Check Engine Light Was On...Now Off...I've Got the Code...
 

My check engine light came on last fall and stayed on for about two weeks. I got the dealer to check it and they told me it was a bad catalytic converter, but they cleared the code and it did not come back until recently. I didn't believe the dealer for one second, and still don't.

The CEL came on again about a week ago, but then went out on it's own about five or six days later. I got a guy here at work to put his code reader on it to see if there were any codes stored in the computer even though the CEL is now off. This is what it came up with....

1. When it did it's diagnostic check of all the systems, all checked out fine except for "Catalyst Monitor." It continued to blink and never stopped, where as the others all eventually stopped blinking.

2. The code returned was P0420 which is "Catalyst System Efficiency Below Threshold (Bank 1)."

What in the world does this mean? Is it an oxygen sensor and if so, how do I know which one? If it were a bad catalytic converter, wouldn't I get more than one code (ie bank 1 and bank 2)? Thanks guys.

Matt

Uh oh....Just did a search (sorry guys, it's lunch and I was in a hurry and didn't think to search first) and found this thread...

https://www.yotatech.com/forums/show...tem+Efficiency

Looks like the same code I got and that guy refers to the problem being the cat with that code. Not good. The stealer quoted me almost $1,000 to replace the cat when they checked it last fall. Not gonna happen right now if it costs that much.

Matt

DIY for much less.

:guitar:

buy a magnaflow cat off ebay for ~60 and get it installed at a muffler shop.

Ditto.

i think its the cat, because when i did mine, it read :left bank sensor 2, and some other stuff, so the cat is probably clogged a little. good luck EDIT sorry i just now read the whole thread sorry

Double ditto... Click & save:
http://search.ebay.com/Carsound-Magn...ytic-Converter

I have had the same problem, with a twist.
Last summer my CEL went on and then again in November. When I got it cleared through my mechanic he said "catalytic converter."
The light did not come back on again for over a month, and when it did, same diagnosis.

I had the light cleared back around Christmas and has not been back.

Here is the twist...

All three times it went on I happened to be in Arizona. Flagstaff in September, I was at the Grand Canyon and Flagstaff over Thanksgiving, then visiting Prescott between Christmas and New year. I am wondering if they have a different blend of fuel there that is causing my CEL situation. Pretty strange...

Thanks guys. Three questions....

1. Will the "high flow" cat cause a change in the tone of my exhaust? I love it the way it is now.
2. Will a "high flow" cat produce any noticeable performance gains (other than clearing this code in the ECU)?
2. Which size do I need?

Thanks. Later.

Matt

Thanks MidiWall!!!!!

Matt

I had the same situation with my 4runner. Code P0420 came up a couple times and it ended up being the cat. If your 4runner is under 80K the cat is still under warranty and they should replace it for free, that was the case with mine. Does yours have the single or dual cat (California) system? If you ended up with a cali spec 4runner it might be a little more of a challenge to just add one high flow cat but I think others on this board have done it.

I know my truck was purchased in '99 in Cali but I don't think I have the Cali version as my mechanic told me that I can buy the "cheaper" 02 sensor. This was awhile back when I had basic maintenance stuff done. Does anyone know how you can tell which one you have?