purchased this truck for my son last year before knowing about the fuel gage issues. i want to find a wiring diagram for the sending unit so i will know which wire goes to the unit and which one is a return to ground. i have access to a potentiometer i want to want to wire in. i plan on cutting these two wires, splicing in the pot and setting it to different resistances that match full,half full,etc while still being able to drive the truck. this way if i leave on half full a few days and gage stays on half full i will know its the sending unit or a ground to the unit. if gage is still not dependable i will know its in the gage and most likely not worth the cost of repair.i wish previous owner had this fixed under the tsb but now its my problem. if you have wiring diagram or a link please let me know. autozone and chiltons dont have this in their diagrams.

no grounds.

here you go

everything i read has said to measure resistance between #2 & #3 pins on plug which would be y-r and br-b with no mention of #1 orange wire. do you know what part it plays in circuit? i see this circuit has no ground. i had thought it read resistance to ground but no matter as long as i know which wires to use.

I would unplug the electrical connector under the rear seat. I would jump the Yellow /red and the orange and see if the gauge moves. I would then jump those wires with the brown/black wire and see if the gauge moves.

Keep in mind that the gauge does react slowly.

If the gauge moves, then the sending unit is bad and viceversa if nothing happens, then the instrument cluster is bad.

i have been trying to find that connector location or the one at left kick panel w/ 20 pins

found connector under seat and cut y-r that goes to pin #2 and br-b to pin #3. wired in my resistor and increased and decreased resistance 12 ohm to 184 ohms which should be empty to full and gage does not move. its on empty where it mostly stays on full when hooked up.. reading troubleshooting guides say to put a 3.4 watt bulb in line at it should light up and gage raise to full. i put my meter across wires and i have less than 1 volt so even if i tried this there is no power to turn on bulb.also to check low level light connect #3(br-b) to neg battery terminal and positive to the 3.4watt light and then to #1(orange). if tank empty light will come on in a few seconds if full light wont come on. i have wires cut and no power at all to sending unit but still have a low level light.next i reconnected all wires. fuel gage went to full and low level light went off. i disconnected orange wire and gage slowly dropped and low level light came on about when it should have.if orange is low level how is light working correctly? reconnected orange and diconnected brown, gage stayed on full. reconnected brown and disconnected y-r and gage slowly dropped with low level light coming on correctly.

Google translate please.

Did you follow my directions in post 4?

If the gauge works when you manipulate the signal then your fuel sender is bad.

i never put all three together. i understand orange is the low level light. next opportunity i will try some more things. i may not have had enough patience when adjusting the pot i put in as i was expecting movement each time i adjusted resistance immediately. its very puzzling that if the orange is the low level how the light would come on anyway just before the gage hit the empty mark

I didn't ever say to tie all three together. One set at a time.

If the Gauge moves and the light comes on and off, the the sender is bad.

truck is gone for the weekend. after a little thought if i tie y-r and br-b together that will be no resistance at all. gage should be on "E" with 12 ohms so with zero it will not move. if y-r is supposed to have 5 volts and the sending unit is 12 -194 ohms then less voltage should make it read full and more voltage read empty. in a DC circuit you get a voltage drop across resistance. so the higher the resistance the more voltage drop. interested in knowing if y-r is positive voltage thru sending unit to gauge and the other side of gauge is ground. also interested in if y-r is positive to lowfuel light how i still got a low fuel light with orange disconnected

I don't remember what the orange wire is.

Here is an interesting tidbit. I did a swap a couple years ago and during that time, I retrofitted a Sequoia gauge cluster in my 4runner.

Long story made short, My fuel gauge was malfunctioning from the swap. When the tank was full, it read empty and had the low fuel light on in the dash and when the tank was empty, it showed the gauge being full and the light off.

I had to turn my fuel sender up side down to get it to read right. Problem solved.



You are making a mountain out of an ant hill.

Does the gauge work when you manipulate the signal (touch the wires together)? If it does then the fuel sender is bad.

If it doesn't then the gauge is bad or less likely one of the wires from the sender to the gauge is bad.

i have found all other toyotas are empty high resistance and full low resistance just the opposite of 4runners. as i stated if low resistance(12ohms) is empty and 184ohms full then no resistance will go from off and gauge showing empty to on and gauge showing empty.

FSM testing procedure is on pp BE-51 & 52 here:

http://tacoma.site40.net/4Runner_96-...ommet/insp.pdf

if a 99 is the same this really helps. i can see positive thru fuel gage first which will drop the voltage maybe (even to the 5 volts i had read somewhere else) then thru the sending unit to ground. when the sending unit changes resistance it will also change voltage at gauge. hope i get a chance monday

rainy,cold here in nc so i did not spend a lot of time on it. i tested voltage between y-r and bl-b and go nothing. tested between y-r and a good ground and got 4.8 vdc. tested continuity between bl-b and same ground point and got no connection. this told me bl-b back to combination meter has lost ground somewhere. since i had already cut and spliced wires last week i wired in another ground and tied into bl-b. gauge is now reading about 3/4 tank with 56 miles since last fill-up. will have him watch gauge and hopefully problem is solved. will post results later. thanks to everyone