code p0421

[hershman]

hello every one...I have a 99 galant 2.4l.. yesterday the check engine light came on.. I read the code and it, read, upper bank TEMP is below threshold in the catalyst. Darn it i cant remember word for word but its close..
And I remember this happening a few yrs ago. we had to sign up for the CAP CA assistants plan. It turned out to be the speed censer one the crankshaft..has this ever happened to any one else and what can I do to prevent it... Thank You everyone

[oakrdrs187]

"Bank 1 catalyst below threshold"

Round here we hate that code, yet know it by heart.

Usually catalytic converter is bad.


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[silverbullet02]

http://www.club3g.com/forum/performa...t-5-bucks.html

Check this out. I had the same issue and thought it was the cat. Worked like a charm for me. And if it doesn't work, it's only a few bucks wasted.

[2002BlackDragon]

This is exactly what I did to the black G. I had the DC Headers and I NEVER threw a code. Worked like a charm and super easy to do.

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[oakrdrs187]

http://www.club3g.com/forum/performa...t-5-bucks.html

Check this out. I had the same issue and thought it was the cat. Worked like a charm for me. And if it doesn't work, it's only a few bucks wasted.

If you have to do that it is the cat, it has lost its efficiency thus the CEL, the fouler trick only fools the ecu into thinking the exhaust flow is carrying less carbon monoxide resembling a working catalytic converter. So yea the trick gets rid of the light but doesn't fix the problem the light is being triggered for.

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[2002BlackDragon]

Well my DC header deleted my cat so that's why I needed it. But the trick works.

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[oakrdrs187]

Not saying it won't work for the light. Im just saying that for a stock exhaust car the code usually points to a bad pre-cat.

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[2002BlackDragon]

Yeah. I was just saying that for me it worked keeping the light off. I know some had done the same thing and still got a light on.

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[Silvertune]

The point is if you have a bad cat, replace the cat. 95% of them time when they go bad they get plugged and which point the CEL is the least of your worries. Don't be a moron, fix your shit.

[2002BlackDragon]

Lol... deff right there. Gotta fix that cat. To be honest, I started at the link. I didn't read the rest of the thread. So I thought the link started this thread and was just talking about fixing the light situation.

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[hershman]

Hey Raider.. Thanks as always for getting back to me with advice, I will definety look in to doing that. This is the first time a cpl yrs i've had the light come on. if it dose it agine I trying that out.. Thanks again my friend...hershman

[hershman]

Hello Silvertune..
I agree fix your shit is the way to go, but I've had this code before, I couldnt afford the repair cost and had to sign up for the CAP CA assistants plan. Well after extensive diagnostics, as per CA law It turned out to be the input speed censer one the crankshaft..

[damCapn]

I am having this code thrown with my 03 galant, would removing the cat all together and going straight pipe be a way to go? Or will I have to reprogram my computer? I live in a no smog check city so thats not an issue... Or maybe would "gutting" the cat fix the problem?
Thank you in advance.