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Old 04-26-2018, 11:50 AM   #19
ThinkPad
 
Drives: Yaris XP9 1.3 '06
Join Date: May 2016
Location: -
Posts: 33
Bit of a late reply. I ordered a set of 'defoulers' (link).

I can't get the O2 sensor off, it seems very stuck. Strange thing is that the sensor before the cat was easy to get loose (just for trying, nothing else as the defouler needs to be placed on the second sensor). So i'm sure the direction (lefty loose) is correct. I unclipped the connector, put the wire through the ring spanner, put the ring spanner on the nut. Tried hammering on the end of the spanner, but no movement :(

Also i'm not sure if i have enough free space between the sensor and other parts (transmission, manual in my case) for the defouler(s) to fit. Seems quite tight space.

Does anyone have pictures of the defouler(s) fitted on his/her Yaris?

Last edited by ThinkPad; 04-26-2018 at 12:00 PM.
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Old 01-06-2019, 10:42 AM   #20
ThinkPad
 
Drives: Yaris XP9 1.3 '06
Join Date: May 2016
Location: -
Posts: 33
We still have a P0420 error message on our Yaris 2006 sometimes. It only appears when you drive at a constant speed of around 80-100kph it seems.

Have tried before to place a 'defouler' but i couldn't get the second lambda sensor loosened. But it also won't fit i guess, as the sensor is mounted at a weird angle which doesn't give much room for the defouler.

Have recently let Torque log via OBD during a 20 minute highway ride. I filtered the output in Excel at engine rpm> = 3000 so that I only have the highway piece.

Both sensors (upstream & downstream) in one graph:

(Click for big picture)

Both sensors separately:

(Click for big picture)

When I look at the combined graph, I think: hmmm the 2nd sensors fluctuates a lot. But if I look at the graph of downstream separately, then I think: it is not too bad, value is fairly constant.

Is there someone who can say something about the condition of the catalytic converter?

Last edited by ThinkPad; 01-06-2019 at 11:48 AM.
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Old 02-01-2019, 06:01 AM   #21
ThinkPad
 
Drives: Yaris XP9 1.3 '06
Join Date: May 2016
Location: -
Posts: 33
Nobody?
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Old 09-21-2020, 05:12 AM   #22
ThinkPad
 
Drives: Yaris XP9 1.3 '06
Join Date: May 2016
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Posts: 33
After driving for some years with this error and clearing the Check Engine Light (CEL) regularly, I ended up replacing the secondary O2-sensor (the one behind the catalytic converter).
I used a Denso DOX-0109 sensor for which i paid around €48/$55. This version you re-use the connector from the old sensor. A ready to install sensor was about double the price of this Denso.

Placing the new sensor was easy, but removing the old one was a real pain. It was very, very stuck because of rust (due to salt used on the roads in winter here). I removed the exhaust from under the car, otherwise i could not put enough force on the sensor to remove it, even when using lots of penetrating oil. In the removal process the thread got stripped, but luckily a friend of mine had a thread cutter for M18x1,5. After that was done, the placement of the new sensor was easy. Copper grease was supplied with the new sensor to prevent it getting stuck again.

I have driven around 700km/434mi since, and the CEL hasn't turned on anymore, whereas normally it would light up within 50km/30mi after clearing the CEL.

When looking at Torque, i can see that the sensors now show normal behaviour. The first sensor shows a waveform, the second one shows roughly a flat horizontal line around 0.5 - 0.6V when drving at a constant speed. Before, the second sensor was mimicking the first one. I would really have thought the catalytic converter was shot, but so far it just seemed to be a faulty sensor. The car mileage is 154k km/95k miles.

By the way, i ended up not using the 'spark plug defouler', as the angle of the sensor is quite bad, with the defouler in between the sensor would not fit between the exhaust pipe and gearbox.
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Old 09-21-2020, 03:52 PM   #23
komichal
 
Drives: Yaris 2007 1.3 2SZFE 64kW
Join Date: May 2012
Location: CZ
Posts: 222
Same error here - P0420, always came back after a few days after cleaning.
I also decided to change the post-cat O2 sensor before doing anything with the cat. I used the Denso direct fit - costs more but saves time with soldering etc.

As ThinkPad mentions - removing the sensor is not that easy but at the same time it went better than I expected considering all the salty roads here during winter. I just poured some WD40 on it the day before. On the day D when I arrived home I jacked the front part of the car up a bit, sprayed it again with WD40, I used the O2 sensor hexa-socket, put it on the ratchet, put 1m pipe on the ratchet and PULLED. It was tough even on the 1m pipe but it suddenly CLICKED and I was able to unscrew it with ratchet only.

I also changed the upper O2 sensor, again with the particular Denso direct fit type. If the bottom O2 sensor was tired then the upper one must have been on its way too. The upper one was easy to unscrew - no need to use the pipe, just the ratchet with the socket and it went nicely.

This was half a year ago. No P0420 since then.
Fair to say - I have not noticed anything with the new pre-cat O2 sensor - no better engine run, no consumption improved. But actually I do not care that much. That P0420 is gone.
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Old 12-28-2021, 11:35 AM   #24
komichal
 
Drives: Yaris 2007 1.3 2SZFE 64kW
Join Date: May 2012
Location: CZ
Posts: 222
Tadah! A year and a bit passed away and my P0420 is back.
Will try OXICAT first to see if it helps. I do not think it makes sense to replace the downstream O2 sensor again... may end up with a new cat... or maybe just the defoulers...
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