Sorry..OT Toyota O2 sensor question

[Wil Ferch]

I have 94 Geo Prizm ( Corolla) with 1.6L 4A-FE engine, 3 spd auto, but with Calif emissions control. The second ( "sub-02 sensor") oxygen sensor disappeared...blew off. Oddly this second O2 sensor is also ( like the main sensor) in-front of the main converter...not behind it like OBD 11 cars of 1996+. I think this downstream unit is "downstream" of a light-off converter that may exist at the exhaust manifold...dunno.

Does this second-downstream sensor provide a feedback control function?...or is it only a monitoring function? Will it hurt the engine to run without it? I'm debating whether to spring for a new $ part..or simply fab a gasketed cover plate for this flanged unit.

Porsche content...answer may be transferrable to later Porsche models.

---Wil

[911SCfanatic]

Wil, can you wait a couple of days for the answer? I have an OBDII control systems book at home I can check. If you can wait, PM me and I will reply in a couple of days.

[Wil Ferch]

Bill:
Nice attempt, I truly appreciate any help on this one...but notice that I'm speaking about a 94 car...it's OBD 1.

Lot's of difficulty with local parts stores about *two* sensors in front of the main cat ( OBD 11 has one in front...one behind).

I think the sequence I have is:

- exhaust manifold...main sensor....warm-up cat.....second sensor....main cat ......muffler ..... exit ....

---Wil

[KobaltBlau]

Normally any O2 sensor failure will not hurt the engine. The ECU will "realize" it's getting a bogus or no signal, and go to a default mode, usually richer. May not pass emissions. Other than that I don't know.

edit: I know nothing about how this specific ECU will perform. I'm just stating my experience with modern EFI in general.

[911SCfanatic]

That's a 4 banger, right? Otherwise I was going to said that it was one O2 sensor for each bank of cylinders, which is what they do for some OBDII vehicles.

On the OBDII thing, there are pre-96 cars that have it. My 95 Sonoma is OBDII. Coincidentally, I worked at GenerousMotors at the time on the very same powertrain. The deal is that some auto manufacturers did a partial roll-out on some models prior to the required date of 96. As a result, auto parts stores are puzzled when confronted with my car and parts don't show up properly. I have had to go to the dealer parts department a few times to get straight answers. I have even heard that some cars as early as 94 1/2 may have OBDII, although I have never been able to confirm this. Maybe you have one of these bastards? One way to confirm is the diagnositics plug.

[Wil Ferch]

No...it's the V-12 Geo Prizm....



Of course it's a 4 banger ...

The real PITA is that sensors all operate pretty much in the same way. The "proper" Bosch part that the cars-part salesman sold me was $50. Didn't fit. The flange size was all wrong. So....to get the right flange size...the dealer ( either Toyota or Chevy...as well as another independent parts place)...will (now) gladly sell me the right part for about $170. Holy smokes ! Because the flange is different? It's a simple 2 wire sensor.

Since I fabbed a cover plate ( simply to mask the heat/noise from the "hole")...I'm tempted to buy a generic sensor and place it in a drilled/tapped hole in the fabbed cover plate I have. Splice-in the wires and we're ( prolly) set.

How 'bout that ?? If i do this, do I need to "zero" any fault codes? Car runs fine and has no dash lights that came on.

--Wil

[KobaltBlau]

If you know it's a narrowband sensor you should be able to replace it with another; I think they are almost all the same voltage range (correct me if I'm wrong!!). I have no clue how to clear fault codes on a corolla, but if the check engine light didn't come on I wouldn't worry, especially on OBD1.

[911SCfanatic]

I thought I was being generous with the 4 banger thing--I was thinking it might be a 3 banger!

Try this place. I've had luck with them before.
http://www.oxygensensorwholesale.com/geo_1994_prizm_lsi.html

Looks like its only $55.93--if it's the right flange. Maybe they can give you the measurements. Compare the part number with the wrong one you've already tried. You can clear the fault codes by disconnecting the battery or using a scan tool to delete the old codes. Autozone does it for free.

[BURN-BROS]

94 and 95 cars had a transitional system to obd2 FWIW.

[Porsche_monkey]

Originally posted by KobaltBlau
If you know it's a narrowband sensor you should be able to replace it with another; I think they are almost all the same voltage range (correct me if I'm wrong!!). I have no clue how to clear fault codes on a corolla, but if the check engine light didn't come on I wouldn't worry, especially on OBD1.

I think as along as the number of wires (heated/unheated) you are correct. Having said that my Volvo ran totally rich on a cheapy aftermarket O2 sensor, then ran A1 on the Bosch $$$ dealer part.

I would just double check the wiring again before I used a cheapy.

[RickM]

You may want to call Bosch directly and ask to speak to a tech rep. They are usually very helpful.

Bosch Customer Service:
888-715-3616
(Monday thru Friday 8:00 am to 5:00 pm CST;
for U.S.)

[Wil Ferch]

RickM--- I've got a call out to Bosch...thanks for the link
Bill G---that's the part I got locally ( 12201), also tried 12031. Both flanges were *way* too small. Computer says its correct.

Thanks all...will report back findings...

--Wil

[911SCfanatic]

Wil, I feel your pain, which is why I want to help so bad. I went through this same BS before. It feels like you're in O2 sensor hell.

[Wil Ferch]

It's only hellish when you're under the car....putting in a part that required 3 trips to the dealer/ parts place...and then it doesn't fit.

It'll come right.... even if it ends up being a home made brew of generic sensor...a Jerry Woods O2 sensor bung ( $10)....some welding on a plate, etc. If Thom Fitzpatrick can do it...why not any one of us ???

--Wil

[Wil Ferch]

Ok , we can close this thread....

It seems there are 44mm and 54 mm flange type sensors. Bosch info form their US HQ is all wrong on this, as they aren't the OEM supplier. Found a reasonably priced ( $48) sensor of the right type from Denso.

Thanks to all on this board who helped. FWIW...I got "banned" from the BAT database because I had the temerity of asking for info verification. Obviously, I was expected to unquestionably agree with any self-appointed experts. Oh well.

--Wil

[RickM]

Wil, How'd you find out Denso was the supplier? Any online DB to reference in the future?

Good to see a problem solved.

[Wil Ferch]

Rick:
It was largely by acident. My continuing talks with the ( otherwise knowledgable) Bosch Tech rep led to nowhere. I then casually asked if Bosch was the OEM suppler for this application. Answer is "no"". Hmmm...maybe that's why the Bosch info is no good. Did a thorough Google search on oxygen sensors and found a few places that identify their parts by brand name ( Walker, Denso, Bosch) and focused on the other brand names. I focused on the Chevy and Toyota parts numbers, and used these as cross-referenced lists to any "non-Bosch" units available.
Viola...sparkplugs.com .. as well as a few others, list parts this way and I was able to determine that flanged units indeed come in two sizes..44 and 54 bolt spacing patterns. The numbers and sizes and factory numbers all cross-matched.

Jeez..I feel like one those TV detectives to get anywhere !

-Wil

[Wil Ferch]

Hmm..my reply didn't post properly although it says it did. Let's try again.

It was largely by accident after the Bosch rep admitted that Bosch is not the OEM suppler. I went to various places after a Google search to find any web sites that identified brand name ( Denso, Walker) that weren't Bosch, in addition to providing cross reference numbers to the spendy dealers OEM parts numbers ( both GM and Toyota).Found..among others.. sparkplugs.com ...and they listed in this fashion in additon to the text identifying these as either 44 or 54 mm flanges. Aha !

You gotta be a detective or an archeologist to get anywhere with parts nowadays.

--Wil

[ryan j]

The California spec 1.6 uses two sensors, but they both aren't technically called O2 sensors. The first sensor is an air/fuel ratio sensor and the second is the O2 sensor. I'm told it's an emissions deal for the California cars, as the Federal/Canada cars only use one. The air/fuel sensor is essentially and O2 sensor, but Toyota tries to put some kind of mystique around it. It acts exactly like an O2 sensor on the scan tools. As for using cheap sensors and splicing wires, I wouldn't recomend it. the range that these things operate is small and any change in resistance will have adverse effects on its performance.

- The two problems with those cars are O2 sensor failure and starters. If you don't have a manual tranny, change your starter at about 120k (if it makes it that long), or carry a spare and the tools to change it. it's under the intake manifold in the back, kind of a pain to do without a lift.

[Wil Ferch]

Ryan:
Thanks.
As you can see...I found a reasonably priced proper replacement part. The scrooge in me just couldn't stomach a 300-400 % premium because of a goofy, specific mount.
Ahhh...these cars last a long time. It's the third Corolla/Prizm that are ( all at the same time) in my extended family. We don't need honkin SUV's and the way the family operates...we travel almost individually and for long distances. Spec requirements: cheap to buy and run...and must be reliable. One of these has passed 226,000 and still going strong. I've replaced he starter..yeah..a *bit* of a pain...but not any more so that gaining access to a Carrera voltage regulator inside the fan / alternator. These cars have met the bullet proof daily driver spec I need so I can concentrate properly on my "hobby" car...the 85 Carrera Silver Bullet.

Th odd thing about this 94 Prizm of this thread...it was originally delivered in upstate New York...and never needed Ca emissions package, but was delivered this way. Our other 94 Prizm has the Fed package...one sensor.

Wil