Oxygen Sensors

[keyskindagirl]

I found out today that I need to replace the 02 sensors in my 1999 RX300. I've located them online at a fiarly reasonable rate (the mechanic wants $300 each). Is installation something that can be done by someone that does their own basic repairs?

[ColinBarber]

Make sure you get the correct ones. The RX uses air/fuel ratio sensors rather than standard oxygen sensors.

[Lexusfreak]

I found out today that I need to replace the 02 sensors in my 1999 RX300. I've located them online at a fiarly reasonable rate (the mechanic wants $300 each). Is installation something that can be done by someone that does their own basic repairs?

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$300 for each o2 sensors, OMG! How many are there to replace? :o

[RX in NC]

Replacing oxygen sensors can be handled by an experienced do-it-yourselfer but it helps to have the proper tools since you can wind up damaging your exhaust manifold if you don't do it slowly and carefully. You may need to get the appropriate oxygen sensor wrench because a regular wrench tends to break or crack the manifold if it's handled too roughly. You must be very careful when initially breaking the seal which the sensor base has formed where it screws into the manifold. Don't get in a hurry and be sure to allow yourself plenty of time for the job. It would be a good idea to get a mechanically-inclined friend to help you or actually do the job for you if you decide to order the sensors and go for it.

[lsrxlex]

I also have a 1999 RX300, with 85k, (no warning lights on dashboard yet), and I'd like to know when do I have to change my O2 sensors too.

Thanks.

[RX in NC]

When a "check engine" light illuminates on your dashboard, go to the nearest AutoZone and they'll read the associated trouble code at no charge. If the trouble code indicates that one of your oxygen sensors is failing, it will point to the correct one and that's when you should obtain the correct replacement sensor and change it. These are relatively expensive components and you're usually better off not trying to change them as a preventive maintenance action. Wait for the dashboard light and associated trouble code.

If the trouble code points to your mass air flow sensor, you should try cleaning this sensor before you decide to replace it. It's the easiest to find and remove yourself and is often the first sensor to begin to fail. It's also much less costly than the other oxygen sensors. There are several archived threads (and photos) on this forum that will instruct you on how to find and clean the mass air flow sensor. Do a search on "mass air flow sensor" or "MAF" and you'll learn quite a bit about this particular problem.

If you have 85,000 miles on your vehicle now and you've never had a sensor failure, you're doing very well indeed. Many of these sensors fail between 60,000 and 80,000 miles. The original mass air flow sensor on my wife's 2000 RX300 failed at less than 50,000 miles.

[dgorrie]

Regarding pricing, I bought the rear engine sensor (Bank 1?) a couple months ago from http://newlexusparts.com for $188, with free shipping. Add tax if you ship to Texas. I think the P/N is 8946748011, but verify that. My problem is intermittent, so I actually haven't installed it yet.

The rear sensor is under the driver's seat, and I believe that P/N is 8946549075 (from Alldata site). Newlexusparts price is about $115. You have to remove the driver's seat to remove the connector, but not a big deal. The rear sensor itself is under the car.

About a year ago, I bought the air mass sensor from the same folks for $115.

Regarding O2 sensor sockets, I know there are long versions and short versions. I found a short one at O'Reilly's for $10. Might be handy in tight areas.

In looking over these sensors, I figure the one at the front of the car (Bank 2?) is pretty easy, and the one under the driver's seat. The one at the rear of the engine area will be trickier, but very feasible given the cautions already quoted.

[keyskindagirl]

The mechanic I took the car to said he could reset the check engine light and then we should wait to see if it comes on again. Two days later it came back on. Later that same day I had to put a tank of gas in the car, and on the way home, the light turned itself off!

I am thinking it might have been a gas cap thing. Has anyone else had this smae problem? Also, since the light is out now, I think I should leave the O2 sensors alone, since it seems like there is a pretty high risk in taking them off, such as causing more new problems. Any thoughts?

[keyskindagirl]

I also took the car to Discount Auto (the only national chain we have in this area) and they said they could only read domestic cars, (Ford Chevy, etc.) no imports like Toyota or Lexus.