02 Sensor Help!

[TegoXR]

About to purchase an 02 sensor for my 3rd gen but was wondering if it really matters if its before or after the cat. Already replaced the 02 sensor after the cat and that didn't solve anything and still have a check engine light. I've been lurking and searching like crazy and some sites doesn't state after the cat or before the cat...does it really matter, an 02 sensor is an 02 sensor no? Any help would be greatly appreciated!

Thanks,
Fred

 

[kball]

Your precat sensor is an air/fuel sensor. It's different than an O2 sensor. Check here: http://www.densoaftermarket.com/catalog/catalog.php?part=afrs

 

[TegoXR]

So this ones ok?

OEM GENUINE TOYOTA Tacoma 4Runner T100 Air Fuel Ratio Oxygen Sensor 89465-39835 | eBay

 

[TegoXR]

Now would I be looking at an upstream sensor not downstream?

 

[kball]

Sorry my mistake, 99's can be either Calif emission trucks or Fed so you need to know which one yours is. I can't tell you about that ebay sensor since it lists a Toyota part number not Denso.

 

[kball]

Now would I be looking at an upstream sensor not downstream?

Yes, upstream is pre cat. Downstream is post cat.

 

[TegoXR]

Thanks buddy!

Now how would I know if mine is a calif emission truck?

 

[kball]

It should say under your hood. I think for the 99-00's it's as simple as, do you have 1 cat or 2? If you have 2 then you have the Calif emissions. If you have 1 then it's Federal. Maybe someone with a 99-00 will chime in. I have a 96 so I don't have to worry about such nonsense LOL.

 

[SliderNH]

the easiest way to determine if it is a CA emissions truck is to call the dealer with the VIN, they can tell you. For parts, especially sensors, get toyota OEM parts. Go here: TRDparts4u accessories for your Toyota car, truck, 4x4 or SUV with Genuine Toyota and offroad specialty parts.

Find what you need and you can call your local toyota place with the webpage information and they will do a price match.

 

[TheDurk]

the easiest way to determine if it is a CA emissions truck is to call the dealer with the VIN, they can tell you. For parts, especially sensors, get toyota OEM parts. Go here: TRDparts4u accessories for your Toyota car, truck, 4x4 or SUV with Genuine Toyota and offroad specialty parts.

Find what you need and you can call your local toyota place with the webpage information and they will do a price match.

There is ZERO chance my local dealer would pricematch the price I get my OEM Denso sensors on Amazon. The dealer charges twice as much for the exact same part (minus a red box). Just get the Denso part number from http://www.densoaftermarket.com/catalog/. Then Google the Denso number and paste it in the Amazon search bar and take the best deal you find (usually it's Amazon...). I still maintain counting cats is easier and more reliable than trusting a dealer not to eff something up. I remember a case on here where the dealer got it wrong.

 

[TheDurk]

About to purchase an 02 sensor for my 3rd gen but was wondering if it really matters if its before or after the cat. Already replaced the 02 sensor after the cat and that didn't solve anything and still have a check engine light. I've been lurking and searching like crazy and some sites doesn't state after the cat or before the cat...does it really matter, an 02 sensor is an 02 sensor no? Any help would be greatly appreciated!

Thanks,
Fred

What code are you trying to fix? Check engine lights mean nothing without knowing the associated code.

 

[T4R_Finally]

Have you had a scan to see which code(s) the cel is coming on for? Did you reset the cel after replacing the downstream sensor? Are you sure you installed the right sensor?

Just throwing sensors at a cel is "guessing".

 

[DC runner]

FYI:

Many local auto parts places sell Denso OEM sensors. I am a 4th gen owner, but I just had to replace an upstream sensor and saw that Denso is the OEM maker. So, just pick up a Denso at your local autozone or advance auto parts.

Mine was 85 ish bucks at Advance when the dealer wanted 140.

Also. When I had a O2 sensor go out on mine, I got a very clear code that pointed to which one. It told me which side (I have 2 on each exhaust branch) and which one (before or after cat). Hopefully the 3rd gen has similar helpings.

 

[TegoXR]

What code are you trying to fix? Check engine lights mean nothing without knowing the associated code.

Have you had a scan to see which code(s) the cel is coming on for? Did you reset the cel after replacing the downstream sensor? Are you sure you installed the right sensor?

Just throwing sensors at a cel is "guessing".

The infamous P0171, when I purchased the vehicle the previous owner told me it was the oxygen sensor and thats the reason why it had a check engine light. I scanned it a few weeks ago and got the P0171 code. I tried cleaning the MAF, it went away for a couple of weeks and then it came back.

 

[DC runner]

I hear rumor this code can pop from a weak fuel pump. If, after you clean MAF and replace sensor it is still there, that is another think to check. You can check the fuel pump pressure. A lean code can be caused by bad spark or not enough fuel.

Hope it is an easy fix.

 

[TheDurk]

Here is the official list:

Air induction system
Injector blockage
Mass air flow meter
Engine coolant temp. sensor
Fuel pressure
Gas leakage on exhaust system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
PCV valve and hose

http://www.ncttora.com/fsm/1996/SIL/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/di/eg5vzfe/cip0171p.pdf

I can guarantee you the after cat sensor, (Bank 1 Sensor 2) had nothing to do with it. In the spirit of cheap fixes first, after MAF cleaning, also clean your throttle body (this cleared mine ten years ago) and check for any air leaks in the induction system and also in the exhaust system (pre-sensor 1). Verify your PCV valve is in good shape.

If no joy, then bench test your MAF.here Sometimes they die and cleaning won't do it.

Only after all that would I invest in a new A/F sensor (in the absence of any other codes).

Good luck.

 

[Christopher1]

Hi guys am newbie here and i have a 96 Concorde XL it want to start but it's not firing I change the cam sensor, crank sensor, battery, coil pack and check all the fuse under the hood and in the car but it still wont start can someone please help me?????

 

[2geauxin]

po171

I just spent 900.00 and still running rough when romped, I have a 2000 6cly TRD supercharged I was getting the lean bank{po171} and spark knock pretty bad. took to shop items checked and replaced were 1.both knock sensors,2. fuel filter,3. spark plugs,4. 1&4 cyl coil, 5. plugs, smoke test for vacume leak,cleaned MAF, compression check,fuel pressure checked??? at idle?? im not sure how you check pressure, Ok now,
It runs ok? normal drive but when u romp on it it really strts bucking and looses accel when you let off it returns to normal now when I say Romp i just mean passing gear even, the harder you romp the more it stumbles, the mech crimped the fuel return line and we drove it and the power was much better but still had a slight feel of power loss. where would you blow your money now?? or check. He thought maybe pump and sock?? and if so what brand pump or should i find out which plugs he put in?
someone PLEASE help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!