BMC

I have an 87 4runner with a single wire 02 sensor and i want want to replace it with a heated sensor. What is the difference between a 2 wire 3 wire or 4 wire and how do i go about hooking it up.

Thanks Bryan

myyota

Why would you want to chenge the 02 sensor from the single wire to a three wire heated 02 sensor ?. Your not going to gain anything from it.

abecedarian

the main reason for the heated sensors was because they were placed farther away from the cylinders and thus didn't heat up as quick as one right next to the head. and the reason for placing it farther away from the head was so that it would have a more accurate sample of all the cylinders' emissions, mixed together.
now, if yours came with an O2 on the manifold next tothe head, and you put a header in which moved the O2 down below the cab, I can see that.

BMC

Abecedatian that is exactly why im puting a heated sensor In. The check engine light goes on and off while driving because my lce header relocated the sensor and its not staying hot enough to get a correct reading and it wont pass smog. So if anyone can help me with what sensor I need and what I need to do to install it that would be great.

scope103

Ah, yes. All that money on a fancy header, and you can't legally drive it.

Obviously, the easy fix is to put the correct exhaust back in. Somehow I don't think you're interested in that way ...

A heated O2 sensor gets 12v through the two heater pins (easy to tell; they should have 5-7 ohms between them. The others should be open (infinite) between them all.) The ground wire (probably brown, and possibly connected to the case of the sensor) goes to ground (your one-wire sensor grounds through the exhaust pipe, as if that would ever work long-term), and the sensor wire should work connected to your existing sensor wire. The heater is powered through the EFI relay and grounded through the ECM, but I think the ECM is only checking for current flow. You can probably just leave 12v on the heater circuit whenever the ignition is on.

Since you're not likely to find the correct truck-side connector for a heated O2 sensor, you might as well get a "universal" (pig-tailed) sensor and make your own four-pole connector.

Good luck!

abecedarian

For simplicity, a 3 wire O2 should be used. If the exhaust support at the bell housing is installed, and it should be to help keep the manifold nuts from loosening or breaking studs, the signal will have a good ground reference.

The wiring is fairly simple- the signal wire connects to his existing wire and the heater wires will go to a switched 12v source and ground; the heater for the idle air valve is a decent source since it's only on with the key.

trey350

I am in the same boat with my LCE header on my 85 Pickup (22RE). I spoke with the guys at LCE and they said this is an issue with 1 in 100 engines. The four wire O2 sensor was their recommended fix.

The 4 wire O2 sensor has one power wire for the heater wire, one power wire for the signal generated by the O2 sensor, and two ground wires (one for each power wire).

The key info needed for the install is:

• Where to start the power wire for the heater wire.

• What brand and model of four wire O2 sensor will fit the 22RE configuration

Abecedarian's answer to the first question seems good. Some info with regards to a typical location for the idle air valve would be helpful though.

Thanks

abecedarian

The idle air valve is located under the throttle body on the 88 and under 22RE's. It has two air hoses and two coolant hoses connected to it. I suggest this connection because it is under the hood, is switched and not connected to other sensors or components which may be sensitive to voltage like the TPS, VAFM or igniter or distributor. It should have a two wire electrical plug resembling the fuel injector plugs on it- one wire is 12v and the other is ground.

LCE's comment that there are two "power" wires on a 4 wire O2 is incorrect. Whether 3 or 4-wire, such an O2 only requires 1 power source, and that is for the heater circuit. The heater circuit has it's own ground wire.
A 4 wire sensor has two O2 signal wires, neither of which are "power" per se: one wire is the output from the O2 sensor to the ECU and the other is a ground from the ECU so that there is a more accurate signal at the ECU. If you've ever done stereo wiring you would understand the importance of minimizing ground loops, where resistance at various ground locations can result in voltage on a ground wire and thus cause noise and poor quality of the signals.

If a 4 wire sensor is used, the signal ground must be grounded at the ECU.

Now, how do you determine which of the 2 signal wires is ground? The easiest way is to install the O2, fire the engine up and use a high-z voltmeter to measure the output voltage between the two wires from the O2. If the red meter lead is hooked to one wire and the black meter lead is hooked to the other, and the voltage reads positive, the O2 wire the red meter lead on is the one to connect to the ECU and the other is the one to ground; if the readings are negative volts, the O2 wire the black lead is connected to is the signal and the O2 wire the red lead is connected to is the ground.

If you ask can the ground really be that important, keep in mind the ECU expects 0.5v to be the average voltage reported by the O2. If the volts go above 0.5, the ECU leans the mixture and if it goes below, the ECU richens the mixture, and generally stays centered around 0.5 volts from the O2.
Now consider a narrow band O2 sensor should generate between 0.2 and 0.8 volts typically. If there's a poor ground for the O2, the loss due to the poor ground can reduce the O2 output to 0.1-0.7, or even 0.0-0.6.

See where this is going?

If the signal from the O2 doesn't match what the ECU expects, it will attempt to adjust for it. If the O2 stays below 0.5 volts more than it's above 0.5 volts, or above 0.5 more than it's below 0.5, the ECU tries to adapt with what's called "trim", which is a coarse adjustment to the fuel mixture designed as a long term compensation for issues. If the ECU still cannot manage to "trim" the fuel mixture for a 50/50 ratio around 0.5v, it will throw a code... despite the ratio being correct, and all because of a poor ground.


But I suppose one could also wrap the header up to and including the O2 sensor to keep heat in for a 1 wire.

BMC

Thanks for all the help guys. You know abecedarian i was thinking of wraping the header down to the 02 sensor in some header wrap. Its worth a shot. I think im going to try that before i buy another sensor for this thing.

Hey trey i called the guys at LCE over 4 years ago with this problem and they acted like they have never heard anyone with this problem. I then replaced my 02 sensor hoping that would solve my problem and it didnt. So i have just lived with it untill about a month ago when i needed to get it smoged and the check engine light came on. I then had the 02 sensor bung move towards the motor about 18 inches hoping that would take care of it. Nope, I then replaced the oxygen sensor with an oe one. Nope, then i got ride of my high flow cat and put my stock one back on. Nope, i still have the same problem. Im so sick of this header i wish i would never installed it and the people at LCE have been absolutely no help. Im really close to getting a stock manifold and replacing it all back to stock.

abecedarian

Wrap may be worth the try, if the smog people will let you get away with it.
But the real, honest solution would be putting in a heated O2, whether 3 or 4 wire.

Up to you.

BMC

Yeah i think i might just give the wrap a shot. Of course if that doesnt work ill have to replace the sensor for a heated one.

trey350

Thanks for the write up abecedarian. It was a huge help. I followed your instructions precisely and I seem to have a functioning O2 sensor now. Only problem is that the reading on the O2 sensor is on the rich side (0.9V consistently) and the computer seems to be unable to adjust the fuel mixture. Not really sure where to go from here. Any advice is greatly appreciated.

Any results for the exhaust wrap BMC?

BMC

I skipped the exhaust wrap. Didnt realize how expensive that stuff was. I wired in a universal 4 wire and i still have the exact same problem. I have know idea what to do next. I drove the truck to work and back the last two days thinking maybe the computer needed to reset itself to learn the new sensor. I put well over 100 miles on it and nothing. Why do i still have this problem? What do you guys reccomend i do next?

Batman

im having issues related to this also, i have a 4 wire heated from my previous toyota, i just dont know how to go about wiring it into the system. i tried to read the post on how to do so and just got confused. help?

j2the-e

The heater circuit in the heated O2 sensors is duty-cycled by the ecu to precisely control temperature. It is not meant to be on all the time. The only reason newer vehicles use a heated sensor is for emissions. It allows the ecu to enter closed loop operation faster and thus reduce emissions.
Maybe try a better quality single wire sensor. I imagine you cut and extended the wire for the header. Is your wire shielded? How is it routed? Thats important when dealing with such low voltage. Also make sure your connections don't have any resistance.
I had an 87 runner with LCE header and never had an issue.
There may be other issues as well that can cause an O2 sensor code.

trey350

After driving for a while with the new 4 wire Ox sensor hooked up, there was no change in the the gas mileage and I was still tripping an Ox code. I finally dug back in to try and figure out what was going on. Since I knew I was getting a signal from the Ox sensor I decided that the issue must have been in the wire from the Ox to the ECU. I used my multimeter to check for connectivity between the Ox and the ECU and found that there was no connectivity. So I jiggled the wire at the location where LCE reconnected the Ox sensor after adding the header and instantly got a connectivity reading. The wire was shorted where it was zipped tied to the frame. Lesson Learned is don't be to aggressive with zip ties. I replaced the length of wire from the location of the short to the Ox sensor. The check engine light has not come back on. Will update on gas mileage later.

ChefYota4x4

iTrader: (5)

Here was my answer...............

Started with this......




Failed for the first time in 6 visits in 12 years...... Pulled my hair out, and with the FANTASTIC help of Abecedarian, Scope, 4Crawler, ..... had reading, but never enough/it was lazy....... Instead of dealing with welding an 02 bung on the LCE, or adding a heated 02....... And after realizing I had NO REALLY noticeable gains aside from top speed(3mph or so) and LIL more top of the RPM umph(LESS OFF THE LINE).... I did this...................



I also, at the advice of quite a few on here in PM and Jim from 22reperformance.com.... Sold the CAI from LCE as well(which I KNOW was a HOT air intake, as the AFM would get so hot it literally burned me) and slapped the stock Toyota Air Box back on..... Passed smog with flying colors, but had put on a new CAT as well, as mine was literally purple from running lean too much. Starting with a fresh engine and all, I just got tired of screwing with this crap and went back to all stock(Other than quite a bit of engine work/mild upgrades)..... And am VERY happy to have done so. I DO, DEFINITELY notice better mileage and almost identical power(aside from top speed, which has dropped from 93mph to 90mph haha)..... But I gained low end torque, I'm POSITIVE, by getting back the backpressure, etc.

I AM NOT saying my choice was the best one for anyone else... nor that it's a bad header.... In fact, The Putneys recommend that header for their stage 2 motors. And I wasn't sure on the "new CAT" as to whether it possibly was the primary reason(even though the CAT I failed with on the smog was only 18mo old/ran with the LCE header that long as well)... But a friend with a 5 way scope, very limited time, did a quick test of my rig and said, "Nope, it's still passing with flying colors... A/F Ratio is 14.75-1... not bad. LIL higher than I'd want.. but better than the 14.9 it was." SEEMS like, whether or not the LC Header works fine for 99% or not, ... I'm not able to fit into that 1% as easily as I'd like, haha. I'm sure I would have passed with a new CAT, with the LCE.....but the way it was set up, it wouldn't have been long before I'd be going through another CAT... Not TRYING to eat through them, nor do I want to run too lean(Higher Combustion Temps ) ......

And having been through that as well... I'm STILL wanting to slap it back on there with the bung up on the collector or so/Restriction plate like 4Crawler did, installed.... ETC! lol. I DO NOT dislike having that extra room nor MUCH easier collector fix, lol.... I just would have to spend some time to get it right, .....right?

Good info up there, guys... Thanks! After my other projects are done, .........I might just have to do this Heated 02 trick and/or move it up/add a restriction plate, etc. (A guru I know had told me, a couple years ago.... "We used 90's Ford Escort Heated 02's... They work VERY close to exactly like the single wire would on the ECU end.. and are within range for the ECU to easily adjust for the tiny difference. Easily available at any parts store cheap, too." Have you guys, Abecedarian or Scope, heard that?

abecedarian

The cat was purple from running lean? Converters don't heat up much unless the exhaust feeding them is running rich. Ever notice the rotten egg smell when full throttle for a while, like up a grade? That's 'cause the ECU is ignoring the O2 and dumping a bit more fuel than you really need. The egg smell comes from the catalyst getting hot enough to release and recombine sulphur it had been storing for a while.

ChefYota4x4

iTrader: (5)

Never noticed the smell... And I think part of the early CAT failure was due to the 'CATCO' factor as well. BUT, ... I was told by a couple exhaust guys, and I thought Scope, that running lean will dramatically increase internal combustion temps... which can heat up and destroy CAT's as well... Just differently than Rich would. Yeah, I know rich can kill a CAT quick.. and it was always odd to me that I would run such crappy mileage in town(often 12mpg's) and then up to 21mpg's on the hwy. Still working on that gremlin of the 'miss' at idle(nothing DRAMATIC, just annoying) and the idling down to 400rpm at hot restarts, seeming as though it's running on 2-3 cyls while doing so... Then it comes out of it with a lil feathering or just on it's own after a lil longer(30 seconds to a minute) if I don't feather it.

Anywhoooo, after changing back to stock exhaust it still seems a lil crappy on the mileage in town.. 13-17mpg's depending on HORRIFIC L.A. Traffic, lol... but got 23.8mpg's heading out to AZ last trip. That was on refill at Barstow/starting in Torrance Area.

The thing never seemed to smell rich at all when it was heating up the CATCO CAT(while running that LC Header).... But that was a pretty poorly machined first motor, before I did my own with my new machinist. But the tail pipe is always black as coal inside.... Sure does LOOK rich.

I'll get some new pics since the magnaflow CAT and OEM exhaust were put back on.

PS> NEVER, as I said, meant to dog the LC Header.... I just was chasing my tail for so long, Abe, ya know? lol.

abecedarian

You must be keeping your rear window rolled up.

And that's not the stock exhaust manifold for an '87 RE.
22R, maybe.