wura2020:
I am very impressed with your pictorial presentation. It will help a lot of DIY enthusiasts but mechanics will be cursing you for depriving them of an avenue to fleece motorists. Pls how do I get your type of scanner and how much does it cost? Can it scan Lexus GX470?

adeniyisavage:
where did u purchase the sensor and for what price?

adanny01:
Impressive!

You will get from my post on the water-in-ecu episode that i got the dreaded P0420 right after. I have decided to try installing the spark plug defouler inplace of the O2 sensor spacer in attempt to clear the code and eliminate the resultant open loop. I dont know were to get the spacer locally and the defouler is cheap.

My challenge is that my mechanic couldnt get the sensor loose. I will make a second attempt tomorrow but my fear is that the sensor may get damaged in the process of losing.

Piyke:
Remove the 4 10" bolts holding the heat shield in place. I had to do this as the O2 socket that I have is not deep enough to reach the O2 sensor with the heat shield in place.
Heat shield off! (1st pic)
With the heat shield off, use the O2 socket to slacken the O2 sensor (anticlockwise). Haynes manual recommended running the engine for a minute or 2 before doing this(this should be before you disconnect the sensor connector). I did this first thing in the morning without starting the car and was surprised at how easy it was to slacken the sensor.
The 2nd pic shows the catalytic converter with the O2 sensor off.

Piyke:




Has your P0420 come back after you cleared it? I'm guessing that by the time you drive to your mechanic, the whole assembly would be heated up as against turning on the car for a minute or 2 as recommended by Haynes. You may try this.

A simple test to confirm if your cat is actually bad is to hook up ur scanner in datastream mode, start the car and allow to get to operating temp (86deg at least) then hold your RPM at 3000 and observe the bank1sensor2 voltage reading, it should stick around 0.5volts. If it's reading keeps switching between lean n rich the cat may be out.

If it still proves difficult to slacken the O2 sensor, you may need to have a thread chaser handy just in case you damage the cat threads.

adanny01:
Impressive!

You will get from my post on the water-in-ecu episode that i got the dreaded P0420 right after. I have decided to try installing the spark plug defouler inplace of the O2 sensor spacer in attempt to clear the code and eliminate the resultant open loop. I dont know were to get the spacer locally and the defouler is cheap.

My challenge is that my mechanic couldnt get the sensor loose. I will make a second attempt tomorrow but my fear is that the sensor may get damaged in the process of losing.

lonelydora:

Exactly my thought. I changed my sensors with new ones but the CEL came back after some journey to Akwa Ibom. I will try the spacer and defouler method once my mechanic comes back.

adanny01:

Thanks and yes the cel came back after being cleared
4 times. Each time took at least 50miles to come back.

Piyke:




Has your P0420 come back after you cleared it? I'm guessing that by the time you drive to your mechanic, the whole assembly would be heated up as against turning on the car for a minute or 2 as recommended by Haynes. You may try this.

A simple test to confirm if your cat is actually bad is to hook up ur scanner in datastream mode, start the car and allow to get to operating temp (86deg at least) then hold your RPM at 3000 and observe the bank1sensor2 voltage reading, it should stick around 0.5volts. If it's reading keeps switching between lean n rich the cat may be out.

If it still proves difficult to slacken the O2 sensor, you may need to have a thread chaser handy just in case you damage the cat threads.

adanny01:



I successfully unscrewed the O2 sensor this afternoon. However, the spark plug defouler would not fit in it while the threaded section of the defouler is smaller than the hole in the exhaust.

I ran a live scan after that with RPM at 3000 and the B1S2 voltage steadied at around 0.6volts. The range at idle was between 0.1-0.9 volts but sometimes passing 0.9 but not up to 1.0. See the max at the red marker in the screen shot below.

Piyke:


Don't know much about defoulers but I'm guessing there are larger sizes. I think the test reading looks good. What Ericthecarguy said to be bad is rapid switching between lean and rich.
Do you plan to hollow out the cat, before fitting the defouler?

adanny01:


No, i wont.

By my understanding of the youtube videos i watched, its obvious that is not needed. By getting the P0142 does not mean the CAT is out of use but below threshold. The O2 spacer is to take the sensor away from the exhaust flow stream which makes the O2 detect a little more of oxygen and would seem a normal reading after the cat system produces less. Taking out the cat entirely would not help since the spacer will not be able to get some supply of O2. If the spacer fails to clear the code i will consider buying a used one.

However, its a challenge to buy a used one since even as expensive as it is being sold, you will have to drive atleast 100miles to know if your purchase is good enough not to produce the P0142. By that time my brothers in the mechanic wont take it back unless that dealer is too good.

For now, i will look to order the spacer from Amazon.

Piyke:
I have now driven more than 150miles since replacing this downstream O2 sensor, no CEL. I would keep driving and see if it's now gone for good.

Piyke:


Eventually you may need to gut out the cat, my bro had this same problem on his 03 Camry, from the time the P0420 appeared on his vehicle it took 2years plus for the car to come to the point where the car barely moved despite throttling. He finally gutted it and replaced with aftermarket cat and the CEL has been off for about a year now.

adanny01:


Yes i guess eventually i must. Instead of that i will fit a test pipe with an O2 space fabricated on it as i have read. The hollow section of empty CAT may not be a good thing for the engine and a straight pipe is recommended instead. For now, i want to try the spacer and if it fails, then the straight pipe thingy.

For now, most mechanics i have asked have no idea that a spacer of that dimension exist. Thats because most spark plugs threads are same but the nut are either 19 or 21mm while the O2 sensor has a bigger threading with 22mm. With the new $ exchange rates, the spacer is too expensive to make an orders. I think i can fabricate the spacer by welding a 22mm nut to a fitting pipe and having the other pipe threaded to correspond to the CAT O2 hole. It shouldn't cost more than 1k for labour and parts.

Emperoh:


Hmmmm, very instructive. I am coming up with my own 02 sensor and cat below threshold wahala.
Few mins, lemme scan the car.

adanny01:


Its going to be 24hrs soon. Waiting!