According to a Toyota schematic, this is the upper O2 sensor on the back of the engine (firewall side). Of course it would not be the one in the front that is easy to access.
I found a Denso 234-4209 Universal Oxygen Sensor (Air and Fuel Ratio Sensor) on Amazon for about $35 shipped.
How difficult is it to replace this sensor? Are there other parts that must be removed such as intake manifold or header pipe?
Should I go ahead an replace both of these rear sensors while I am at it?
I have done all sorts of mechanic work but never replaced an O2 sensor. I have had Camrys with over 300k miles, Previa 281K, and this Avalon with 180K but this is the very first O2 sensor to fail me.
I replaced this same one on my Avy a while back. It wasn't necessary to remove anything else to get access, but it wasn't the easiest either. I went at it from below with the front wheels up on ramps. It was difficult squeezing my arm up there. Mine wasn't frozen up like they can sometimes be.
Should you replace both?... I dunno. Some folks say they start getting "lazy"; slow to respond, and should be replaced preemptively. I didn't replace both upstream sensors at the time.
__________________
1992 Camry LE, V6 (3VZ-FE), ABS brakes, 330k miles, dark emerald pearl, owned since new.
1996 Avalon XLS, ABS brakes, moonroof, white, acquired w/ 139k miles, now at 261k.
2001 Yamaha FZ1, Ivan's jet kit, resprung all around, Ohlins in the rear, Race Tech cartridge emulators in the forks, 45k miles.
According to a Toyota schematic, this is the upper O2 sensor on the back of the engine (firewall side). Of course it would not be the one in the front that is easy to access.
I found a Denso 234-4209 Universal Oxygen Sensor (Air and Fuel Ratio Sensor) on Amazon for about $35 shipped.
How difficult is it to replace this sensor? Are there other parts that must be removed such as intake manifold or header pipe?
Should I go ahead an replace both of these rear sensors while I am at it?
I have done all sorts of mechanic work but never replaced an O2 sensor. I have had Camrys with over 300k miles, Previa 281K, and this Avalon with 180K but this is the very first O2 sensor to fail me.
Is your car CA compliant? If yes, you need an A/F sensor which is closer to $100. Make sure you use Denso ONLY. I repalced Bank 1 at about 80k. I now have 110k and Bank 2 is still doing fine. Don't see any reason to replace both. If/when Bank 2 fails, you may not have any driveability issues at all or only minor issues.
Is your car CA compliant? If yes, you need an A/F sensor which is closer to $100. Make sure you use Denso ONLY. I repalced Bank 1 at about 80k. I now have 110k and Bank 2 is still doing fine. Don't see any reason to replace both. If/when Bank 2 fails, you may not have any driveability issues at all or only minor issues.
Thanks for pointing that out. Yes, the sticker on the firewall says it meets California specs. My car has always been in southeast USA so it did not dawn on me that it does indeed have California spec emissions system.
The upstream sensor (before catalytic converter) for California specs is referred to as A/F which is also referred to as a wide-ban O2 sensor. The downstream sensors are all called O2.
Looks like Denso does not make a universal A/F sensor for this engine.
Just ordered the Denso A/F Sensor 234-9007 from StockWiseAuto for $91 including 2-day shipping with coupon code. Amazon was $7 less but estimated delivery was up to 7 days longer. I will burn way more than $7 extra gas driving my 1991 Chevy truck for a few more days.
Looks like there is a steering fluid line really close to the sensor. I suppose removing that line is more trouble than it is worth. I had the intake manifold off back in the summer when I replaced the valve cover gaskets. It would have been MUCH easier to replace this sensor then from the top side. Of course, my luck does not run like that.
Thanks, I appreciate the advice. I had several peopel tell me they did it all from below the car. After about an hour of cutting my arms etc., I came back here. I could nto even reach the connector,much less get a tool to sensor. The steerig rack is too close to the sensor and firewall and frame to access mine from below.
Now to lower the car back down off the stands so I can reach the engine compartment.
Thanks TedL. Removed old sensor from above after removing large hose between air filter and intake. used a regular 7/8" box end wrench 12" long. I had sprayed it several times (both hot and cold) with LPS over the last few days while waiting for the new sensor to arrive. No hammer needed. Cleared the codes with my scanner and running the engine to burn off the antisieze and rust penetrant. Took me about 30 minutes.
I never did find your post though. You have a lot of helpful posts.
My 1993 Previa van with 285k miles has the original O2 sensors, and its mileage has really gone down since I cleaned the EGR valve and intake. I am suspecting that some of the cleaner and carbon gunk may have finally killed the sensors. It has not shown any code or check engine light but it is not running right.
Thanks TedL. Removed old sensor from above after removing large hose between air filter and intake. used a regular 7/8" box end wrench 12" long. I had sprayed it several times (both hot and cold) with LPS over the last few days while waiting for the new sensor to arrive. No hammer needed. Cleared the codes with my scanner and running the engine to burn off the antisieze and rust penetrant. Took me about 30 minutes.
I never did find your post though. You have a lot of helpful posts.
My 1993 Previa van with 285k miles has the original O2 sensors, and its mileage has really gone down since I cleaned the EGR valve and intake. I am suspecting that some of the cleaner and carbon gunk may have finally killed the sensors. It has not shown any code or check engine light but it is not running right.
Use advanced search, keyword [sledge] and my username for "posted by". Date is in April 2011, and I was responding, not original poster.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
ToyotaNation.com is an independent Toyota/Lexus enthusiast website. ToyotaNation.com is not sponsored by or in any way affiliated with Toyota Motor Sales, USA, Inc. The Toyota, Lexus and Scion names and logos are trademarks owned by Toyota Motor Sales, USA, Inc.
1999 Toyota Avalon
Linear Mode
