ULTM8Z Posted October 4, 2009 Share Posted October 4, 2009 So I'm going to break down and buy three new O2 sensors. The car has one at each exhaust manifold and one downstream of the cats. My scanner is showing all three sensors basically stuck at one voltage (right around 700 mV) rather than bouncing back and forth like I'm used to seeing on my other cars. First of all, the car only has 45k miles on it. Would the factory O2 sensors fail that quickly? Nonetheless, as I'm browsing online I'm seeing sensors by Bosch and Denso ranging from $50 universal types to over $200 for what seem like more vehicle specific. What's the deal? Aren't these all just plain ol' narrow band heated sensors? Why the wide range in pricing? What exactly is needed? CAr is a 2005 RX330. Quote Link to comment Share on other sites More sharing options...
joe913 Posted October 5, 2009 Share Posted October 5, 2009 You might want to find which sensor is bad before you order. If you want a drawing/troubleshooting guide for the sensors, send me your email address. You will find page SF-75 demonstrates the procedure for diagnosis. The sensors are different than the ones you buy at the parts store. Some say you can buy a Denso and be just fine. I just purchased a LexusToyota A/F sensor for $145 on eBay. The sensors are easy to check by using an ohm meter. Good luck! Quote Link to comment Share on other sites More sharing options...
code58 Posted October 5, 2009 Share Posted October 5, 2009 You might want to find which sensor is bad before you order. If you want a drawing/troubleshooting guide for the sensors, send me your email address. You will find page SF-75 demonstrates the procedure for diagnosis. The sensors are different than the ones you buy at the parts store. Some say you can buy a Denso and be just fine. I just purchased a LexusToyota A/F sensor for $145 on eBay. The sensors are easy to check by using an ohm meter. Good luck! Joe- You are only able to check the heater in the sensors, not the A/F ratio sensor itself. Quote Link to comment Share on other sites More sharing options...
code58 Posted October 5, 2009 Share Posted October 5, 2009 So I'm going to break down and buy three new O2 sensors. The car has one at each exhaust manifold and one downstream of the cats. My scanner is showing all three sensors basically stuck at one voltage (right around 700 mV) rather than bouncing back and forth like I'm used to seeing on my other cars. First of all, the car only has 45k miles on it. Would the factory O2 sensors fail that quickly? Nonetheless, as I'm browsing online I'm seeing sensors by Bosch and Denso ranging from $50 universal types to over $200 for what seem like more vehicle specific. What's the deal? Aren't these all just plain ol' narrow band heated sensors? Why the wide range in pricing? What exactly is needed? CAr is a 2005 RX330. I can't believe that all 3 sensors (2A/F ratio, 1 oxy.) have gone bad and stuck at 1 voltage. Something just not right with that picture. Have you had any work done on the car in recent time (or, yourself done any work on it in recent time) ? When something doesn't look right with a picture. there's generally reason for it. That is completely abnormal for those zsensors to fail in that mileage. I'm not sure whether it's normal for the rear (02) sensor to normally fail in the life of the vehicle even. A/F ratio more like 100k-150k mi. What brought it to your attention to scan it? Was it running poorly. I would think it might not want to run at all with NO action on the part of the A/F ratio sensors. Still say something not right here. IF it needs new sensors, only replace with Denso! And not the universal. I tried them and they didn't work for me. Quote Link to comment Share on other sites More sharing options...
Gruss Posted October 5, 2009 Share Posted October 5, 2009 I don't know about the post-cat sensor but the upstream sensors are Air Fuel Ratio sensors, not "simple" O2 sensors. From my understanding (google) old style O2 sensors can tell if the ratio is "too rich" or "too lean"; hence they switch back and forth as the ECM changes the mixture. With A/F Ratio sensors, they return an analog voltage proportional to the mixture. It provides for much finer control. The ECM therefore does much finer adjustments and you shouldn't see any switching back and forth. For the upstream sensors, there are only two choices Toyota or Denso (Toyota part is made by Denso); the Denso part can be found for a few $$ cheaper ($125 ish on Amazon). Quote Link to comment Share on other sites More sharing options...
joe913 Posted October 5, 2009 Share Posted October 5, 2009 You might want to find which sensor is bad before you order. If you want a drawing/troubleshooting guide for the sensors, send me your email address. You will find page SF-75 demonstrates the procedure for diagnosis. The sensors are different than the ones you buy at the parts store. Some say you can buy a Denso and be just fine. I just purchased a LexusToyota A/F sensor for $145 on eBay. The sensors are easy to check by using an ohm meter. Good luck! Joe- You are only able to check the heater in the sensors, not the A/F ratio sensor itself. code58 - Thanks for sharing. I am at the limit of my knowledge on sensors. I have read you can check the voltage with a scanner in place and the engine running--way too out there for me. Quote Link to comment Share on other sites More sharing options...
joe913 Posted October 5, 2009 Share Posted October 5, 2009 By the way, the Lexus part number for the '99-02 A/F sensors for the RX300 is 89467-48011. Quote Link to comment Share on other sites More sharing options...
ULTM8Z Posted October 5, 2009 Author Share Posted October 5, 2009 By the way, the Lexus part number for the '99-02 A/F sensors for the RX300 is 89467-48011. So the ones in the exhaust manifold are A/F ratio sensors, not O2 sensors. I noticed it when the service engine soon light came on and I scanned the car. I have a 1971 Camaro that I swapped in a 1992-era EFI system, so all of my EFI knowldge comes from that effort. It uses narrow band O2 sensors which bounce back and forth, hovering around a centering voltage (typically around 500mV). This Lexus system seems to operate differently based on what you all are describing? These A/F ratio sensors you guys are talking about appear to be what I know of as wide band sensors? Quote Link to comment Share on other sites More sharing options...
joe913 Posted October 6, 2009 Share Posted October 6, 2009 You are way beyond my knowledge--I ran across this article that may be helpful: http://us.lexusownersclub.com/forums/index...mode=linearplus Quote Link to comment Share on other sites More sharing options...
code58 Posted October 6, 2009 Share Posted October 6, 2009 I don't know about the post-cat sensor but the upstream sensors are Air Fuel Ratio sensors, not "simple" O2 sensors.From my understanding (google) old style O2 sensors can tell if the ratio is "too rich" or "too lean"; hence they switch back and forth as the ECM changes the mixture. With A/F Ratio sensors, they return an analog voltage proportional to the mixture. It provides for much finer control. The ECM therefore does much finer adjustments and you shouldn't see any switching back and forth. For the upstream sensors, there are only two choices Toyota or Denso (Toyota part is made by Denso); the Denso part can be found for a few $$ cheaper ($125 ish on Amazon). Gruss- the A/F ratio sensors are called wide band because they do just that- they swing constantly from one extreme to the other in the course of doing their job. They have a much wider and faster pattern than the 02 sensors. They are able to more fine tune the mixture that way, but if you ever look at a graph of what they do in action, you'll see what I mean. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.