Question about P0421

[Frozen]

Alright, so I had that CEL problem for awhile. I replaced almost everything except the precat. I replaced both O2 sensors which didn't do the job. The post cat which didn't do the job. Then I replaced the spark plugs which did the job for three months and now the light just came back on with the same exact code. Does this mean it's the precat for sure that's gone bad?

Also, if I just ignore the CEL and leave it. Will it damage my car having a bad precat? Like I won't have anything to worry about besides an emissions test?

 

[Tzar177]

you might get bad gas mileage with the cel on. if you didnt wanna pony up for another precat, you can always install CEL eliminator trick on the 2nd o2 sensor using 2 spark plug nonfoulers

 

[Frozen]

How much mpg do you think I'll be getting? And is that the only problem it'll be causing?

 

[KrayzieFox]

I have a spare pre-cat if you need one..

 

[Frozen]

Actually, I'm kinda confused here. I'm pretty sure the problem is my spark plugs since you know, changing the spark plugs fixed the problem in the first place. Maybe they just got fouled up quickly somehow? Does anyone know why they'd get messed up so quickly though?

Should I just change my plug wires and distributor cap and rotor and spark plugs to see if that does the trick again?

 

[TheMAN]

dude
you wasted all your time and money for what? if it says P0421, it is 99% true that your cat is bad! I have rarely seen anything else that causes this code

and WHAT distributor cap?

 

[StealthWyvern]

dude
you wasted all your time and money for what? if it says P0421, it is 99% true that your cat is bad! I have rarely seen anything else that causes this code

and WHAT distributor cap?

The one he got charged for that the car doesnt have. (silly)

 

[jonridinhi]

If the cap gose bad the the flux capacitor stops working and i guess that could throw that code them.(alright)

 

[Frozen]

My bad, I know nothing about cars. I was just doing research online and I read somewhere that changing it could help? But I guess that doesn't apply to my car if it doesn't have one?

 

[KrayzieFox]

Our cars have coils instead of a distributor cap.. but if your coils were bad your car would run like s*** and throw other codes.

 

[Protege_MP3_506]

I had the same problem too. My first cat is bad cause of my coils when they went bad. I guess it sends alot of the unburnt fuel through and it clogs it. I did the MIL eliminator thing and it was a piece of cake to do and my CEL hasnt turned back on and that was probably about 800 miles ago

 

[CulRidr]

^except you never ACTUALLY fixed the problem, you only got rid of the CEL. Your cat is probably still bad...

 

[siikduke]

In my opinion if you want to get rid of that pre-cat, gut out the pre-cat and add the non-fouler or do what I did and just get the OBX 2.0 NA Header and use the non-fouler. Dealership wanted $1300 to fix the cat, I just went with the OBX Header from Protege Garage.

I had the same error code and when I was installing the new header, the old pre-cat was blown in and falling apart~!

 

[Protege_MP3_506]

^except you never ACTUALLY fixed the problem, you only got rid of the CEL. Your cat is probably still bad...

True. But I passed emissions

 

[R-X-R]

if ur pre cat is damaged and if u leave it like that it can also damage the post cat in the long run. only if u r really concerned about polluting.,.,.