Upstream vs downstream o2 sensor. BAD downstream O2 sensor voltage chart.

• Upstream vs downstream o2 sensor Upstream vs Downstream. Did I read that right? Anyway, after hours of reading and watching youtube videos, it appears that my catalytic converters are bad based on the sensor data. Find out their locations, signal outputs, diagnostic codes, lifespans, and advantages. Upstream oxygen sensors can cost between $15 and $70. . the code should tell which one should be checked. Denso's description of the two sensors is exactly the same though, at least on the RockAuto web site. Nov 7, 2024 · Excess fuel in the system caused by a bad upstream O2 sensor can overwork the engine, leading to overheating. Some companies use different quality for the downstream to lower price, but definitely you can use the "upstream" sensors in both places. This sensor is doing its job and does not need to be replaced. It won't affect afrs. com Apr 19, 2023 · Learn the differences between upstream and downstream O2 sensors in terms of location, function, sensitivity, and design. The upstream air/fuel sensor has fewer ports for sampling the exhaust and also the shorter wire. Video of both upstream and downstream installation . If you're having fuel issues in closed loop it is likely your front o2 sensor. 79: $0. For precise information on the expected O2 sensor voltage range for a specific Jan 16, 2008 · The computer does a simple calculation (upstream O2 value - downstream O2 value). Learn the difference between upstream and downstream oxygen sensors, their location, function, readings, and how to identify a bad one. A main dealer can charge you up to around £150 an hour's labour to fit new O2 sensors, so this is a job well worth doing yourself Aug 14, 2008 · On the '01 Grand Caravan Sport, which O2 sensor is "Sensor 1 Bank 1"? Is it the upstream one at the manifold or the downstream catalytic converter? I'm getting "the following code: P0135" O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)". Nov 28, 2023 · Learn how upstream and downstream O2 sensors monitor and regulate the air-fuel mixture in your engine. I believe the difference also depends on the manufacturer because the Ford and Bosch sensors are offered with two different wire lengths and 2 different part numbers, but the Duralast sensors are only offered with the longer wire length and a single part number. Unlike the “upstream” O2 sensors that are located in the exhaust manifolds to monitor the engine’s air/fuel ratio, the downstream O2 sensors are used primarily to monitor the operating efficiency of the catalytic converter. the upstream and downstream sensors do different things. Mar 28, 2024 · The downstream sensor is a heated oxygen sensor and reads the emissions after the catalytic converter, while the upstream sensor is crucial for monitoring the air-fuel ratio in the engine. The downstream sensor is oxygen sensor 2. The electronic control unit (ECU) then uses this information to adjust the air-fuel mixture. e. Additionally on that thread is a recommendation for a sensor offset socket and a thread chaser to clean the O2 sensor holes. 4 %âãÏÓ 1 0 obj >>> endobj 2 0 obj >stream 2020-05-29T12:55:47-05:00 2020-05-29T12:55:53-05:00 2020-05-29T12:55:53-05:00 Adobe InDesign 15. Downstream O2 Sensors: What’s the Difference? Your vehicle likely has both upstream and downstream O2 sensors. Therefore, in an in-line 4-cylinder engine, the Nov 3, 2023 · Gain clarity on the differences between upstream and downstream O2 sensors. to/c/72/4/oxygen-sensorsIn this video, 1A Auto shows you how to identify an upstream or downstream oxygen ( Jul 31, 2020 · Hi guys, I've been lurking on this forum for a little while but this is my first time posting! I recently got a 2005 3. Air Nov 21, 2014 · Corvettes having four O2 sensors are using the two mounded post catalytic converter (downstream O2 sensors) to monitor catalytic converter efficiency. Test Example - In the example the downstream sensors are clearly cycling much less frequently than the upstream sensors, so this converter is in good condition (as far as the monitor can Jul 17, 2018 · Upstream sensor is air/fuel, downstream is o2 for reference. 00 There are bank 1 and 2, upstream and downstream, total of 4 o2 sensors, damn SULEVS are a nightmare. Feb 15, 2023 · The sensor number tells us where on the exhaust system the O2 sensor or the exhaust temperature sensor is installed. Tools & Materials List You can do this with a Scan Tool or a Lab Scope. 7l Liberty. B1S2 would be downstream sensor on the rear bank, and so on. A typical in-line 4-cylinder engine has only one bank (Bank 1). They play a crucial role in ensuring that the engine is running at optimal efficiency and producing fewer emissions. I am needing to replace my upstream O2 sensor (my cel comes on during highway driving complaining). Professional vs. An oxygen sensor that reports a lean fuel mixture, for example, will certainly set off a code. Feb 21, 2023 · Upstream Vs Downstream O2 Sensor. Downstream Upstream Oxygen Sensors Sep 19, 2023 · Is there a difference between upstream and downstream O2 sensors; Upstream oxygen sensors optimize engine performance by monitoring the air-fuel mixture before the catalytic converter, while downstream oxygen sensors assess the efficiency of the catalytic converter in reducing emissions. Downstream. May 16, 2016 · Good day. Upstream Oxygen Sensor Price. 0 (Macintosh Mar 20, 2011 · Upstream vs Downstream O2 Sensors Jump to Latest 9. Mar 5, 2017 · What does upstream and downstream mean? Simple, upstream means the O2 sensor is "upstream" of the catalytic convertors, meaning before the catalytic convertors. Downstream O2 Sensor (Bank 1 Sensor 2) O2 sensor 2 can also be called the downstream O2 sensor or bank 1 sensor 2. Explore their functions, locations, and how they contribute to maintaining a well-tuned engine. Professional O2 Sensor Sep 13, 2021 · The front oxygen sensor or air fuel ratio sensor is installed before the catalytic converter; it's called an 'upstream' or 'Sensor 1'. rectangular. downstream. As the volume drops May 27, 2012 · Measure between pins 1 & 2 and it should be 11 to 16 Ω at 20C. Use the following information to help diagnose the underlying problem. Jul 3, 2014 · The downstream one it just verifies that the catalytic converter is still functional. Apr 28, 2021 · I installed a downstream O2 sensor not long ago, and it looked the the one in post #4, i. It is what tells your cars ECU when the AFR goes rich, stoic, or lean. Front can be o2 or "afr" sensor, both of which are o2 sensors, narrow and wideband respectively. Read Also: Upstream Vs Downstream Oxygen Sensors. Hope that Jun 14, 2014 · About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright Feb 25, 2012 · My Rav4 is throwing a code for the Primary O2. 25A (at 0. If your engine frequently overheats, checking the upstream O2 sensor may help identify the cause. Shop for New Auto Parts at 1AAuto. Jan 2, 2011 · So I was thinking if I can swap the oxygen sensor for the front and rear banks, and see if the problem follows to the other bank. What brand of O2 sensors should I use for replacements? Nov 8, 2008 · As far as I know, the sensor is the same but the length of the harness wire is longer on the upstream sensors. I’m double checking what I bought at Auto Zone for my 2005 Mazda Tribute. ' Upstream sensor installation instructions here. It covers their locations and functions in maintaining a May 30, 2006 · The downstream O2 sensors are located just behind the catalytic converter, or on some Fords, in the converter itself. Generally, if we are talking about O2 sensors: Sensor 1 = Before Catalytic converter Front (Upstream O2 sensor) May 12, 2017 · The way you determine whether or not an O2 sensor is upstream or downstream is all done visually. You can use a good scan tool to graph them in action and determine if they're doing what they're supposed to do within spec. I just wanted to check with you guys to see which is which. ) Ford only appears to list one part number for O2 sensors. Gain clarity on the differences between upstream and downstream O2 sensors. The upstream sensor is the O2 sensor 1, located between the engine and the catalytic converter. Since we covered bank 2 sensor 1 upstream or downstream, let’s now take a look at the difference between these two The upstream oxygen sensor is located before the catalytic converter and is used to help calculate the air fuel mixture, and is often referred to a air fuel sensor. I saw that the 2 sensors wire pigtail are different, so I am not sure the 2 sensor are the same. Upstream sensors, located closer to the engine, regulate the air-fuel mixture by providing feedback to the engine’s computer. Now, you must be wondering what upstream and downstream sensors are. At AmericanTrucks, we offer oxygen sensors designed with special technical ceramics to provide “wideband” oxygen detection. The upstream rear bank sensor on our '06 was a real bear to get at, even worse than on our '08 AWD. What I am wondering, besides the cable length: Is there any difference between an upstream (before cat) and downstream (after cat) O2 sensor? Are the Sep 14, 2023 · Motorcraft doesn't make the upstream o2 sensor for my 2006 mustang gt anymore but says the downstream o2 sensor will work. More critical function means higher cost: Parts & Labor: $150 – $400+ Downstream O2 Sensor Replacement. Which sensor, upstream or downstream, REALLY is responsible for engine performance, meaning fuel trims, air fuel ratios? I suspect ONLY the upstream (precat) does that, but some people say the downstream ALSO adjust air fuel mixture Jun 12, 2018 · Description says will fit both upstream & downstream on 2008 Jeep Wrangler Unlimited (JKU), however the JKU uses different sensors upstream vs downstream as noted by the different type connectors on each. Dec 27, 2024 · Upstream vs. Nov 5, 2015 · Missing upstream sensor Hi, I would also like to replace the oxygen sensor on my 2003 corolla. The downstream O2 sensor checks the catalytic converter’s efficiency and helps keep emissions in . 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. Dec 31, 2019 · The rule of thumb for a fuel-related misfire concern is STFT going more than 15 percent positive, often into the mid 20 percent range or more and the downstream O2 voltage below 350mV. Jeep parts manual shows 56041212 1 ER0 Before Catalyst with 18" Pigtail (upstream) 56041213AB 1 EP0, ER0 After Catalyst with 12" Pigtail (downstream) Apparently the same o2 sensor is used for up and downstream except for the length of Symptoms of a Bad Oxygen Sensor. Accurate diagnostics of upstream and downstream sensors are essential for technicians to provide reliable, cost-effective repairs. So the math as I see it: If (upstream O2 value - downstream O2 value) = a negative number, than one of the sensors is bad. Jun 24, 2022 · If you’re wondering how to tell the difference of upstream vs. (Assuming same heater for the upstream O2 sensor) Possible DTCs P0135 - Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) or P0141 - Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) * Heater current is less than 0. The rear oxygen sensor installed after the catalytic converter is called 'downstream' or Sensor 2. I figured the downstream sensors can wait until they throw a code since they're just there to monitor cat performance. Sep 3, 2022 · So, we learned bank 2 sensor 1 upstream or downstream and we know that this sensor is upstream. I've done some light maintenance on it and the O2 sensors are next on my list. ) B1S1 would be bank 1 sensor 1. Nov 28, 2021 · This information monitored by the upstream sensors is then sent to the ECU where it is processed and used for regular fuel/air delivery. Switch it with the other side that has the original one in it and it works. Now, What should you do if the downstream O2 sensor is bad? An unnormal downstream voltage chart could be a symptom of a large range of issues. com http://1aau. Obviously, the upstream valve is always a higher valve. Telefon: +(86)15161516705 Mar 23, 2010 · Left and Right are the same. However, upstream and downstream oxygen sensors are Nov 16, 2022 · Otherwise, look for these signs of a bad oxygen sensor. Since a chemical reaction takes place, there is less O2 exiting the Cat. Meanwhile, downstream O2 sensors monitor oxygen content just like the upstream sensors. Correspondingly, Bank 2, sensor 2 is located downstream or behind the catalytic converter. On the V6 the upstream pigtails are slightly different (12. This increased vulnerability is due to its proximity to the combustion process, where it is constantly exposed to extreme temperatures and fluctuating exhaust conditions. The upstream sensor monitors the level of pollutants in the engine's exhaust and sends this information to the ECU that continuously adjusts the air-fuel ratio. Teléfono: +(86)15161516705 Mar 10, 2025 · Automotive oxygen sensors (O₂ sensors) are critical components ensuring vehicle performance, fuel economy, and emissions compliance. 電話: +(86)15161516705 We would like to show you a description here but the site won’t allow us. The 1st sensor is located closest to the engine, and the last is located toward the rear of the exhaust system. Find out the functions, differences, and common problems of each type of sensor. You must replace all o2 sensors at the same time, this is highly recommended, when you only change one the debris from exhaust will be read differently then the other sensors and can cause a myriad of issues with bmws because of their overkill Jul 1, 2022 · I was following and referring to the thread of info that had a picture of where the different Banks and Sensors are and what is upstream vs downstream. Oct 17, 2007 · Their parts lookup for O2 sensors also gives different part numbers for upstream/downstream sensors. May 28, 2015 · That is true for your model year. Jan 15, 2023 · If you’re a car owner, you may have heard of the term “O2 sensor” and wondered what it does. Dec 8, 2021 · I changed out the upstream O₂ sensors (aka A/F sensors) on our '06 and '08 earlier this year. In this article, we’ll explain in detail what a downstream o2 sensor is, its role in your vehicle, and why it May 16, 2017 · I have a 98 XJ that uses an up and downstream o2 sensor. If you’re looking to improve fuel efficiency or reduce emissions, Summit Racing has the Oxygen Sensors (o2 Sensors) to improve your vehicles performance. Just because a fault code indicates an oxygen sensor problem, don't just replace the O2 sensor. Generally, O2 sensors are installed in the exhaust system to monitor the level of harmful pollutants in the emissions being passed from the engine’s combustion chamber to the exhaust’s tailpipe. Choose from Narrowband, Wideband, Upstream or Downstream O2 sensors. On the J35 engine that will be the upstream sensor on the rear bank. On Denso's website they list an Upstream and Downstream sensor. These O2 sensors operate just like the low The upstream O2's monitor your fuel trim, while the down stream O2's just monitor the cats to see if they are working correctly. So any O2 sensor problems have to be dealt with before you can use the OBD II system to diagnose the Most vehicles today are outfitted with at least two O2 sensors, an upstream and downstream sensor and one for each exhaust manifold, that help maintain vehicle emissions and fuel economy. The downstream oxygen sensor, also known as Sensor 2, is positioned after the catalytic converter. Role in Fuel Mixture Nov 3, 2023 · These sensors are classified as “upstream vs downstream o2 sensor,” based on their location relative to the engine and catalytic converter. Aug 27, 2024 · Fortunately, locating the specific oxygen sensor isn’t as hard as it may seem. You may run into a situation where the catalyst monitor won't run because there's an O2 sensor code. Then shop at 1A Auto for a high quality Oxygen Sensor replacement for your car, truck, SUV or van, at a great price. Maybe I had replaced it long ago also. Nov 3, 2023 · Gain clarity on the differences between upstream and downstream O2 sensors. My PERSONAL experience is that I buy the ones with the best warranty because EVERY TIME i go wheeling and drop into some water (deep enough to cover the exhaust) I burn up my O2's. For each 10 upstream sensor signal switches the downstream sensor signal should switch less than 7 times. The upstream O2 sensors are the important ones just make sure to use the same brand with them, Downstream is not nearly as important. That is because Bank 2 is the side with the engine’s second cylinder, and Sensor 2 acts as a downstream spot. Oxygen (O2) Sensor Thread Repair Bank 1 Sensor 1; Bank 1 Sensor 2; Downstream; Upstream ULTRA-POWER 25024154. The downstream sensor is a heated oxygen sensor and reads the emissions after the catalytic converter. While the part itself is not super expensive, the installation usually costs more than Jan 6, 2023 · The upstream O2 sensor regulates the ratio of the fuel mixture by flip-flopping between rich and lean mixtures. 1A Auto has a large selection of aftermarket O2 Sensors for many makes and models, including Upstream (Front) Sensors, Downstream (Rear) Sensors, and more. Similarly, downstream O2 sensors monitor the level of unburnt oxygen (pollutant) in the emissions released by the catalytic converter. Sensors simply report information. The 4 they sent all have same connectors and nothing indicating which is up or downstream. Now let’s take a look at the difference between these two sensors and how they differentiate. The upstream sensor, also known as the primary sensor, provides vital feedback to the ECU, enabling it to adjust the air-fuel mixture for optimal combustion. the upstream sensor is in front of the cat and the downstream sensor is after the cat. downstream O2 sensors and how to find bank 1 or bank 2 of your car, check out the tips from our expert mechanic in this article and video. Unfortunately I can only find the downstream oxygen sensor under the car on the exhaust pipe. Oct 18, 2024 · Which O2 Sensor Goes Bad First: Upstream or Downstream? Typically, the upstream O2 sensor is more prone to failure than the downstream sensor. %PDF-1. Controls air-fuel ratio. Jul 8, 2012 · Rear sensor is only to monitor cat efficiency. It is in charge of determining the composition of raw exhaust gases. The OBD II system can't evaluate the converter if the upstream and downstream O2 sensors are not functioning normally. 핸드폰: +(86)15161516705 Nov 28, 2021 · Oxygen sensors (also called O2 sensors) are typically four in every modern vehicle; 2 upstream O2 sensors and 2 downstream O2 sensors. This allows the catalytic converter to lower emissions by keeping the average ratio of the fuel mixture in proper balance. It looks like your cats are bad, the post cat sensors are all over the place and they should be mostly steady when in closed loop. After reading through the service manual, the upstream sensors are called HO2S while the downstream sensors are called Catalyst Monitor Sensors. Also, should I assume the O2 sensor needs Nov 23, 2024 · Faulty O2 sensor, Air leaks, or Clogged exhaust system: 0. See full list on bryansgarage. I believe the big difference in price is upstream vs. I've seen some mentions that the upstream and downstream sensor are the same part on Mar 10, 2021 · Function — Upstream oxygen sensors primarily monitor and adjust the air-fuel mixture, while downstream oxygen sensors evaluate the efficiency of the catalytic converter. The upstream sensor, located before the catalytic converter, measures the oxygen content in the exhaust gases directly from the engine. $30. The front o2 sensor is how your engine reads and adjusts closed loop fuel trims. Oxygen (O2) Sensor Socket / Wrench. I ordered 2 new Motorcraft sensors, then realized there are 4 on the car. I'm hoping you guys can help me with a doubt. The guy said the wire in the 15718 is longer than the 15716 (or vice versa, I forgot which is whicih right now), and also they don't both have the same number stamped into the actual sensor (minus a secondary number which was different on each of the one I bought, possibly a serial number that is). Impact on Diagnostics — Upstream oxygen sensors provide critical data for immediate engine performance adjustments, whereas downstream oxygen sensors assess and ensure the May 30, 2006 · The downstream O2 sensors are located just behind the catalytic converter, or on some Fords, in the converter itself. Jan 4, 2024 · The oxygen sensor is an item in a vehicle that gets replaced due to the fault of another component. Customer: Is there a physical difference between the downstream oxygen sensor and the upstream oxygen sensor? I’m double checking what I bought at Auto Zone for my 2005 Mazda Tribute. After understanding the role of the upstream oxygen sensor near the engine, you can now explore the downstream oxygen sensor‘s location in your vehicle’s exhaust system. The downstream oxygen sensors also can be also used in a similar fashion to analyze concerns such as a fuel pump losing pressure or volume. But, rock auto has listings for both up and downstream. Upstream VS Downstream O2 Sensor. Here we’ll show you the difference between a bank 1 sensor vs a bank 2 sensor along with upstream vs downstream O2 sensor locations. Understanding Oxygen Sensors: Upstream vs. I've replaced the o2 sensor with three different Motorcraft part #dy-1401 and I get the code that says slow response from that o2 sensor evertime. The cost of an upstream oxygen sensor will depend on what vehicle you own. My Element is a 2005 and I have owned it since new. Find out how to diagnose and replace faulty sensors and why they are important for your vehicle's performance and emissions. The O2 sensor I removed was Denso 234000-7100. The drastic temperature change will kill them. Each sensor – upstream or downstream – is designed specifically, even though they perform the same similar function. More so, the threading pattern of these sensors differs; while upstream sensors thread into your exhaust manifold, downstream sensors thread into the catalytic converter Car Electronix Oct 23, 2024 · Upstream vs. Feb 21, 2024 · Function of Upstream O2 Sensors. If it does, then the sensor is bad. Upstream O2 Sensor Replacement. Downstream means the O2 sensor is "downstream" of the catalytic convertors, meaning after the catalytic convertors. If your car has upstream and downstream O2 sensors, the latter tends to be more accessible and the job and should take a home mechanic under an hour. Downstream Oxygen Sensor Location. My guess is primary O2 = Upstream (before cat) and downstream = secondary O2 (after cat) Thanks Dec 9, 2023 · Upstream vs. Downstream O2 Sensors Understanding the difference between upstream and downstream O2 sensors is key to diagnosing and troubleshooting potential issues. I believe the Denso O2 sensor was original, but I'm not certain. Jul 20, 2016 · I just called a different advance auto, and I DID get the wrong ones originally. 2" and 13") but you can use a 13" in both places. Find product recommendations and tips for maintaining your car's exhaust system. Sep 16, 2008 · Alright, now I have a question. Symptoms of a Bad Downstream O2 Sensor. Nov 28, 2021 · So, what are the bad downstream O2 sensor symptoms that show the sensor is failing? Generally, a failing O2 sensor (whether upstream or downstream) would trigger the check engine light to illuminate on the dashboard. And of course the upstream sensor is more expensive. 3 second after heater is turned ON) Jan 22, 2013 · sensor elements are the same, wires are different lengths. DIY O2 Sensor Replacement. But the average cost of this part is $35. Learn how upstream and downstream O2 sensors monitor oxygen levels in your car's exhaust system and optimize combustion. If (upstream Apr 12, 2019 · On this video I will explain the difference between the upstream and downstream oxygen sensors on your car, specially when you order it from the part store t This video explains the key differences between upstream and downstream oxygen (O2) sensors in cars. Additionally, the threads and wire lengths of these sensors are different, preventing them from being swapped out. Upstream O2 sensors, also known as pre-catalytic converter sensors, are located before the catalytic converter in the exhaust system. Your oxygen sensor position can be determined relative to your catalytic convertor. O’Reilly Auto Parts stocks the right tools and parts, including O2 sensor sockets, and replacement upstream and downstream oxygen sensors to help you repair your car, truck, or SUV in no time. Visit us online or call 888-844-3393 and order your Oxygen Sensor today! Jun 5, 2013 · bank 1 is against the firewall and bank 2 is against the radiator on our v6. Nov 16, 2021 · Read Also: Upstream Vs Downstream Oxygen Sensors. In that case, you will have 2 upstream and 1 downstream sensor. 2006 Super Black Xterra "S" 5AT 4x4 Oct 9, 2024 · For some cars, there can be even 3 sensors for one exhaust system, up to 6 sensors in total if the engine is V-shape. If the problem remains in the same bank then the catalytic converter is bad. Nov 15, 2021 · With the explanations above, it is easy to detect the difference between these two types of oxygen sensors; one sits at the front of the CAT while the other sits after the CAT; the position of O2 sensors is the major difference between “upstream” O2 sensors and “downstream” O2 sensors. Oct 7, 2023 · Here’s the comparison of the GOOD vs. Téléphoner: +(86)15161516705 Feb 1, 2013 · O2 SENSOR DIAGNOSIS. Apr 30, 2019 · The upstream oxygen sensor is situated before the catalytic converter whereas the downstream oxygen sensor is located after the catalytic converter. The O2 sensor is an essential component of your vehicle’s exhaust system and helps monitor how efficiently your engine is running. It is first important to understand that an OBDII code in itself is not indicative of a failed oxygen sensor. GOOD vs. Aug 21, 2008 · Like oxygen sensors, though, air/fuel ratio sensor will be positioned before and after the catalytic converter on OBDII-compliant engines (Sensor 1 is always on the exhaust manifold, Sensor 2 is always after the catalytic converter) and will be referred to as O2 sensors in most of the OBDII literature, despite being air/fuel ratio sensors. But you can try some useful tips below to eliminate the code: First May 17, 2011 · Upstream Sensor is in the Exhaust Manifold Pre-Cat Downstream Sensor is in the Exhaust Pipe Post-Cat Second difference: (and most important) There is a reason why the Upstream O2 sensor is about 2-3x more expensive than the downstream sensor. Less integral to core engine operation: Parts & Labor: $100 – $300. There is no oxygen sensor underneath the heat sheild next to the fire wall. BAD downstream O2 sensor voltage chart. sometimes its not the sensor but the wiring though its difficult to tell. (2 Upstream and 2 Downstream. 7K views 7 replies 5 participants last post by Jeff K Mar 23, 2011 Mar 2, 2023 · When it comes to oxygen sensors, cars typically have one of two types: the upstream, or primary O2 sensor, and the downstream, or secondary O2 sensor. They both function the same but are different enough that they cannot be swapped. I removed the heat sheild to make sure I was not missing it. It looks like you can find the NTK(Denso/NGK) O2 sensors that don't require any splicing for around $40 each online with connectors. Replaced with NTK 24631. If you have fried secondaries or fried primary sensors I would just move the good ones to the primary and stick a resistor into the plug on the rears to fool the ecu into thinking the secondary o2 sensors are still good. Though the readings taken are quite different. 5-2% Oxygen (10-12 Volts) O2 sensor readings fluctuate: Faulty O2 sensor, Fuel pressure issues, or Faulty ECM: Nov 3, 2023 · Gain clarity on the differences between upstream and downstream O2 sensors. An upstream O2 sensor detects oxygen content so that the computer can adjust the fuel injector pulse width to improve fuel economy and ensure that the engine runs properly. Later years' sensors are distinctly different. Monitors emissions. Dec 19, 2022 · I plan on replacing the O2 sensors while the exhaust is off. This information is used to adjust the air-fuel ratio. Jun 4, 2020 · If you are here because you have a bad heater in the downstream sensor, personally I'd ignore it until the sensor gets 'lazy. Denso 2003-2008 FWD Upstream, Direct fit Denso 234-9052 which averages $88 on Amazon Upstream Universal N/A Oxygen sensor replacement is normally a straightforward job. Primary O2 Sensor (upstream) The upstream O2 sensor is usually located before the catalytic converter close to the exhaust manifold and monitors the amount of oxygen in the exhaust gas. May 30, 2022 · The car seems to run good otherwise. Dec 17, 2018 · Sensors are referred to as Bank X Sensor X where the bank number is as described above, and the sensor number has to do with upstream (sensor 1) and downstream (sensor 2. Mar 10, 2018 · Robert, if you want to keep good tabs on the condition of the cats, make sure those downstream O2 sensors are working good. ccs cqnb veseqk ejcp noi chfp ymxworpy nddqzf jqt jea xtf xvd ruktk srqv kuts