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.
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
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.
Quality Tested - built to a strict level of product standards.
Item Condition:New
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.
FREE Shipping is standard on Orders shipped to the lower 48 States (Contiguous United States). Standard shipping charges apply to Hawaii, Alaska and US Territories. Shipping is not available to Canada.
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
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.
OSA61248
In Stock
Product Reviews
Loading reviews
4.58/ 5.012
12 reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star
10
1
0
0
1
The part did a very good job, Fixed check engine light, No problems, Would buy again, Good part at a good price.
E
July 29, 2019
I would would tell other people to buy from 1A AUTO, Thank you.
Perfect Fit
Kayla
October 13, 2019
Shipped faster than I thought. Fit perfectly and no issues. Awesome all the way around!
02 wrx o2 sensor
Daniel
October 24, 2019
I had a check engine light on for my downstream o2 sensor, i checked it and one of the wires was completely torn due to it touching the downpipe. I replaced it with this one and zip tied it out of the way of the down pipe and boom check engine light gone and did not spend alot of money.
Awesome!
Christopher
March 23, 2020
Exactly what I needed and cheaper than the local parts stores!
Great
Marcos
September 14, 2020
Great quality but it wasnt the one I needed but you guys switched it quick and I very much appreciate how quick you guys handled the situation
Noelle
April 21, 2021
quality part! arrived pretty quick. love this website will never go anywhere else
Spend the money Get a quality part
Weston
August 30, 2021
Doesn't work. Car runs worse with this then the old one. Tried to do a return but I will not let me. Unfortunately waisted my money
Best in class for auto repairs.
FRANK
October 23, 2023
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.
2010 Subie O2 replacement
John
March 19, 2024
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.
O2 sensor. you need this one and another one for before and after the Cat.
Jerry
July 26, 2024
have to buy two. same review for the other one.
O2 sensor
Steven
August 21, 2024
Perfect fit, quick to ship, and best price. What more could I ask for.
Satisfied
Nick
December 4, 2024
The O2 sensor replacement went smooth with this part and the code has not come back on. The part also came with the anti-seize lubricant applied, which was helpful!
Customer Q&A
What size socket is needed for removal of downstream O2 sensor?January 14, 2016
Chris O
10
7/8 socket
January 19, 2016
Gilbert B
10
Got this over a year ago unfortunately it never made it on the car because it got in an accident. 1A Auto even credited the item back to me. If my memory serves me right I found a video on Youtube that explained everything including what size socket to use
January 19, 2016
NICHOLAS C
10
O2 sensors take a 7/8 or 22mm wrench or 02 sensor socket.
September 5, 2017
Terry S
10
22mm = 7/8
Make sure you use a proper socket because the wiring will be weird
September 22, 2018
J Y
10
7/8
February 23, 2019
Derrick M
Is 5his,upstream fit?December 31, 2019
Dustin H
10
Hello and thank you for your inquiry! We'd be happy to look into this for you, but will need the year, make, model and engine size of your vehicle to determine if this is correct for the upstream or downstream position for your application. We look forward to hearing from you. Thank you!
January 2, 2020
Katie L
Is this an Upstream fit for 2004 WRX 2.0l?January 17, 2020
Carlos A
10
Yes, according to the information you provided, this will replace both the up and downstream sensors for a 2004 Subara Impreza 2.0L Turbo. Please let us know if you have any other questions!
January 17, 2020
T I
Will this work as an upstream sensor on my 2010 Subaru WRX? Essentially need to know if this sensor is heated.June 1, 2020
Zach S
10
Zach, thank you for your inquiry! This sensor would not work as an upstream on your application. In order to see if we offer the correct upstream sensor could you provide your 17-digit VIN? We look forward to hearing back from you!
June 2, 2020
Jessica D
How long is the wire length?September 23, 2021
Ricky R
10
Actual Measurements are not listed or available. Our parts are exact replacements for your vehicle's OEM parts. As long as your year, make, and model match up with our listing, these parts will directly fit and function like the originals.
September 23, 2021
T I
10
The length was generous compared to OEM on a 2007 Impreza, but nothing a zip tie couldnt handle. If youre looking for a truly extended wire, it is probably best to look at a different option.
September 23, 2021
James L
Will this fit upstream and downstream ? On a 2005 forester?January 16, 2022
Aramis R
10
Hello, this is listed for the downstream only.
January 17, 2022
Ricale A
Customer service
877-844-3393
Monday - Friday 8:00am - 9:30pm ET Saturday - Sunday 8:00am - 4:30pm ET
Saab is a registered trademark of Saab Automobile AB. 1A Auto is not affiliated with or sponsored by Saab or Saab Automobile AB.See all trademarks.
Enter Vehicle Year Make Model
Specify your vehicle's year, make and model to guarantee fit.
Year
Make
Model
Options
Drivetrain
This part doesn’t fit a . Select from parts that fit.