Oxygen Sensor Replacement - Help

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I grabbed a tool like this, it allows you to remove the unit without cutting the wires, helpful when installing.

 

Most cheapie auto parts O2 sensor sockets will work. A line wrench of that size also would be fine. It is possible that you could get it off with an open end wrench or, worst case, a crescent wrench.

You'll have to unhook the wiring harness from inside the car. I can't remember if it is under the passenger seat or the console.

 

Remove passenger door sill and kick panel, pull carpet back enough to see the O2 wire entering the car to the right of "the hump". There is a disconnect inside the car. If you unhook the wire and push it down below the floor you can get a box wrench over the wire to remove the sensor...or go buy a $10 O2 sensor socket at your FLAPS. Spray penetrating oil on the sensor threads first if you live in salt country.

 

thank you.. i've been looking at a diagram on alldata for a while couldnt' figure it out. geesh i'm slow
hopefully this solves my p0420

 

If your car has logged DTC P0420, the most likely failed component is the catalytic converter.

If you want to replace a sensor first in hopes that will make the engine ECU think the catalytic converter is OK, then you would want to replace the air fuel ratio sensor which is upstream from the catalytic converter. Service access to the A/F ratio sensor requires removal of the inverter.

 

Yeah i'm sure it is the cat, but just high hopes as i've seen others have intermittant success with replacing the sensors. More than likely i will just ignore the code for now and save up for toyota parts as a few people have told me that non geniune parts (on several different car manufacturers) will have efficency less than 90 and that will throw the code again.

 

Just a follow up. I did replace the converter but my mpg is still abysmal at 39-40
It did clear the p0420 though

 

1. When were the iridium spark plugs last changed?
2. If the plugs are in good condition you may consider changing the air/fuel ratio sensor upstream from the catalytic converter.
3. What is your driving pattern that results in 39-40 mpg? How long is a typical trip in miles and minutes, what is the average speed, is this on flat or mountainous terrain, etc.

 

Spark plugs were changed at 175k.

The air fuel sensor would be my next step. However I'm trading in the car soon. I just thought I'd let everyone know a new cat cleared the code. Oh by the way I did use an aftermarket cat. Eastern catalytic from amazon. 240 + 100 to install

 

I was looking at the threads below your post, but didn't see any that said you completed your repair. I have the same code P0138 on my '04 Prius. Did replacing the post cat O2 sensor fix your problem? It looks like 3prongpaul provided good info on how to get to the plug if changing the sensor is the right answer to P0138. Rmsmith looks like he had more serious problems.

 

Does anyone have a good write up on the best way to replace the upstream o2 sensor on gen2? The one located on the manifold, I did the job once before but it took me 2 hours and I'm sure theres a better way but I didn't have time to research.

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