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Having trouble getting my car to pass smog. I have a 92 sc300 and I live in California. Can someone please confirm if the O2 sensor was put in the correct location?
The reason I am wondering is because when I ordered a replacement catalytic converter about a year and a half ago i specified that I lived in Cali but the cat didn't come with a place for the O2 sensor. ??? My friend said he would just weld it in place. At the time I just over all the repairs and stupid people making stupid mistakes, so I told him just to go ahead and do it.
Now I'm concerned maybe it should have been placed behind the rear cat instead of in front of it. <br >
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Is your SC300 a Federal or California car? There are two O2 sensors at the ends of the two cast-iron exhaust manifolds on all the cars. California cars have 4-wire sensors, federal has single-wire. The photo below shows Federal O2 sensors.
The California cars have an extra 4-wire O2 sensor after the catalytic converter but I don't remember exactly where (I have a federal car so I don't have to worry about it even though I live in California). What are the results of the smog check? The problem may not have anything to do with the O2 sensors; too little information is known at this time.
I don't know about the sc300, but if it was an LS400 there are 4, O2 sensors. 2 upstream and 2 down stream.
The upstream are the ones shown in the picture above of the manifolds, and down stream are on the outlet of the Cats.
Oh and in CA you can't just use any old cat, it has to be a factory part, I don't think they approve of anything else. I would love to put a political dig here now.
I don't know about the sc300, but if it was an LS400 there are 4, O2 sensors. 2 upstream and 2 down stream.
The upstream are the ones shown in the picture above of the manifolds, and down stream are on the outlet of the Cats.
Oh and in CA you can't just use any old cat, it has to be a factory part, I don't think they approve of anything else. I would love to put a political dig here now.
Not on his 92, it's OBD1 and only has the 2 shown.
I have had the same thing done very recently. Yes, that is the correct location... or as correct as you will be able to get it with an aftermarket cat. Did you order a Catco #66266 "Direct Fit" model? That is correct for your Cali model to pass smog but Catco/Airtek/AP Exhaust annoyingly did not put the #3 O2 sensor flange in the correct location when they built the piping.
So you have to cut out your original #3 O2 sensor flange on your original cat and have it welded onto your replacement aftermarket cat pipe.
On OEM SC300 (and Supra MKIV) secondary cats for Cali models the O2 flange is ON one corner of the cat itself. So you really can't do more than get it as close as you did in your pictures. I did this also with the same Catco #66266 Direct Fit model on my car right now. But after that you'd be wise to just continue to use the aftermarket piping with the O2 flange in place and just replace just the catalytic convertor every couple of years when it goes out.
The Catco #66266 secondary cat is nearly discontinued (but it is totally still legal) and its replacement is a made-to-order #93266 Direct Fit for Cali SC300 models (meaning you call Airtek/Catco directly and ask them to make one for you). I have been in touch with Catco and I am sending them notes and pictures to at least get the O2 sensor flange location corrected. Maybe the poor pipe fitment too which requires some cutting and re-welding to get everything to bolt in place like an OEM cat/pipe. It's close but needs some work to fit. Note that you can still use a universal type cat if you want to have piping made.
The actual function of that sensor flange where you have it welded is just fine . My car has it set up the same way and the #3 O2 sensor throws no codes. You'll be fine. Just use the factory-type Denso #234-4214 sensor for that area.
You don't want to put the O2 sensor after the cat. That's not the way Toyota designed it. Very close to the cat will do about the same as the original cat's design.
And this is not a sensor that actually controls the engine tuning. It's just a "checking" sensor. It has to be there and read certain signal ranges based on the exhaust but that's all it does.
The two front O2 sensors are the active sensors just as with Federal models. Things only got more complicated for 1995+ Cali front sensors and 1996+ Federal sensors on SC300's.
Here are some rough pictures I took of my aftermarket secondary cat setup the other day. Catco #66266 Direct Fit. Cut and re-welded the bends a bit in 2014 to fit like stock. The O2 sensor location was redone in 2014. Ladt week I just had the cat itself replaced with the same model.
O2 sensor flange location very similar to yours as you can see. I've had no issues being placed this close, however it does need to be as close to the secondary cat as is possible given the constraints of that last pipe bend. You CANNOT weld the flange onto any new aftermarket cat as this would be considered compromising the cat. It just has to be close like this. No one makes an aftermarket secondary cat with the flange ON the cat the way Toyota did.
And a couple of comparisons of an UN-modified Catco #66266 with an MKIV Supra TT secondary cat which is nearly identical to the SC300 OEM California secondary cat in terms of O2 sensor placement and pipe bending. Do note that the unmodified Catco cat pictured here would need some modification to actually bolt in correctly. See the layover comparison.
Federal SC300 OEM cats lack the #3 O2 sensor until.... 1996... I *think*.
the rear o2 sensor is only responsible for setting off the catalyst efficiency code.
if there is no code and your numbers are failing... its not the rear o2 sensor.
looks like they put it in the right spot though as already confirmed.
05-23-16, 04:27 PM
EASY O2 sensor question. PLEASE HELP.
. My car has it set up the same way and the #3 O2 sensor throws no codes. You'll be fine. Just use the factory-type Denso #234-4214 sensor for that area.
