By the way, Bo, my last was quite long. just to re-inforce the point on Oxygen sensor...
You need the original equipment Toyota one,OR the correct part# made by the Original equip. Manufacturer. It's interesting that the Toyota part#'s only differ by ONE digit. That means something. Could be build date-before/after a certain calendar date of manufacture, different emissions system, even an Export car model to different country or market. I'd go ask that parts guy again and find out what the different #'s mean. Sometimes on certain parts like the O2 sensor, you have to dig harder for the answer. Ask Karl!!
It is possible, just possible, that the Denso one could be correct, as Denso is a Japanese part maker/brand. Toyota most likely sourced the O2 sensor from a Japanese maker. The correct part will match exactly on the wire plug and prob. wire colors. To add further confusion, it is possible that the original Toyota part# Or the Denso # has been replaced by a new part#. This happens w/some parts. So, I would ask the Toyota, or a good parts store person, to help figure out this issue. A good parts dept. or counter-person will be able to help you on this, you might need to speak w/ more than one. Act confident, be friendly but persistent. IF you act like you understand the "parts game" they usually will go out of their way to help. I have found it useful to have different parts stores and sources to work with. In USA besides a dealer, NAPA is a good chain of quality reputable Parts stores, I don't know what you have access to in Thailand.
Another option,for knowledge/research, is find a good shop that works on/has experience w/ Toyota's. Your car is simple compared to today's cars. On most parts, we have options as to which ones to use, but we learned on O2's the Original is by far the Best. Keep at it Bo, we appreciate your efforts, we all learn together!
Gadgetman Reno, NV
Bo, I'd use an aftermarket O2, if a new factory part is too hard to find. Your car looks like there's only the one O2 sensor, OK. I don't have/go by direct experience on this,(factory vs. Aftermarket) but by experienced experts' advice. But a correct part will at least have the exact wire plug and mounting design, and will match these things exactly. I'd at least stay w/ a Japanese-made brand, like Denso, or maybe NGK.
Those scans of that manual, is that for your year engine? Get a pic of the book's cover it's a clue. These are diagrams of the overall computer system and the components involved, it's relevant IF it's the one for your exact car. But the vacuum circuit diagram is a different one. This seems like a typical system from about 5-10 years earlier than 1994, at least what we see here in USA. I see a cold start injector in those diagrams, I always thought those were in early models of injected systems,1980's not 1994. I'm not expert, but I wonder when I see this. Maybe they still used cold start inj. for your particular car? The Cold start injector was used in early systems with less sophisticated methods, they just put in extra gas for cold starting, instead of having ability to add more gas thru the regular injectors. This extra injector is like the choke on a carburetor, only works when engine is cold.
Again, I wonder if Toyota had different versions, using an older/different design for an Export model to Thailand? Emissions regulations may be different for Thailand than USA or other countries. All this matters in finding correct info for YOUR car. Emissions regulations by country/region often dictate different designs. Again, I only ask cause of that cold start injector in the diagrams. another idea- If your engine has that cold start inj., then it's also possible the computer will be more co-operative w/ our mods, as to me that injector is evidence of "looser" or earlier yr. computer control specifications, like the "old days" here in USA.
Bo get a pic of the vacuum circuits diagram for your exact car, if possible. Check to make sure it's the correct one, we see these diagram stickers underhood on most cars here in USA. It WILL exist either under the hood, or in a book. When looking in a book, you have to reference by engine series,transmission, year, and country- Japan, USA, Thailand, or maybe just Export.
Don't be discouraged if some shops /mechanics aren't helpful. But I know people do mod's to cars in Asia, you already have the Propane mod. In Indonesia, Malaysia, Bali, Singapore, etc., folks use mod's like HCS and other stuff already. What about the propane mod you have-did car already have that, did you do it yourself, or have it done? I'm just thinking out loud trying to imagine who you could talk to over there someone familiar w/ your car/engine.
Gadgetman Reno, NV
The following user(s) said Thank You: Timothy Eason