Sub Tank Switch Wiring Diagram question

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Romer

Romer

fatherofdaughterofromer
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I have the Toyota OEM Sub tank Switch and Georges ECU. I can see from George's ECU schematic where two connections from the switch go. Can't find the list of switch pinouts or the wiring of the other pins anywhere. Need to define this so I can build the harness connecting the ECU to the switch and the rest of the harness.
 
Here are my notes on it.

“2” 14 Gauge wires from relay to pump ( www.apeusa.com pump gsl391 with 30 amp relay)
Pump Red Positive
Yellow Ground

“3” Wires from sending unit to ECU Kick Panel console. 16 gauge.
White Black = Ground
Yellow Red = Fuel Gage
Yellow Green = Empty / Shut off

White/black
Subtank switch



ECU top right and down.

Sub Tank Switch pin 4 ( Black )
Pos. coil relay (Green) Relay 86 pos coil
Sub tank sending unit empty yellow green from sub tank (Yellow from ECU Black from tank)
Sub Tank Switch pin 9
Sub Tank Switch pin 3 / Ground and Relay 85 neg coil
Sub Tank Switch pin 6

12Volts (white wire from ECU)


Sub Tank Switch
90980-10801 Sub Tank Female Connector


Pin 2 Positive ash tray light (Red) Solid Green
Pin 1 Negative ash tray light (Green) White Green Tracer
Pin 3 Ground and ECU (Green) and Relay 85

Pin 4 ECU (Black)
Pin 6 ECU (Brown) SW1A
Pin 9 ECU pump (Red) SW1B

Rocker Switch for Gauge
Yellow Red DS Kick Panel 22 Pin Connector Pin 18 Gauge sending wire.


4 3 ll 2 1
9 76


Sub Tank Harness Wires
Black Empty ECU
Red Gauge Switch
Green Ground

Relay Coil 85 86
Coil
Positive 12 volts on 30 and 87 goes to pump
Picture.webp
 
excellent, just what I needed on the switch.

Thanks
 
Some conversion please. I am using Georges ECU.

Switch pin4 and pin 3, where do they go? do they just tie together as grounds?

George's ECU has a SW1 transfer light, does this go to the one marked relay on the switch?
 
The cab part of the harness is built. One question on where to route something

Wire 3 from the Sub Tank switch

Kevin's Diagram has this titled Indicator bulb and does not show where it goes.

The above info has this titled "Ground and relay 85"​

What does this hook to?
 
The Indicator bulb in the subtank switch gets +12V from the ECU (split wire or whatever), the other side of the bulb (the orange wire that goes no where in Kevin's drawing) connects to body ground or ECU ground (all the same thing). This lets the Indicator bulb light up whenever 12V is sent to the pump - i.e. a transfer is in progress.

copied from George's instructions to me
 
Romer

Not sure if you have planned to use the factory harness as I mentioned above but I have some additional information.

I opened up the DS kick panel this weekend and found the plug I referred to in post 7 in this thread: https://forum.ih8mud.com/showthread.php?t=140830&highlight=subtankre

The 20 pin plug connects to the main chassis harness at the very front (see pic 2), its a little hard to get to. But the 3 pin female cavities are empty (pic 1), the male pins are present in the floor harness. You can see the empty cavities to the left the green wire on the lower right corner of the plug housing.

So If you want to use this to connect the ECU and gauge to the sending unit it can be done easily. You will need 3 wire repair splices from Dan, PN 82998-12340. These will plug in the housing (pic 1) On the gauge/ecu end you can use a molex (or similar) plug to connect it to the gauge and ecu wires. Since there is a third wire available I am thinking this can be used for the 12v+ for the fuel pump.

Also, I noticed on the ABS harness mentioned in the above thread that some relocation of the wires in the housings will be necessary. This shouldn't be a big deal since the 2 pin ABS plug and the sending unit plug need to be changed. (provided you do not get the factory harness)

I have the factory wire harness repair manual that shows how to remove and replace the pins from/in the housing. I am happy to email you the sections you need to perform any of these operations. They also available at toyota techdoc web site for down load.
Picture 002.webp
Picture 003.webp
 
Thanks for the tip. Can you clarify the below

Cruiser804 said:
But the 3 pin female cavities are empty (pic 1), the male pins are present in the floor harness. You can see the empty cavities to the left the green wire on the lower right corner of the plug housing.

To me that would infer the 3 male pins that are in the floor harness you have traced back to the sender. Not sure though.

I already built my in cab harness terminating at a 9 pin molex connector with 3 pins in it. The other pins have splices on it for connection in the cab to power, ground, light dimming signals, etc.

Pump Power
Tank Empty
Tank Gauge

I was planning on building a 3 wire harness from the other side of the molex all the way back to the tank and then use a 3 pin connector set Dan got me.

Do you see something wrong with this plan.
Click to expand...
Click to expand...
 
I also noticed this plug behind the ash tray. It contains a ground, 12v+ constant and a 12v+ ignition. I haven't done my homework on this on but if I can I plan to use this for my 12 volt ignition and ground for the switch. This will reduce the number of splices necessary.

The housing itself is PN 90980-10997. Dan should be able to get the male housing for this and the repair splices needed to populate the appropriate cavities. Do don't want this PN but the one it mates to.

The cavity on the left bottom corner is 12+ constant (it had power whether the ignition was on or not), the one next to it is 12v+ignition and the ground is top row forth from the left (brown wiring coming into it.) I checked all these with a multimeter. I did not check to see if one of these was connected to the dimmer for the lights. Didn't think of it until I have everything back together. And I am not really sure what to look for.

Turns out this is one of three plugs for various radio options. There is also another plug hidden behind the radio. These 2 together have all the speaker connections, a 12v ACC, ground and both sides needed to add another dash light e.g. for the subtank switch. Bummer is, the white/green for the rheostat is in the 6 cavity plug and the green from the 10A dome 12v is in the 10 cavity plug.


I think I remember a post on the purpose of this plug somewhere. I plan to look for it and post it here.
Picture 001.webp
 
Last edited:
You may have missed my post above as it came between yours.

Another piece of info is that I am not putting my switch where you are as my slots are all filled. I will be putting it over on the left side so I will take the power I need off of the fuse box.

I could do this by reading the wiring diagram, but have you isolated the existing fuel sender line to splice the switch into?
 
Romer said:
Thanks for the tip. Can you clarify the below

Cruiser804 said:
But the 3 pin female cavities are empty (pic 1), the male pins are present in the floor harness. You can see the empty cavities to the left the green wire on the lower right corner of the plug housing.

The housings are populated by wires attached to male or female pins. Toyota sells repair splices which have a length of wire with a pin (male or female) attached. In this particular connection the floor harness side has the male pins, the chassis side does not have the opposite females, you can get the repair splices with the appropriate pins (female in this case) and insert them and connected them to your wires via molex plug to the wires that you want to travel to the rear.



To me that would infer the 3 male pins that are in the floor harness you have traced back to the sender. Not sure though.

Yes, they go all the way back to the gray plug on the sill harness mentioned in the post link to above. I verified with a continuity meter. I have a spare floor, sill and ABS harness which made it easy> :)


I already built my in cab harness terminating at a 9 pin molex connector with 3 pins in it. The other pins have splices on it for connection in the cab to power, ground, light dimming signals, etc.

Pump Power
Tank Empty
Tank Gauge

That will work. I think this is how George and Kevin did it.


I was planning on building a 3 wire harness from the other side of the molex all the way back to the tank and then use a 3 pin connector set Dan got me.

This is the part that is already present beginning with 20 pin housing in the DS kick panel and end with the gray plug on the sill harness




Do you see something wrong with this plan.
Click to expand...

Not great a using quote tool. Hope you can figure out my answers
Click to expand...
Click to expand...
 
Romer said:
You may have missed my post above as it came between yours.

Another piece of info is that I am not putting my switch where you are as my slots are all filled. I will be putting it over on the left side so I will take the power I need off of the fuse box.

I could do this by reading the wiring diagram, but have you isolated the existing fuel sender line to splice the switch into?
Click to expand...

No need to splice to get to the sending unit. I plan to call Dan to discuss and order the parts I need.
 
is it possible to splice in sections of wire to the ABS harness where the stuff runs along the frame near the wheel?



Cruiser804 said:
Romer

Not sure if you have planned to use the factory harness as I mentioned above but I have some additional information.

I opened up the DS kick panel this weekend and found the plug I referred to in post 7 in this thread: https://forum.ih8mud.com/showthread.php?t=140830&highlight=subtankre

The 20 pin plug connects to the main chassis harness at the very front (see pic 2), its a little hard to get to. But the 3 pin female cavities are empty (pic 1), the male pins are present in the floor harness. You can see the empty cavities to the left the green wire on the lower right corner of the plug housing.

So If you want to use this to connect the ECU and gauge to the sending unit it can be done easily. You will need 3 wire repair splices from Dan, PN 82998-12340. These will plug in the housing (pic 1) On the gauge/ecu end you can use a molex (or similar) plug to connect it to the gauge and ecu wires. Since there is a third wire available I am thinking this can be used for the 12v+ for the fuel pump.

Also, I noticed on the ABS harness mentioned in the above thread that some relocation of the wires in the housings will be necessary. This shouldn't be a big deal since the 2 pin ABS plug and the sending unit plug need to be changed. (provided you do not get the factory harness)

I have the factory wire harness repair manual that shows how to remove and replace the pins from/in the housing. I am happy to email you the sections you need to perform any of these operations. They also available at toyota techdoc web site for down load.
Click to expand...
 
FYI

I was trying to do the install using the existing harness and ran into some problems. My LX450 does not have the white plug behind the drivers side sill. Also the 3 plugs on the frontmost plug are occupied, WTF. :mad:

I can tell you that the subtank harness originally connected to the main tank harness and plugged into the white plug behind the drivers sill. The wire gauge for the subtank pump is not as heavy as for the main tank so I believe the gauge of the 3 open wires that go to the DS kickpanel as described is probably sufficient. If my three were open thats the way I would have wired it.

chris
 
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