RMcQ

You might rember me as the n00b that showed up a few months ago asking about whether I should buy this truck for $1000. I ended up buying it for $750! Some of the best fun/$ I have spent in a while.



Well, I had some things to patch up to get it on the road, but about $400 later I'm feeling pretty good about the mechanicals. Even took a 300+ mile road trip to the OBX no problem.



Anyway - I have had an intermittant check engine light which I didn't stress about but I do have to get the truck through emissions testing next month so I decided to check out the oxygen sensor and probably replace it. Low and behold the sensor is not attached to anything. It has a 8" of wiring and a connector on it which was just tucked under a protective plate under the truck. I figured the wiring passed through the body under this plate, but when I removed it there is nothing. I can't figure out where the sensor should be plugged in. There is no wiring anywhere near the oxygen sensor.

Perhaps it was removed by a previous owner? If so, where do I start under teh hood to get this patched back together? Or is there something I am missing about where the wiring is hiding?

I need to figure this out in the next week or so. Thanks for any input.

RMcQ

I found a connector coming out of the main ECU wiring harness located under the intake manifold with nothing connected to it. There are 2 wires - black and black/white stripe.

The o2 sensor is only a one wire sensor.

Am I on to anything here?

RMcQ

Did I forget to say please? I'm sure somebody has a wiring diagram for an '88 4Runner. What colors are coming out of the ECU wiring harness heading to the O2 sensor? Is there supposed to be a plug beneath the intake manifold that leads on back to the o2 sensor? Was it originally set up as a 1 wire sensor or did some hack PO put the wrong thing in.

Please I need a little help here.

RuffRider

I could look at my '99 Runner but I suspect the wiring will be different. It would be great if there were online wiring schematics...

Let me know and I'll take a look when I get home.

Flamedx4

Good replies in your other (duplicate) thread...
Never heard of a one wire o2 sensor. They need multiple wires.

NorCalVP

The 02 sensor on my 84 Tercel only has 1 wire...

Sorry can't help on the 4Runner prob...

RMcQ

I posted a duplicate thread to get right to the point and hopefully get some better responses. It worked. This thread has pics and other distractions.

A 1 wire sensor was normal in the early days of emmissions crap. It is grounded to the exhaust to form its circuit. I just need to figure out where to attach this one wire as my truck is missing a whole run of wiring obviously.

MTL_4runner

Yes, you are correct.......the newer sensors have more wires because they are preheated (unheated sensors are not very relaible to the ECU if they cool to under 600 degrees while in use). The old style as you have just produces a signal voltage.

You'll need to get a wiring diagram for that vehicle to find what color it connects to at the ECU and then trace it back to the sensor location.

Fahrenheit 451

V6 or 4cyl? On the 22re, the o2 sensor plugs into the harness on the driver's side fender near the ignitor. It goes into the same harness that the wires from the master cylinder reservoir are in.
I have pics if you need them.

RMcQ

Thank you. I got some info from forum member WaskillyWabbit that pointed me in the same direction. I found the empty yellow single wire plug on the drivers side fender. This is what I was looking for. Thanks again.

rustyrunnerboy

So I have the same problem, the o2 sensor is just there, it doesn't even have wires coming out of it...not that that makes a difference if its not connected anyway. But i'm wondering what effect this would have on the engine? wrong mixure, bad mileage, long term damage?anything good or bad about it not being connected...and did something have to be bypassed to get the motor to run w/out the o2 sensor. I've got a 1989 4runner 22re 2.4L straight 4...

Nam

Not only it will not pass smog inspection, poor MPG, and whole bunch of other things e.g. if the engine produces too much unburn gas, it could damage the Catalytic converter...

Just get another sensor and connect it to the wiring harness.

Nam

rustyrunnerboy

ok, so i got a sensor from someone who totalled his 1987 runner...It should be the same right? Anyway, i get in there and i look for the place to connect the sensor to the wiring harness, but I see none, could someone post a picture up of what it looks like on a 1989 22re efi...or something just the same. I can't find any empty connections...picture would be very very helpful... While I was in there I also found that there were two wires disconnected from the intake area...looked around, but icant see what they might connect to...any ideas...i think the previous owner changed engines...
Drew

pcola

i have a 88 pickup (22re) and i only have one o2 sensor. it hass 4 wires and goes threw a grommet located right under driver side seat. i removed bottom trim so i could look under the carpet and found it plugs into a round connector. i have also read that they should be replaced every 30,000 miles?? but the bolts holding mine into the exhaust pipe are rusted so bad im just going to unplug and weld in a new o2 connector. wow got off track lol but i also had a ? since its about the same thing, i have 4 wires 1blue,1white,and 2black.... then on truck harness side wire colors are not the same just wondering if anyone knew what wire is what???