I'm just going to leave it be. Not sure if it happened in shipping or not. Found a tan console and even got the harness section that runs from the console down to the kick panel. Now I just need some free time to start swapping parts...
Pile of parts

Here's what I have

Congratulations. That sub tank looks new. I just finished mine a few weeks ago although I went with George's ecu.
Nice score on the tan overhead console !!

Call ' em back, and ask 'em to run back into the yard, and grab the sun visors !!

Remember you don't necessarily need the big 20(?) pin connector for the ECU. It's not the end of the world to plug the wires one at a time into the ECU. The plug just makes it quick & easy.
I found some visors in England that look brand new as well. Most of the Aussie ones are pretty beat up. Apparently 80s in the UK had the console option but it just has a compass and altimeter. Trying to get a shipping quote but I don't think it will be too bad. I am going to try using the stock ECU but George's is a good plan B.
George's ECU is simple and robust. Mine has been in trouble-free service for several years.
Great score as it looks like you have everything to do the OEM setup, including the main tank. As noted earlier, you will need to build a custom harness. If you do go the George ECU route, I am sure there are a few folks here who will buy the unused parts.


I have finally started the process of installing my sub tank. Following the advise of others I'm starting with the electrical and I need some help with the sub tank sender. I was able to get a complete driver side harness today from a 94 which solves the problem of my LX not having the connector for the fuel ecu in the rear quarter panel. One hurdle cleared... The only connection I don't have now is the 3 pin triangular connector for the sub tank sender. In looking at the install pics of others and reading the write ups the connector should be there but the only unused connector I have in the rear crossmember area is a 6 pin gray connector in the middle of rear body shown in the pic above. The item in the foreground is the socket for lowering the spare( left is towards the rear of the truck). My question is does a harness plug into that 6 pin connector which has the plug for the sub tank sender or is this another instance of the LX not having the necessary wiring. Does anyone with a LC have a triangular 3 pin unused connector hanging in the rear crossmember area? The sub tank has a cable clip that routes the sender wire towards the rear of the truck so the connector would be close to centerline of the truck I believe.
There should be a short cable (that came with the subtank) that goes between the subtank connector and the connector in your picture.

Refer to my install -> http://www.george4wd.taskled.com/auxtank.html and you'll see a picture of the painted subtank with the short cable that mates to the connector in your picture.

Thanks George for the info, I didn't get that complete section of harness with the tank, but I did get the 3 pin end with about 3 inches of wire. Why they cut it off instead of just unplugging it from the 6 pin connector I don't know but at least I have one end of it. So most importantly, the six pin connector hanging in my truck does have the wires I need running up the the driver's kick panel? Now I just need to either find that harness somehow or just buy the mating connector shell/pins for the 6 pin and build my own using the cutoff connector I have. I'm going start disassembling the donor harness I got yesterday and extract what I need for the fuel ECU and then pull my harness. Just out of curiosity why does the connector have 6 pins when the sub tank sender only needs 3 wires? Is there something else in that short harness section?
Nothing else on that connector that I know of. Just a standard connector that toyota decided to use. Wouldn't be the first connector that has some empty/unused pins...

I went with my own wiring and my own transfer pump controller/ecu. Seemed way too much work and headache to try and source all the original electrical stuff. Good luck.

With the help of the parts counter guy at Toyota I was able to order the connector shell/pins for the 6 pin connector so I can create my own "Wire, Frame no.3" so I think I have everything I need to get started.
Transfer pump bracket is re-plated, now onto powder coating solenoid mount and main bracket.
Pump Bracket Before.JPG
Pump Bracket After.JPG

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