help! p0420!

agon3279

Original poster
Member
Jan 1, 2013
41
Hello there everyone. Im new here. Somebody directed me to this site instead of the other well know forum.
Well, i recently got the infamous po420. I used some seafoam on the intake just as routine maintinence .Well i think that the seafoam may have caused the problem. Now my truck seems sluggish and it takes a long time for it to wind up. I used the scotty kilmer trick and poured some pure laquer thinner in the tank to see if it changes anything. But so far i cant .notice a difference. Any suggestions would be greatly appreciated.
 

Short Bus

Member
Dec 2, 2011
1,906
Your Rainier wants to smoke some chronic yo :crazy: LOL
 

jrSS

Member
Dec 4, 2011
3,950
1St of all what does the temp read on your dash? And if it doesnt read 210...u have a bad thermostat and that can cause your sluggish issue due from clogged cats.
 

agon3279

Original poster
Member
Jan 1, 2013
41
The temp gauge never moves from 210 once warmed up. I already replaced the coolant senso about two months ago
 

agon3279

Original poster
Member
Jan 1, 2013
41
I went to the local o'rileys. They put it on the scanner, and cleared the code. so far so good. And ever since they reset it, it seems like it has no more hesitation. but i don't have my hopes up just yet. I only have driven it two drive cycles. still 3 more to go
 

agon3279

Original poster
Member
Jan 1, 2013
41
CaptainXL said:
Why did you change it? Did you have a P0128 code?
Yes i did. I've only had the truck for three months now. I bought it from carmax. It was still under warranty when it happened. Plus a few other things that were wrong with it they fixed to under the warranty. But i'm well past the thirty day warranty and at this point i'm really hoping that the cat is not bad. I know that all the trucks are kind of picky when it comes to aftermarket components.
 

CaptainXL

Member
Dec 4, 2011
2,445
agon3279 said:
Yes i did. I've only had the truck for three months now. I bought it from carmax. It was still under warranty when it happened. Plus a few other things that were wrong with it they fixed to under the warranty. But i'm well past the thirty day warranty and at this point i'm really hoping that the cat is not bad. I know that all the trucks are kind of picky when it comes to aftermarket components.

Probably too late now. Looks like they replaced the wrong part. Should have changed the thermostat instead of the coolant temp sensor. Get the thermostat changed and hope for the best. If the cat isnt clogged you can try at least to throw some cataclean in your tank and see if that solves the inefficiency issue.

And dont be afraid to get the rpms up on the highway to try and force some of the crud out. 3rd gear at 70 mph should put you at about 3k rpm. Keep it at 3k for about 10 minutes onthe highway. Just keep an eye on the temp.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
P0420 comes from "low cat efficiency". The PRE-cat O2 sensor wiggles from low to high voltage around once per second or sometimes 2 times a second as the PCM adjusts the fuel-air ratio

The POST-cat O2 sensor is much steadier, since the cat is supposed to burn any excess fuel and cause the output exhaust stream to be predictable and non-polluting.

A good scan tool that can look at the PRE and POST cat O2 sensor readings can tell in an instant if the cat has "low efficiency" for being broken or missing. I had an intermittent P0420 and troubleshot it this way. My POST-cat sensor readings wiggled up and down at the SAME rate as the PRE-cat sensor. That wasn't right, and will trigger the P0420 code.

Looking closer at the cat canister and I found a dent put there by an offroad rock. The ceramic cat element inside had broken up and bounced around until it was all broken and 1/3 of it had departed the canister.

A cat that has "low efficiency" for being clogged will show itself by high backpressure as measured in the PRE-cat O2 sensor hole.
 

agon3279

Original poster
Member
Jan 1, 2013
41
ok. so after six drive cycles the CEL came back on. Going to get it scanned tomorrow. But, just one question. If I do get an aftermarket cat, will it be ok? Or will I have to get an oem fit?
 

Ghost

Member
Jun 1, 2012
932
Short Bus said:
Your Rainier wants to smoke some chronic yo :crazy: LOL

Lol ! Gr8 minds think alike
 

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