This here is a cautionary tale for you lads. Last year, just before smog inspection time I got a check engine light for catalyst efficiency on my 2002 sr5 (A.K.A BRUTUS, because I'm sure hell stab me in the back one day when Im not looking).

Managed to bluff my way through inspection, buying myself a few months time but I knew I had to get this thing fixed. Did some forum searching on here and determined that it's far more likely that its the 02 and A/F ratio sensor, my rig being California CARB compliant so decided to order myself replacements.

looked up the correct part numbers off of Denso's website and incorrectly assumed that all parts with the Denso stamp on them are created equal. The correct part number for my upstream was 234-9002 and shopping around I found one for half the price listed on E-bay. Ordered both the sensors but didn't get around to installing them until 2 months back because the rig was running fine.

Once I replaced the sensors (threw away my old A/F sensor, yes I am a highly educated idiot sometimes) I cleared the codes with my OBD2 scanner and started driving. Immediately noticed jerky acceleration as soon as I replaced the A/F ratio sensor. The Cat efficiency code didn't come back but last week, a week before I'm due to register the car again hence smog inspection time, I got a P1135 which is an A/F Ratio sensor code plus the jerky acceleration/idle which I was hoping was an ECU calibration issue never went away so now I'm stuck with limited time in which to figure out where to order a new 234-9002 from and then run the drive cycles to pass SMOG in order to register the car so YEAH.

TlR bought a cheaper Denso part from E-Bay and got screwed.

Well you could have gotten screwed Or there really is something to the P1135.

Our beloved FSM says it's one or more of these causes:
Open or short in heater circuit of A/F sensor
A/F sensor heater
ECM

So are you Sure it's not a shorted wire, connector or ECM?

Luck and enjoy the runner.

A/F sensor heater is whats showing up on the OBD scanner. Since it started as soon as I put in the new A/F ratio sensor, I'm about 60% positive that its the sensor.

So grab a DVM and check the heater resistance on the sensor.

If it's in spec, problem is in your wiring.

I get my Denso sensors on Amazon, never had an issue and good prices.

Attached Images

SF-54 Inspection (2000 4Runner) Heated Oxygen Sensor (Bank 1 Sensor 2).pdf (45.3 KB, 133 views)

I've bought Denso oxygen sensors from this place several times in the past. They even worked with me when the 'officially recommended' part number had too short of a wire on it.
403 Forbidden Densoproducts.com, a badge of sparkplugs.com.

Thank you so much for the advice & suggestions.

I'm looking at Rock auto for 234-9002 @ $125 I've heard that they are a pretty decent source for parts so thinking of going with them. I really wanted to find a 2002 Sr5 in a junk yard around me that I sould just pull the sensor from but the only one within 50 miles had the whole exhaust system cut out plus I have realized that the worse rust and rounded bolts to be found anywhere on these rigs is usually on the exhaust, my own took about a half a can of butane to take off so I shudder to think of that nightmare scenario.

That sucks. I've had a similar issue with MAF sensors, they are selling on Ebay for like $15, complete with the Denso logo and correct part numbers. I've tried one, and my LTFT numbers went through the roof. I'm convinced they're Chinese fakes.

The problem is how to know you're getting a genuine OEM Toyota or Denso part, unless buying from a dealer?

I don't even trust Amazon let alone ebay for parts. NAPA has denso parts.

When I replaced my o2 sensors last year I too bought a pair of universal fit Densos off ebay that ended up throwing an error code. I was able to return them minus a rediculous 20% restocking fee. Then I bought a new pair from Amazon that were specific to my model, and they have been 100% trouble-free ever since.

mind throwing a link from your purchase history for the A/F sensor? I want to buy from the specific seller you bought from so I don't get "Fool me once shame on . . . you . . . . thing is, I cant be fooled again".

https://www.amazon.com/Denso-234-416...Toyota+4Runner

https://www.amazon.com/Denso-234-415...0KKH0HTYCN93QN

Update: Ordered myself a new A/F ratio sensor off of Amazon and it fixed the problem immediately. No more jerky acceleration and the CEL hasn't come back yet. Now I just need to complete all those damned drive patterns and get the monitors ready for Smog check in the next 4 days.

Ebay is shady AF.

When I replaced my sensors, they had 102k miles on them. They didn't throw a code yet, but I was getting some pinging and exhaust fumes through the back window. The new sensors fixed those problems and more.

even amazon has fake denso, you really have to look and read reviews.

sometimes you have to think too....let me see denso knock sensor...at dealer 120, at napa 90 amazon "denso" 45 ( with reveiws saying not legit) and then ebay denso , 2 for 25 surely the ebay ones must be legit