SactoSC3

I'm selling my '92 SC300, so I took it to get smogged today in NorCA. The smog tech told me he's supposed to find 3 O2 sensors, but could only find 2. The two were on the passenger side of the engine block and pretty prominent. Where is the 3rd O2 sensor? I put the car on a ramp and looked all around the converters and could not locate any. I am reportedly the 2nd owner on this car and it is virtually bone stock. I doubt that anyone would have put on a stock cat-back exhaust and bypassed the rear-most O2 sensor. Anyway, if the group could help me find the 3rd, I'd really appreciate it.

Oh, and if anyone is interested in the car, hit me up. It is in Sacramento, CA. 87k miles, auto, pearl white/tan int.

Supra Dr

iTrader: (14)

There should be 2 up top before the 'Y' merges into the 1st catalytic converter. The 3rd is in the
pipe before the 2nd (Rear) catalytic converter just after the flange where the two converters bolt
together. Look bout 6" behind the flange & the O2 should be there.

SactoSC3

1997Soarer

iTrader: (1)

For future reference, Cali-spec 92-95 SC300s have 3 O2 sensors just like 96+ OBD2 SC300s. Two O2s pre-cat, and one post-cat in the trans tunnel, almost under the passenger seat footwell.

If your car is relatively stock, and you didn't see a rear 02, that means your SC300 was a 49 state compliant car. Illegal for road use in California.

KahnBB6

iTrader: (5)

Just so the OP knows, those first two O2 sensors come before the first catalytic convertor and for CA Emission 92-95 and ALL 96+ OBD2 SC300's that third O2 is actually bolted into the corner of the 2nd OEM cat with a little upward turned heat shield slightly obscuring it other than the long wire that leads up to a transmission tunnel grommet.

CA legal aftermarket cats for CA Emission SC300's don't often even have the correct O2 sensor mounting area. The thing to do with those for anyone curious is to take the worn out SC300 #2 catalytic convertor and have an exhaust shop cut out the OEM 3rd O2 sensor mounting flange and weld it on the pipe in nearly the same location as it would be if the aftermarket cat had the same mounting area built into its housing (which it will not since its aftermarket). Welding that stock flange as close as possible post #2 aftermarket cat is what will make that 3rd O2 sensor... and the smog techs... happy again.

Sorry but that last part of this is incorrect. 49-State emission compliant cars are legal to register for road use and smog in the state of California. I have done this before moving to CA with a 49-state emission car that was stock. If you haven't owned it for a year or more you will get hit with higher DMV fees when you first bring it in (not so much if you have owned it for a year or more) but other than that you take it to get smogged like any other car in California. Further, you only service the car with the 49-state emissions equipment it was originally manufactured with. You are not required to change a legally CA registered 49-state emission vehicle to match the spec of its 50-state or CA Emission spec counterpart.

It's just the other way around that is illegal in CA: you cannot modify a 50-State or CA Emission spec version of a car into a 49-state Federal or any other emission spec unless whatever you're changing it to is another higher level of cleaner/less polluting spec (if applicable)... or if you've converted to full motor and battery electric drive.

The VIN number, under hood emission sticker and ECU part number label will all indicate if it is a Federal Emission 49-state car or a CA Emission SC but generally unless someone tried to delete the 3rd O2 sensor, if there isn't one there on the second cat just underneath a tiny upward facing head shield then it never came with one.

The 3rd O2 sensor in the 1992-1997 CA Emission SC's are really just 4-wire heated O2 "check" sensors. They actually have no effect on how the ECU adjusts engine and emission performance. It just reacts and triggers a CEL code if the 2nd catalytic convertor is not detected to be within a certain operating temperature range. The ECU's engine control and adjustment is only influenced directly by the first two O2 sensors located on the headers just before the first catalytic convertor.

1997Soarer

iTrader: (1)

^ Good to know about that last part. I thought it was illegal for you guys to keep out of state cars that hadn't been converted.

KahnBB6

iTrader: (5)

No problem! No, not illegal at all. Just illegal for original sale brand new in California. But you can bring your 49-State Federal car into CA. It has to get smogged every two years like all other cars but the testing computer, per the VIN number, goes by the 49-state standards it was manufactured to meet.

You just can't change a 50-state SC300 into a 49-state SC300 and be legal there. By the CA-spec SC300's VIN they expect that chassis to meet the 50-State CA Emission spec as originally designed. Or better, if such a drivetrain upgrade that gets BAR approved exists.

For instance, my CA spec 93 SC300 has to stay at least as compliant as the CA spec. So since my 1993-95 spec swap is of a 50-state emission standard that is legal. The FULL driveline and controls are at least the same model year or newer than the original engine system. If the same all stock USDM swap were done to a 49-state Federal SC that would technically be considered an emissions upgrade for that car.

It would be too much of a hardship to have a mandatory rule that demands people convert more plentiful 49-state emission cars to 50-state emission specs before entering CA. A) less availability of parts B) sometimes way too complicated to even consider C) The Federal cars were manufactured one way and certified to operate that way so changing all of them that enter CA would be beyond the means and capabilities of most people.

The only case where it is kind of required up front is if you import a gray market vehicle (such as a RHD JDM car). In that case unless you swap in a USDM emission legal stock engine setup (and every single emission control system for it) that is the same US model year spec or newer then you have to get the original engine specially modified to pass the U.S. market CA emission standards for the original model year of that gray import chassis. Then you have to get it lab tested. It can cost $10k-$15k to do. An example would be making a 1990 Skyline GT-R's RB26DETT emissions compliant to CA standards for the 1990 model year. That has been done many times already and continues to be. It just isn't cheap!

But to return to the main thread topic... this is also why a 49-state Federal 1992-1995 SC300 does not need to have the CA-Spec 3rd O2 sensor and wiring added, plus the specific year and trans CA ECU and other changes.

They'll let you bring a Federal SC300/400 in from out of state no problem. If you JUST bought it the DMV and tax fees are higher one time but that's the case in most states with a car someone has owned for less than a year. The car just has to be maintained to meet the emission standards it was originally designed for and modifications to the driveline all have use CARB approved E.O. numbered parts for that make, model, model year and trim level just the same as the CA Emission counterparts.

If you bought a car that only ever had 50-state (CA spec) emissions controls no matter where in the U.S. it was sold then none of this matters as all the cars of that model and trim were the same anyway. Again, if you only have legally owned it in your name for less than a year the taxes and DMV fees to bring it in are higher. That's the case in almost all 50 states.