AJCady

I have a 1995 SC 300 from Texas.

Unfortunately the check engine light is on because the previous owner replaced the ECU with a unit from a California spec sc300. ( The ECU is looking for a sub O2 sensor that's installed on California cars but not present in the federal versions. )

I considered replacing the ECU but they're pretty expensive so now I'm thinking about just installing a sub O2 sensor on my car so I can clear the blasted code and have a functioning check engine light again.

I'm comfortable working on engines so I'm inclined to just remove my existing manifold and weld an appropriate fitting to add the O2 sensor.

Does anyone have a photo showing the location of the sub O2 sensor on a California spec car? I have the manual but the images aren't very detailed.

Thanks!

KahnBB6

iTrader: (5)

I moved this to our Performance and Maintenance section

Do you have an original 5-speed model? If not, I would highly recommend sourcing the correct Federal 49-State ECU and just put that in. They are not that pricey or difficult to come by (used). If you have a 5-speed car I'd still recommend this but it would make far more sense why you'd want to wire in the 3rd O2 sensor.

A couple of reasons why I recommend just sourcing a Federal ECU:

One... Cali smogs cars based on their VIN code and you will actually have an easier time passing tailpipe/dyno tests by allowing the car's emissions system to operate as it was designed. Cali and Federal cats are of slightly different spec for those years as well.

No, the smog technician will not be able to tell if you have a Federal or Cali ECU in the car but the Cali ECU may be doing other subtle things that might produce different tailpipe numbers than a Federal one.

Two... the #3 O2 location is actually in a PITA to replicate location at a 45-degree angle ON the #2 catalytic convertor. The two easiest ways to get one on there are to go to a muffler shop and get a custom legal weld-in universal cat that matches the SC300 (although I've heard you aren't even allowed to up-spec a car's emission system here... unless you have the BAR inspect it and give you a sticker)... or you can just find a #2 cat from a Cali model.

A replacement factory Cali cat that is "direct fit" is also kind of sort of available... but it still needs the #3 O2 sensor bung welded in. This, despite the cat having a legal CARB E.O. number. The only such model available is a Catco #66266. Universal weld-in might be the better bet.

Alternatively, if you went with replacing your ECU with another Federal OBD1 Automatic computer (unless you DO have a 5-speed), then you could buy one of those Catco #66266's whenever a replacement is needed and just forget about it. There is no requirement in Cali that you make a Federal car into a Cali car. You just can't downgrade a Cali emissions system to Federal.

Here's page 2 of a thread on the topic of the cats in question:

https://www.clublexus.com/forums/sc-...a-legal-2.html

And here are some reference pictures from vigman's USDM GTE swap thread. Please note that what I am showing him is a 50-State USDM 2JZGTE #2 cat and not an MKIV NA or SC300 #2 cat... but other than a 4" difference in the pipe length closer to mufflers this is exactly the same as what a Cali-spec 92-95 SC300 #2 cat looks like, including the bung.

https://www.clublexus.com/forums/bui...ar-2-a-10.html

t2d2

iTrader: (8)

I imagine you would come out ahead financially by buying a regular ECU (used) and selling your Cali one, as opposed to upgrading other stuff to match the Cali ECU.

KahnBB6

iTrader: (5)

^^ Yes, very much so. Since he didn't say whether or not he had an automatic or 5-speed car I wanted to give him info he might need if he indeed has the rarer model with a harder to source M/T ECU. Still, even then I do see them around on ebay and up for sale here and on SF.

AJCady, I think I have the Federal and Cali M/T ECU part numbers in my notes if you need them to confirm. Again... assuming that's the issue.

AJCady

Thanks for all the advice and information

Just to clarify, The car does have an automatic transmission. I live in Boston Massachusetts so the omissions bags are quite as strict as California but your points regarding subtle differences in behavior of the ECU make a lot of sense

Any suggestions on where to look for a reasonably priced ECU? And how much should I expect to pay?

t2d2

iTrader: (8)

You can find them on eBay, or check with aliga here if he's parting out a car. You should be able to get a good one for under $150, or ~$250 if buying a refurbished one which hopefully means the capacitors have been properly serviced.

KahnBB6

iTrader: (5)

^^ Seconded.