About TRQ: TRQ is a trusted brand dedicated to making every repair a success story by combining premium parts with easy installation. Each TRQ part is engineered by a team of automotive experts to meet or exceed OEM standards, delivering enhanced performance and maximum longevity. With rigorous in-house testing, the brand ensures superior fit and function across every product line. TRQ also provides customers with best-in-class, step-by-step installation videos—so you can complete repairs with confidence, whether you're a first-time DIYer or an industry professional.
Product Features
Application Specific Design: No modifications and pre-calibrated
Isotatic-pressed and plasma-sprayed for extended service life
Double-Layered 310S Stainless Steel: Additional protection from moisture and debris
Restored Engine Performance: Improved fuel economy and lower emissions
Description
TRQ oxygen sensors are manufactured to precise specifications using premium raw materials to optimize your vehicle’s emission system. Each sensor is isostatically-pressed for improved strength and durability, and plasma-sprayed to improve sensitivity and prolong the service life of the sensors. Oxygen sensors wear out over time and should be replaced every 60,000 miles to prevent poor engine performance. TRQ recommends replacing the oxygen sensors in sets to optimize fuel economy and reduce overall emissions. All products are fit and road-tested in our Massachusetts R&D facility to ensure we deliver on our promise of Trusted Reliable Quality.
What is Upstream vs. Downstream?
Upstream location is between the catalytic converter and the engine
Downstream location is between the catalytic converter and the tailpipe
Install Tip: You may be required to reset the vehicle computer after installation of this part.
Returns: Parts with electrical components cannot be returned once installed.
Attention California Customers:
WARNING: This product can expose you to chemicals including Lead and Lead Compounds, which are known to the State of California to cause cancer, and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov.
Lifetime Warranty
This item is backed by our limited lifetime warranty. In the event that this item should fail due to manufacturing defects during intended use, we will replace the part free of charge. This warranty covers the cost of the part only.
Returns: Parts with electrical components cannot be returned once installed.
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Expedited is available on checkout to the United States, excluding Alaska, Hawaii and US Territories as well as P.O. Boxes and APO/FPO/DPO addresses. Final shipping costs are available at checkout.
O2 Sensors is it Upstream or Downstream
How to Replace Front Exhaust Cross Pipe 2005-09 Subaru Outback
Created on:
Tools used
No Tools Needed
1. Identifying your Oxygen Sensors
Upstream oxygen sensors are located in between the engine and the catalytic converter
Downstream oxygen sensors are located in the catalytic converter or farther away from the engine than the catalytic converter
Locate your vehicle's firing order diagram
The bank that contains cylinder one is bank one
The bank that does not contain cylinder one is bank two, even if it does not contain cylinder two
Hi, I'm Mike from 1A Auto. We've been selling auto parts for over 30 years. We're dedicated to delivering quality auto parts, expert customer service, fast and free shipping, all backed by our 100% satisfaction guarantee. Visit us at 1AAuto.com, your trusted source for quality auto parts.
In this video I have a couple of oxygen sensors with me. While there are some aesthetic differences here, the wire lengths are a little different, the actual body and tip of the sensor are a little different, the threads and gasket are the same, and on the other end the connections are actually the same. I can plug these into either position on our vehicle. But if I had to ask you which one's upstream and which one's downstream, you probably can't tell just from looking at them. That's true of most oxygen sensors. The way you determine whether or not an O2 sensor is upstream or downstream is all done visually.
Your oxygen sensor position can be determined relative to your catalytic convertor. As the name suggests, upstream sensors will be located upstream or ahead of, in front of, above, closer to the engine than your catalytic convertors. This means that they see the exhaust gasses first. They then go through the catalytic convertor and to the downstream oxygen sensor, which will either be located in the catalytic convertor like our vehicle here, or after the catalytic convertor to monitor the gasses coming out of the cat and make sure that it's being efficient relative to the readings of the upstream O2 sensor.
The other determination you need to make is bank one versus bank two. Determining which bank is which can be done by looking at a picture of your vehicle's firing order. Whichever bank contains cylinder one is going to be bank one, and the other one, regardless of whether or not cylinder two is in it, is going to be bank two by default. These banks are true of V engines like V8s, V6s, and flat engines like Porsches and Subarus that have individual banks.
On inline four-cylinder engines, as long as they have one exhaust manifold like a Jeep four-liter or a four-cylinder Honda engine, you'll only have one bank with an upstream and downstream O2 sensor. There will be no bank two on the engine.
On our vehicle here, this is the passenger side, which we've already determined from the firing order is bank one. We have our upstream sensor here closest to the engine ahead of the cat. Then we have our downstream or sensor two here inside of the catalytic convertor. This could also be located somewhere after the cat. Here I have my two sensors for the vehicle. While they are aesthetically different, we can now tell this is my upstream sensor because it looks just like the upstream sensor I have up there. This is my downstream sensor. Now that we know which one's which, we can order the right part, correct the problem, and fix you up right.
Thanks for watching. Visit us at 1AAuto.com for quality auto parts, fast and free shipping, and the best customer service in the industry.
Tools used
Socket Extensions
14mm Socket
Pry Bar
O2 Sensor Socket
17mm Socket
Jack Stands
Ratchet
Floor Jack
Needle nose pliers
Wire Cutters
OSA61749
In Stock
Product Reviews
4.2/ 5
★★★★★★★★★★
12 reviews
5★
58%
4★
25%
3★
8%
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8%
★★★★★October 13, 2025
Works Great!!
I recently purchased an O2 Oxygen Sensor from 1A Auto, and I am beyond satisfied with both the product and the overall shopping experience. The quality of the sensor is outstanding-it fit my vehicle perfectly and has significantly improved its performance. Since installing the new sensor, my car's fuel efficiency and engine responsiveness have noticeably increased.
One of the best parts of purchasing from 1A Auto is their unbeatable pricing. The O2 Oxygen Sensor was affordably priced compared to other suppliers, allowing me to solve my car's issue without overspending. This great value combined with the high quality of the part makes 1A Auto a fantastic choice for any automotive needs.
What truly sets 1A Auto apart is their stellar customer support, particularly their instructional videos. The step-by-step guides provided for installing the O2 Oxygen Sensor were clear, detailed, and easy to follow. These videos took the stress out of the installation process and ensured that I could
★★★★★January 3, 2025
I love trq
Works great! It's been in my car for around five years without an issue
★★★★★January 1, 2025
Everything went as expected. 1A Auto took back the O2 sensor that i bought that was wrong. My fault and they did not charge me a return fee. Sweet!!
★★★★★March 19, 2024
2010 Subie O2 replacement
Still getting the O2 DTC after replacing both sensors with TRQ parts. Wish I would have spent the few extra bucks for the OEM. No heat shields or clips on the TRQ. Part is probably okay, I just have a new/different problem now. 1A is a good company.
★★★★★October 23, 2023
Best in class for auto repairs.
I did not use this product but requested a return. A1 was very responsive in helping me with my return. I am waiting for an email to finalize the process. This company is first class in support as well as products thus far. I will continue to use this company for my automobiles. No fault to the product or the company I decided to not install the item. it was my decision because I thought it was too difficult for me. This did not stop the company from granting my return and refund.
★★★★★September 20, 2023
As advertised
Easy to replace, right size. Passed emissions test next day and fuel economy increased
★★★★★October 31, 2022
It was a challenge to remove but we managed to do itSo far everything works OK the only thing strange is the alarm keeps going off when I close the trunk
★★★★★October 10, 2022
Only giving it a 4 because I just put it on so want to give it time but so far works great.
★★★★★July 12, 2020
DO NOT BUY THIS SENSOR!!!!
Sensor failed shortly after install. The pin configuration does not match the stock connector!! You will not be able to reinstall your factory sensor after using this sensor!!!!!
★★★★★June 30, 2020
Subaru O2 sensor
Exact fit
No issues with product
Getting the old one off is another story
Keep the videos coming
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WARNING: This product can expose you to chemicals including Lead and Lead Compounds, which are known to the State of California to cause cancer, and birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov.
