CEL Code 420 and Replacement Catalytic Converter / Exhaust System help

[Erich_870]

I have a 1999 3.4L 4unner with a reoccurring CEL, code 420. It's been on for 2 years now and I've replaced both O2 sensors and the CEL comes back every time I clear it. The rig is Cali emissions too, with dual catalytic converters.

Thanks to Bruce sharing a new source for reasonably priced replacement cats ( http://stores.ebay.com/Muffler-Express-Distribution ), I’m planning to fix this problem once and for all this spring.

What I’m needing help with is verifying which cat needs to be replaced.

I’ll also be looking at whether the rest of my exhaust system needs replacement too. I’ll post some pics of the current system in the day light tomorrow.

My gas mileage has gone down from 18-19 avg to 14-15 over the same time period so I'm hoping to fix that by replacing the faulty cat and whatever else could be to blame.

Thanks,

Erich

[corax]

it will be one of the cats between the oxygen sensor, NOT the one after the last O2 sensor (no way to monitor that one = can't set a code).

[Erich_870]

it will be one of the cats between the oxygen sensor, NOT the one after the last O2 sensor (no way to monitor that one = can't set a code).

Right, the second cat has no O2 sensor monitoring it...

How can I check if the second cat needs to be replaced too? I'm worried my bad gas mileage is from a clogged cat or something wrong with he muffler.

Erich

[Seanz0rz]

i dont have a twin cat vehicle (thank god)

can you switch the "bad" one to the rear, and the rear to the front?

[corax]

How can I check if the second cat needs to be replaced too? I'm worried my bad gas mileage is from a clogged cat or something wrong with he muffler.

Erich

Take it off and shine a flashlight through it onto a piece of paper - don't bother trying to look through the sub-strait as you'd have to get the angle just right to see through it

[Erich_870]

i dont have a twin cat vehicle (thank god)

can you switch the "bad" one to the rear, and the rear to the front?

They are two different and dissimilar pieces.

Here's the front one (the one that's throwing the code) http://cgi.ebay.com/ebaymotors/ws/eB...m=200340513174

And here's the back one http://cgi.ebay.com/ebaymotors/ws/eB...m=200379790154

Erich

[BruceTS]

I just went ahead and got both cats, since I didn't want to have any issues....since the price was right.

[Erich_870]

I just went ahead and got both cats, since I didn't want to have any issues....since the price was right.

That's kind of what I was thinking. My luck the hardware on the back cat would be to far gone and I'd need a new one any way and then be stuck until it arrived, lol.

I need to get a pic of the cat back exhaust tomorrow to see if you guys think I need to do the whole thing at once.

Erich

[Crinale]

since your truck is 11 years old now... it probably wouldnt hurt...

i will probably redo my whole exhaust at some point, but i have more pressing issues right now, so ill just wait til i break it off :-P

[YotaFun]

Well
Erich,
looks like I will be joining you in the venture, just not for my 4Runner.
My GTI just threw a P0422 and upon research tells me that it too is time for me to get a new cat (granted the car does have 222k+ so I am sure it is due.)

I will be getting the cat for my aunts mini van soon and installing that in a few weeks, if all goes well and her code goes away I will be ordering one for the GTI