Can the wrong air/fuel ratio sensor cause p0171?

Hi forum,

Been fighting a p0171 for sometime on my 02 2.7L prerunner automatic 2wd. Did many of the simple things like cleaned MAF, replaced MAF, replaced PCV valve, smoke test for vacuum leak etc. Readings for the air/fuel ratio sensor for live data on my scanner seem normal and responding. However, I recently found that the air/fuel ratio denso sensor that I have on currently is the wrong "fit" for my prerunner. I've had that sensor since 2017 and it never showed any problems. You think this would cause my p0171?

Current INCORRECT denso sensor on my prerunner: 89467-35011
The CORRECT denso sensor for my prerunner: 89467-35050

 

Has the code been present since the sensor was replaced??

Just what is the 89467-35011 sensor listed to fit

 

Code was never present since the sensor was replaced.

The 89467-35011 fits the 2.4L and the 4X4 manual trans 2.7L. Everytime I put in my VIN number it shows this sensor does not fit my vehicle. But the 89467-35050 is a match for my truck. Even the Denso website says this, so it's weird to me.

 

I don't understand. You currently don't have a code? If not, don't mess with it. Do your LTFT look good? Leave it alone. Also, you sensor part numbers don't match anything I know about sensors. Check your part on Denso website. Your 02 is a wideband upstream and a narrowband downstream. As long as you have the right type, the different part numbers are just different lengths of wire. Check out this snip I pulled after I put in your truck info.

 

I do currently have a code. I thought he meant right after I replaced the sensor two years ago the code came up. The sensor has almost 20,000 miles on it.

Fuel trims are high and from live data I did monitor them go down when the throttle is open leading me to believe a vacuum leak but I did both a smoke test and sprayed around with carb cleaner and found nothing.

89467-35011 is an alternate part number for the sensor which is the

$147 Denso 234-9002 Air Fuel Ratio Sensor

Denso 234-9002 which is currently on my truck. 89467-35050 is

$143 234-9001 Upstream Air Fuel Ratio Oxygen Sensor with 10.6” 4-Wire Harness, for Auto Trans Equipped Vehicles

234-9001 which should be the one for my specific trim.

 

the correct sensor is too expensive to get and install as a test... do you have the old sensor still, if so, pop it in and see.
assuming no exhaust leaks.
was the questionable sensor purchased at the dealer or aftermarket? I have had situations where the aftermarket sensors are "compatable" but there is something just different enough to throw a code. Pop the old sensor in a code does not come back.
what are the STFT at idle? There is the possibility that you could have a "lazy" sensor and it reacting slower that the rear sensor might cause this code.
Best way to test for this is with propane enrichment. With an unlit propane torch find a vacuum line that has vacuum with the throttle closed and put some propane in the motor and watch the STFT for the upstream O2 sensor and see how it reacts and how fast it reacts, should be almost instant.
If the seal around the sensor, the hole that the sensor goes into is not perfect, this will fool the sensor into thinking the motor is lean.

very good write up.

https://parts.olathetoyota.com/air-fuel-ratio-sensors

 

The questionable sensor was purchased off eBay. So maybe it's not a legit denso sensor because I paid $70 for it new and the actual price is ~$120 or so. Thanks for the info and I'll check it out.

 

That could be it. I've heard of some crap sensors out there, even ones from a reputable retailer like rock auto aren't really all that good.

It's so hard to tell who the hell you're buying from with ebay or Amazon orders, which is why I try to avoid buying critical auto parts from those places. One exception would be that ebay seller that sells those timing belt kits with all factory OEM parts. There are tons of people here (me included) that bought kits from him and they've been nothing but superb.