Upstream or downstream?

is it possible to tell where this sensor should be located. it came out of a 1999 SR5 4WD AUTO 3.4L 4RUNNER.

does anyone have the page from the digital FSM where I could find the factory circuit diagram with the factory part numbers. please.

does anyone have a photo of a bank1 sensor1 A/F sensor, and or the legit part number.

my suspicion is that this is NOT AN A/F SENSOR, which explains why the scan gauge can't report A/F ratios

thanks everyone

 

You can go to PARTSOUQ.COM
Enter your VIN (since you have a 1999 SR5 4Runner)
Search the parts diagrams. If both sensors are the same part number, then you have your answer.

 

brilliant ! on what page, in the unsearchable digital FSM, could I find those part numbers. TYVM ! I appreciate your consistent help.

 

On partsouq.com, I found, for my car, both sensors on the diagram "Switch & Relay & Computer" in the Electrical section. It was the diagram with the engine.

For my year there are a few options. If you really want to know what is supposed to go on your car, call the dealer with your VIN. They can run it and tell you the exact emissions part numbers for your car.

A good parts guy who is being friendly with some time, will help you look up alternate cars it fits or would come on.

Also, you can take the part number you get from the dealer and plug it into online TOYOTA dealer parts sellers and they often list all the cars it fits. Good for when you go to a junkyard and see 20 early 2000s TOYOTAS and Lexus cars but no 4Runners. Sometimes your part may be on a different model.

However, for emissions...I'd just buy new whatever the dealer told me was the correct part. Used emissions parts are usually near the their end of life.

 

OK thanks, that helps. So I've discovered that an A/F Ratio sensor does NOT belong in a 99 truck unless and only if is is a cali model, in which case it should have 2 cats. Although the Denso site said at one point that my runner could use a -9003 A/F Sensor, in another spot it told me that only cali trucks have an A/F in Bank 1 Sensor 1 spot. which makes Denso's next best guess is 234-4162 in both holes. One big clue is that the 1 and 2 spot have different connectors ON cali runners, and identical connectors on the single cat rig I have. I suppose to keep me from putting an A/F in hole 1. However I have still not discovered the page in the FSM that IDs those pigtails and connectors. I did find the electrical and can see the path through the ECU.

thanks for the info and response. this seems like a very sleepy forum for shade tree mechanics.

 

Yeah, do NOT go by any other source but TOYOTA. Denso won't have the nitty gritty details. Only your dealer will. And yes on the connector being different. Had another person who couldn't figure out why his new O2 sensor wouldn't plug into the wiring harness. I recommended he contact the dealer and sure enough it was an AF sensor he needed and he was all good.

 

there a portion in a toyota drawing, i think, showing the method of replacing the connector from a sensor to mate with the one on the harness. It makes me think about making a crossover connector that will allow an AF to plug into the O2 harness, but that wouldn't do any good if the ecu can't use the fuel trims. my main question when i get to the mechanic is whether the ecu can process AF data. because now I know how to do it.

 

There's a reason why the plug is different. The ECU is just going to be confused.