01droptopgt

Hey all i have a reoccurring problem with my with 01 Formula. Everytime i drive my formula for a short distance i get a ses light.
when i run the code on it it comes back either a code 411 or 421 one bank or the other shows to be out of emission range.
I had a another problem several months ago with a rear bank 2 o2 going out i replaced it and everything was fine till about 3 months ago and then this started this.
i clear the codes out by pulling the computer fuse under the hood leaving the fuse unplugged for about a hour or so then its good for awhile. i have noticed that it comes on more frequent when the gas is low in the car. it doesn't do it on the highway either. it's only when i 'm driving around town. and everytime i'm stopped at a light or something.

any ideas, suggestions,
Thanks, Charles

2001NBMZ28

Are you sure those are the codes? Don't see them thumbing through my helms.

01droptopgt

that was the codes Autozone gave me when i go to have the car scanned. and they go inside and tell me it's either one bank or the other reading out of tolerence on the emmisions. personally i think it might be a bad cat but the car still runs the same numbers at the track and gas mileage hasn't slipped cat isn't running hot or rattling,(you guys tell me) car runs good other wise. whewn it comes back on and it will i'll make sure of those codes.

waiting2bl33d

i could have swore that P0421 was an EVAP code. (could be wrong though) but have you checked gas cap?

01droptopgt

I looked at it awhile back but now that i think about it i might just go ahead and replace it just to cover my bases.
but its funny that it only really does it when its low on fuel.
which untill reently was most of the time with nearly 4 dollar a gallon Gas. now gas prices are better so i've been keeping more gas in it. thanks for the tip i'll replace it tonight.
Charles

01droptopgt

this is what i found on the obdII site and this is what came up and it is the same code. any ideas as to what the hell it means and what to do about it.
P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)
Help!!!!
Charles

1987firechicken

If that is really the code that is telling you a rear O2 is bad on the drivers side or more likely the driver side CAT is not working properly. Neither of these will really effect how the car will run unless the cat is clogged or broken some how it may restrict the exhaust a bit, but since you said it doesn't make noise I doubt it's broken up in there. Even though it might not be clogged though it's not operating how it should so the only way to get the code off and stay off is replacement of the cat and possibly the rear O2. If you live in an emmisions state you will fail the check since the code is in your PCM.

2001NBMZ28

Any chance the codes are P0410 and P0420? 411 and 421 are generic codes for GM Ford and Chrysler.

ghardester

Po411=Secondary air injection system incorrect flow detected.

P0421=Warm up catalyst efficiency below threshold (bank 1)

Just in case they transposed the 421, 412=Secondary air injection system switching valve A circut malfuntion.

01droptopgt

I'm almost sure and the wife says she thinks it's 421 but i really can't be sure until it comes back on again i drove it all weekend and it never once come on. LOL figures. but when it does i'm going to Autozone and get it scanned but both of us are almost sure thats the code. It seems like it only comes on when the car gets low on gas and it's not low YET it will be soon though.