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.
This part fits
10 vehicles spanning 1999-2004.
Fits these Makes
Select vehicle
Year
Make
Model
Description
1999-2002
Land Rover
Discovery
Land Rover Discovery V8 4.0L Upstream Left O2 Oxygen Sensor TRQ OSA61178
1999-2002
Land Rover
Discovery
Land Rover Discovery V8 4.0L Upstream Right O2 Oxygen Sensor TRQ OSA61178
2003-2004
Land Rover
Discovery
Land Rover Discovery V8 4.6L Upstream Right O2 Oxygen Sensor TRQ OSA61178
2003-2004
Land Rover
Discovery
Land Rover Discovery V8 4.6L Upstream Left O2 Oxygen Sensor TRQ OSA61178
2002-2004
Land Rover
Freelander
Land Rover Freelander V6 2.5L Upstream Right O2 Oxygen Sensor TRQ OSA61178
2002-2004
Land Rover
Freelander
Land Rover Freelander V6 2.5L Upstream Left O2 Oxygen Sensor TRQ OSA61178
1999-2000
Land Rover
Range Rover
Land Rover Range Rover V8 4.0L Upstream Right O2 Oxygen Sensor TRQ OSA61178
1999-2000
Land Rover
Range Rover
Land Rover Range Rover V8 4.0L Upstream Left O2 Oxygen Sensor TRQ OSA61178
1999-2002
Land Rover
Range Rover
Land Rover Range Rover V8 4.6L Upstream Right O2 Oxygen Sensor TRQ OSA61178
1999-2002
Land Rover
Range Rover
Land Rover Range Rover V8 4.6L Upstream Left O2 Oxygen Sensor TRQ OSA61178
Part Interchange
Brand Label
Part Number
Walker Products
250-24496
ACDelco
213-2909
VEMO
V48-76-0001
DENSO
234-4694
Wells
SU5577
Standard Motor Products
SG1709
VAICO
V48-76-0001
Niehoff
FE80894
Bosch
15175
Delphi
ES10895
DENSO
234-4695
Bosch
15184
Standard Motor Products
SG1706
Beck/Arnley
156-4398
Wells
SU5578
Niehoff
FE80891
TRQ
OSA61178
autopartsIn
WKK250-24496
Rover
MHK101100
Rover
MHK100920
Rover
MHK100940
This item may be interchangeable with parts from other brands with the above part numbers.
This information is provided only for reference and does not guarantee that the item you are
purchasing is identical to parts with part numbers from the brands listed above.
To confirm that this item fits your vehicle, use the above "Check Vehicle Fit" option.
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.
Product Reviews
5.0/ 5
★★★★★★★★★★
1 review
5★
100%
4★
0%
3★
0%
2★
0%
1★
0%
★★★★★July 23, 2018
Great prices and super Service and Customer Service....Thanks
I have been a customer for over two years and have had gr8 experience with one smooth return.
Keep up the great work.
I recommend this Auto vendor 1Aauto to all!
Thanks Ed
Showing 1–1 of 1 review
Customer Q&A
Got a question about this part? Post it and get answers from our team.
No questions have been answered for this product yet.
Customer service
877-844-3393
Monday - Friday 8:00am - 9:30pm ET Saturday - Sunday 8:00am - 4:30pm ET
Ask a Question
Check Your Email
We sent a verification email to .
Click the Verify Email button in the email to submit your question.
This extra step helps prevent spam.
Land Rover is a registered trademark of Jaguar Land Rover Automotive PLC. 1A Auto is not affiliated with or sponsored by Land Rover or Jaguar Land Rover Automotive PLC.See all trademarks.
Select Your Vehicle
Specify your vehicle's year, make and model to guarantee fit.