P0420 Solution - Toyota Nation Forum : Toyota Car and Truck Forums

amisso41 · 06-23-2010, 08:01 AM

I have a 2000 corolla LE with 180,000 miles. I had the CAT replaced with an aftermarket Magnaflow (welded in) that the shop welded in about 15,000 miles ago and CEL came on after about 5,000 miles with P0420. Took it back to the shop said the cat was fine and they also verified both O2 sensors were working correctly. I had no noticeable problems with the car and MPG and operation was still normal. Needed to get it inspected (MA) and was told the only option for it to pass was to pay $1500 at the dealer for an official toyota CAT.

I found this fix on a a different forum involving a spark plug defouler, drilling it out, and attaching it the rear O2 sensor. Rented an O2 sensor wrench from autozone and was even able to get the rear sensor off without lifting up the car at all (with a hammer and lots of PV Blaster). Link to photo instructional and part below.

http://www.k-series.com/forum/showth...hanical-02-Sim

Amazon

http://www.autozone.com/autozone/cat...&brandName=OEM

2,000 miles later I have my inspection sticker, no CEL, and no drop in MPG or performance. Hope this helps.

joe68 · 08-31-2011, 06:01 PM

What spark plug non-fouler did you use? brand? model? size?

amisso41 · 08-31-2011, 09:03 PM

I used a Dorman model # 42009

Amazon

Quick2000 · 09-01-2011, 10:49 AM

That's how I fixed mine as well. Works flawlessly.

kitzmiller88 · 09-04-2011, 04:20 PM

doesent this trick cause the ecu to run leaner? ive heard you have to use a octane booster to even it out? is this true

Quick2000 · 09-04-2011, 05:25 PM

Nope, the post cat o2 sensor is for emissions and detects if the catalytic converter is functioning properly. The upstream o2 sensor is the one the ecm uses to adjust air/fuel ratios.

mital917 · 09-08-2011, 11:52 AM

[QUOTE=amisso41;3238352]I have a 2000 corolla LE with 180,000 miles. I had the CAT replaced with an aftermarket Magnaflow (welded in) that the shop welded in about 15,000 miles ago and CEL came on after about 5,000 miles with P0420. Took it back to the shop said the cat was fine and they also verified both O2 sensors were working correctly. I had no noticeable problems with the car and MPG and operation was still normal. Needed to get it inspected (MA) and was told the only option for it to pass was to pay $1500 at the dealer for an official toyota CAT.

I found this fix on a a different forum involving a spark plug defouler, drilling it out, and attaching it the rear O2 sensor. Rented an O2 sensor wrench from autozone and was even able to get the rear sensor off without lifting up the car at all (with a hammer and lots of PV Blaster). Link to photo instructional and part below.

http://www.k-series.com/forum/showth...hanical-02-Sim

http://www.amazon.com/Dorman-HELP-42009-Spark-Non-Fouler/dp/B000CO91FY/ref=sr_1_1?ie=UTF8&s=automotive&qid=1277297074&sr=8-1

http://www.autozone.com/autozone/cat...&brandName=OEM

2,000 miles later I have my inspection sticker, no CEL, and no drop in MPG or performance. Hope this helps

what size drill bit did you use?

105 · 09-09-2011, 07:48 PM

Did you drill it all the way through with a half inch bit or just enough so the 02 would fit?

Your instruction link isn't working for me.

105 · 09-16-2011, 11:24 AM

Well so far I've had no trouble (100 miles). I drilled the non-fouler completely out with a 1/2" drill bit but not all the way through. Just enough to where it started to stretch the hole open at the end of the non-fouler. This way it will let very little fumes reach the 02.

I used vice grips and my foot to hold the non-fouler in place on the floor while I drilled it little by little.

I did this because my cat was starting to fail so I replaced it with a straight pipe.

mital917 · 09-18-2011, 12:22 PM

Quote:

Originally Posted by 105

Well so far I've had no trouble (100 miles). I drilled the non-fouler completely out with a 1/2" drill bit but not all the way through. Just enough to where it started to stretch the hole open at the end of the non-fouler. This way it will let very little fumes reach the 02.

I used vice grips and my foot to hold the non-fouler in place on the floor while I drilled it little by little.

I did this because my cat was starting to fail so I replaced it with a straight pipe.

i drill out the non fouler with a 1/2in bit and i have a high flow flowmaster cat and i still have the cel on any suggestions?

Quick2000 · 09-18-2011, 01:55 PM

Did you reset the ecm? And did you drill all the way through the defouler? or just enough so the O2 sensor could fit in?

mital917 · 09-18-2011, 02:03 PM

i did reset the ecm n i drilled all the way through the fouler

Quick2000 · 09-18-2011, 02:50 PM

That's why- you're not supposed to drill all the way through. You're supposed to leave the hole at the end of the defouler small.

105 · 09-19-2011, 07:33 AM

Quote:

Originally Posted by mital917

i did reset the ecm n i drilled all the way through the fouler

Since you did drill it all the way through, just screw the other nonfouler that came in the pack onto the end of the drilled one. I've seen it done this way too.

militarydave · 10-04-2011, 09:34 PM

my 1999 CE has 177xxx miles on it. the P0420 code came on earlier today. I re-set (cleared) the code with an OBDII code scanner (a good one, not the el cheapo autozone kind).

so far so good. code hasn't come back. If I dont do this fouler/drilling thing, would I have any adverse effects on the car, besides the state inspection?

thoughts?