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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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.
Product Reviews
4.0/ 5
★★★★★★★★★★
25 reviews
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★★★★★February 13, 2026
Working great, solved my problem!
★★★★★January 26, 2025
O2 sensor change
This worked well and it was good changing it as a set.
★★★★★March 18, 2024
Works great,. Check engine light was on and I took a guess at the problem and ordered the sensor, took about 45 minutes to change out and the next day the check engine light turned off.
★★★★★November 26, 2023
O2 sensor
Had in for 2 weeks. Now check engine light is on for O2 heater circuit malfunction.
★★★★★November 17, 2023
Great product!
Works perfectly and cleared out my CEL!
★★★★★July 17, 2023
When cats bad loose factory 5,500 everywhere revs 500 revs 1000 at times
2001-2003 subaru outback limited 2.5I Baja legacy models what's weird I'll tell you every thinks everything's fine guess what it's odd actually check engine light off right A++ their the engineer made this car accidentally about that only 1 sensor I'll tell you that the cats will oddly strange keep working fine Houston we have a problem their not even though magically they are working too alot of mechanics out their post cat 1 is the fix
★★★★★May 1, 2023
Fit perfect and got rid of the check engine light
★★★★★March 10, 2022
O2 Replacement Sensor
Fit like a glove and fixed my problem. Delivered quick.
★★★★★January 13, 2022
Yes my experience was very good I am recommended 1auto because I find what need whiteout any problem and price is good of the products and whiteout shipping charges ????
★★★★★January 10, 2022
Faulty sensor
I wanted to wait a few days of driving my vehicle before reviewing this item and I am glad that I did; I have driven for about 100 miles or so and the CEL came on today. Checked it with my scanner and code P0030 came up. Sensor 1bank 1. That is the sensor that I just replaced, the one I bought from you. It is faulty so what do you propose to do to rectify this situation? I await your response.
Showing 1–10 of 25 reviews
Customer Q&A
Got a question about this part? Post it and get answers from our team.
DouglasFebruary 7, 2022
Will this work on a 2003 Forester x?
Yes, this part will fit your vehicle as long as you have a H4 2.5L Upstream.
Emma · February 7, 2022
ROctober 6, 2018
I want to know if this product fit 2005 civic ex?
This is able to fit if you have a L4 1.7L.
Emma · October 8, 2018
carlAugust 12, 2018
Will this after market sensor really work as the high price sensor for my2004 honda civic ex ?
Will this work for a 2004 Subaru Impreza RS?
John · May 19, 2022
Showing 1–3 of 3 questions
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