Denso 234-9120 Oxygen Sensor (Air and Fuel Ratio Sensor)

Some items I will buy the cheaper aftermarket knock offs but if you look at the failure rate of aftermarket fuel ratio sensors you may only have a matter of months before failure. So this sensor was overdue on my car with 200k miles. This is an OEM sensor so I expect years of life and thousands of miles. Already after installing the sensor my mpg has increased from 18.5 to 20 and with no more check engine light. The car also is running better than ever.

I bought this to fix a P1153 "O2 Sensor Circuit Range/Performance (High) (Bank1 Sensor1)" Check Engine Light code on a 2005 Subaru Outback XT. I interpreted this as the front O2 sensor voltage reading was stuck high. The engine had 121,000 miles and had been running on 3 cylinders for the last few thousand miles, so I wasn't surprised that it killed the O2 sensor.This Denso 234-9120 part came with a connector that plugged right into the engine harness connector. The silicone jacket was blue compared to yellow on the original sensor. It even came with two push-in wire ties that plugged into the bracket on the ignition coil. There was only a minor issue because the wire tie locations were off by about 10mm from the original, but it was easy enough to nudge them a bit by hand. The package also came with a small tube of copper anti-sieze compound - there's plenty there for at least 10 O2 sensors, so I'll hang onto it for the next time I need to work on exhaust bolts and nuts.It was surprisingly easy to get to the O2 sensor on the exhaust manifold, and should be similar on a WRX or Legacy GT. I just turned the front wheels all the way to the right, removed one plastic clip for the front underbody tray in the wheel well, and used 3 long extensions on an O2 sensor socket to get the old O2 sensor off. I didn't have to remove the wheel or jack up the car using this method.Before replacing the O2 sensor, my OBDII scanner usually showed the rear (unheated) O2 sensor voltage reading stuck at about 0.8V. But after replacing both O2 sensors (due to age and mileage of car), I can see that it changes between 0.2V and 0.7V while driving. The best part is no more Check Engine Light so I can finally get the car inspected.

Easier to replace than I'd expected, immediately fixed my P0031 errors and maybe has even helped with transmission shifts?Now, hear me out, I bought my 2004 XT from my mechanic, who'd been given it as a "mechanic's special" by a client with 230K commuting highway miles on it. It has always had hard (clunky) shifting between 2nd and 3rd, despite paying to rebuild the transmission by a separate shop.I believe that in the 3 years I've owned it, the front 02 sensor has been in a state of near-failure, causing the ECU and TCU to not be able to easily "agree" to a good shifting pattern. Recently, the car had begun throwing P0031 (and various other related codes) consistently, and going into re-learn mode on every drive, much to my annoyance when you stall a turbo, fuel-injected, automatic car trying to pull out of the grocery parking lot.With the pandemic still in full swing, I haven't been driving much, but the 30 minute job to swap the sensor seems to have cured all my codes, improved acceleration and response, and maybe even smoothed out the shift pattern.BTW RockAuto agrees that this sensor is a proper fit.

Works in my 05 sti put over 1k miles with it on now and no issues sense I swapped it in thanks

I have an 05 Legacy GT wagon 5-speed. My car was constantly running super lean or rich, no inbetween and stuttering quite a lot between 2-3K RPM while idling a little rough. Putting this in for the old upstream sensor immediately solved every problem I've had with my car since buying it in December 2018. Car runs like a dream now!I'd recommend also replacing/cleaning your MAF sensor and accelerator pedal sensor at the same time for a pretty dramatic change in the drivability of your car. My car gets much better fuel economy and runs smooth all the time. I'd also recommend disconnecting the negative battery terminal before you do all of this (takes maybe a couple hours to do all three) so when you reconnect the battery and start the car the ECU can re-learn how to idle and such.

Perfect in my 2006 STi. Fixed P0031 code for bad heater element but I swear the car idles and pulls a little better now than it ever has under my ownership.The old clips are a pain to remove from the harness bracket on the engine, but the new clips are positioned exactly correct on the new harness; fitment is perfect. Plus it came with a small tube of copper ant-seize which is nice.Used the TEKTON 47749 low profile O2 socket and it did a good job given the area is a little awkward.

Don't install because I did works in 08 GR STI.Just installed the second 9120 into my 2008 gr sti multiple pro tunes lasted almost five years. 22 mpg 400whpIt's also still listed on sensor website. STI.exe

My idle and cruise throttle response had started oscillating on my 2005 Subaru WRX STi.According to the Denso website, this is the appropriate part for this engine, equivalent to dealer part # 22641AA211 (which of course is more expensive), and that was correct. It is a ~30 inch length, which is exactly what is required and it appeared to be an exact replacement for the existing sensor. I saw no evidence that it was counterfeit.I replaced the part, and everything is now perfect. Maybe it'll improve my fuel economy a bit, but I have to say that I'm not holding my breath!

It worked and cleared the code

This is a perfect OEM replacement for a 2007 Subaru WRX - it even has the clips to attach it to the bracket that keeps the wire away from the exhaust header. Much cheaper than ordering from Subaru.

2005 Subaru Outback XT experiencing P0030 and P0134 codes. This front O2 sensor installed (passenger front) fixed the issue right away.

fits well on my wrx 2008 did not solve my p2097 check engine

Perfect replacement for my 08 subaru forester. Thanks!