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o2 sensor wiring

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Old 11-24-2009, 10:56 AM   #1
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o2 sensor wiring

I've searched a ton. Theres lots of info out there on sensor wiring. But i cant find anything for the truck wiring. My truck is a 90 4 runner with a 22re. It has a 4 wire o2 sensor.

the wires on the sensor are the typical :
Blue (signal +)
white (signal -)
black (heater)
black (heater)

I need help figuring out what those wires should hook up to on the truck side. The oem plug is long gone and the wires have been butt connected together. But i dont think the previous owner hooked them up right.

wire colours on the truck are as follows.
black and double insulated. i assume this is the sensor (+)
white w/ red stripe
pink or brown w/ green stripe.

Thanks for your help.
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Old 11-25-2009, 06:46 PM   #2
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well i did some diagnosing. one of the heater circuit wires was hooked up to a "sensor signal" wire. anyways i fixed that. still same code. so i replaced the o2 sensor with a new ngk sensor. same problem.

code 21. I cleared the codes ( unhooked batt for 5min) and before i even started it i checked and code 21 was still there . whats wierd is. sometimes as soon as i start the truck, the c.e.l comes on. other times it stays off until i give it some throttle. Its also started to bog down on acceleration.

any ideas??
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Old 11-26-2009, 04:54 PM   #3
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seems like im talking to myself here....... do i smell or somethin? lol

anyways got some more work done today. changed the spark plugs and put in a computer from a 87 p/u. CEL is now off and thing drives great. exhuast still smells a little rich. But the cat is hollow. I have go get "aircared" as we call it up here. I have anew cat to put on. hopefully she passes.

Anyone know the differences between computers? The plugs on the computer were a different colour. the 87 had yellow plugs the 90 has grey. also the 87 only had a single wire o2 sensor. the 90 has a 4 wire sensor. I'm gonna look for a good used one of the proper year. But so far seems to work good.
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Old 11-26-2009, 06:01 PM   #4
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just so you're not hearing an echo for three days, i'll chime in. i just changed a 4wire ox on my 88. white/blue/2 black. but my harness was under the seat, a 4 pin yellow, so i was able to trace and cut in the new one. (the new one had a short plug)

as you mentioned, an 87 is single wire Ox, and much more basic emission controls. your truck may have TWO Ox sensors. i don't think you can use an 87 computer in a 90. check out the diagrams in this link. i glanced and saw one of the wires on the main Ox was pink/green as you mentioned. hope this helps.

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Old 11-26-2009, 06:27 PM   #5
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The FSM here: http://www.ncttora.com/fsm/index.html and labeled 90-95 4Runner (shows a red 4Runner) has an electrical manual for the 3vz. In the "engine control", 3VZ section, page 62, is the wiring diagram for the oxygen sensors.

I would be interested in seeing if the aircare passes you with the incorrect year ECM installed. Let us know what happens.
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Old 11-26-2009, 07:44 PM   #6
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Took me about 5 minutes to search:


Pin 1; Pnk-Grn, ECU controlled ground for heater element
Pin 2; Red-Wht, ECU supplied B+
Pin 3; Black, Oxygen sensor output in millivolts. Can be measured in Diagnostic connector (pin 4, marked Ox)
Pin 4; Brown, Ground
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Old 11-27-2009, 05:01 PM   #7
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thanks for the input guys. I plan on finding the proper computer for it on monday. I just needed to get it running properly and changing the computer seemed to do the trick for now.

Thanks for the links too. I tried searching, but i guess if you dont put the proper keywords in, it can take awhile.
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Old 11-21-2011, 05:10 PM   #8
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I wouldn't run that 87 ecu in it for too long. 85-(mid) 88 efi engines run low resistance fuel injectors that require a resistor pack to lower the ohm reading to 3.5 ohms. Later models have high resistance injectors (13.5 ohms) and do not require the resistor pack. Although your truck may have run ok with the 87 ecu, it would probably end up burning out the injector driver circuitry, rendering the ecu inoperable.
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22re, 90, acceleration, bogs, canada, diagram, heater, o2, oxigen, oxygen, runner, sensor, sensors, wir, wire

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