Fixing Bad Catalytic Converters With P0420

Status
Not open for further replies.
Joined
Jul 22, 2005
Messages
11,943
Location
NorthEast
Quote:
While the Magnaflow fit very well and appeared well made, it didn't last long, only about 65K miles before it repeatedly set off the P0420 code.
I have to be honest with you but 65K is a long time even for some of the OEM converters! Thanks for posting this information. Did you try Scotty's paint thinner method? I don't remember if the paint thinner method is supposed to be stronger than the laundry detergent per his video.
 
Joined
Sep 18, 2012
Messages
6,092
Location
DFW
My GF has an 03 Highlander with the side-by-side cat setup (can you say expensive?). She gets that code about 2-3 times a year. Toyota has a TSB related to it and it is just due to the fact that the factory setting for the ECM on the O2 sensor readings is too "tight." I have checked the actual sensor voltages - on all four sensors - and they are working fine. I have also measured cat temps with my IR thermometer - also fine. So, I erase the code and she motors on for another 4-6 months. Yet another example of how the CEL can sometimes be a dirty trick. Nothing wrong with the car or its level of emissions. Just programming without enough tolerance built in. Toyota will reprogram the ECM per the TSB, however, they won't do it for free.
 
Joined
Jan 15, 2008
Messages
20
Location
minnesota
I had seen the video of Scotty running a gallon of paint thinner in the tank but I didn't try it. Instead, I ran two cans of Berryman B-12 on a 1/4 tank of gas but it didn't do enough to shut off the check engine light.
 
Joined
Jul 11, 2010
Messages
534
Location
Hampton, VA
Originally Posted By: L_Sludger
A good fix for P0420 is a couple of spark plug anti-foulers screwed into the post-cat O2 sensor bung, with the O2 sensor screwed in at the end.
Didn't work for me. I even tried 2! I'm going to try the acetone route probably because my safari has 230k miles and runs like [censored]. The calalytic converter is welded and I don't feel like messing with it. VA doesn't require tests in my area. As long as the light isn't on...wink wink
 
Joined
Sep 2, 2005
Messages
9,067
Location
MIchigan
Originally Posted By: biron
I had seen the video of Scotty running a gallon of paint thinner in the tank but I didn't try it. Instead, I ran two cans of Berryman B-12 on a 1/4 tank of gas but it didn't do enough to shut off the check engine light.
It's actually Laquer Thinner. And it's 9 gallons of gas per 1 gallon of Laquer thinner. And you need to run it at highway speed for about 150 miles. If that doesn't work remove the Cat and soak in laudry detergent overnight. No guarentees. Scotty Kilmer.
 

01rangerxl

Site Donor 2021
Joined
Apr 8, 2006
Messages
10,875
Location
Birmingham, AL
My truck had a fairly major cat failure, but never set a catalyst efficiency code. In fact, it never set a code at all. It was acting like it couldn't breathe. Performance was fine below 2500 RPM, then it would kind of fall on its face, then above 3000 RPM it would flash the CEL indicating a misfire, but would not set a code. I could hear major detonation/misfiring going on at these engine speeds. Went over the ignition system and fuel system and nothing was going on there...had to be airflow related. One day on the highway it started misfiring, I reached over and touched the floorboard...it was HOT. Like really freaking hot. The truck had four converters (LEV, default CA emissions)...I pulled the rear two and ran a serp belt tool through them. I tried to get the two up front, but that was a no-go due to the bends in the pipe. I ended up ordering a Magnaflow y-pipe. Unfortunately the Magnaflow stainless y-pipe looked good, but did not fit the truck at all. Simply impossible to install it on a automatic trans truck. I swapped it for a Walker, and the Walker dropped right in like a glove. 7 months later, no catalyst efficiency code. No CEL at all in fact. Apparently the two Walker pre-cats are doing the job. No misfires, no detonation, no catalyst efficiency code...just a smooth running, slightly louder truck. I fully expected a P0420, but it has not happened. Not really proud of my "fix" for the rear converters, and may eventually put new ones on as the truck does drone and attracts unwanted attention, but I was quick fixing and when all performance problems went away and there was no CEL, I kind of stopped. I am myself shocked that the CEL has not gone off at all with two rear cats completely gutted. The front two seem to be doing a good job of cleaning, or this old Vulcan just doesn't pass too many nasties through the exhaust somehow. Go figure. BTW - Tried Mr. Gasket Cataclean and it did nothing.
 
Last edited:
Joined
Oct 4, 2007
Messages
1,606
Location
Oahu, Hawaii
Originally Posted By: DBMaster
My GF has an 03 Highlander with the side-by-side cat setup (can you say expensive?). She gets that code about 2-3 times a year. Toyota has a TSB related to it and it is just due to the fact that the factory setting for the ECM on the O2 sensor readings is too "tight." I have checked the actual sensor voltages - on all four sensors - and they are working fine. I have also measured cat temps with my IR thermometer - also fine. So, I erase the code and she motors on for another 4-6 months.
I had Lucas fuel treatment throw a P0420 in my Toyota truck several times. Ran a full tank without that stuff, cleared the CEL and no more P0420. Even quality of gas or what you put in can throw a code.
 
Joined
Sep 18, 2012
Messages
6,092
Location
DFW
I tend to agree. I mention to her to stick with one of the stations in our area that sells top tier gas. She mostly buys Murphy from Wally World.
 
Status
Not open for further replies.
Top