code 421 - clogged cat? sensor?
 

High all. Last night my CEL came on and today I stopped at autozone to have them pull the codes. Turns out to be 421. (now I thought he told me it's 420, but on the printout he gave me he marked 421, and he did mention warm up something, so it's prolly 421 :s )
"Warm up catalyst efficiency below threshold (bank 1)"

They told me it was probably a clogged catalyc converter or sensor in it or something. The previous owner had a different exhaust system on the car with headers and intake. The dealer I bought the car from put stock parts back on the car. I wonder if that voided the warranty in that area. I am having my A/C fixed under warranty probably this week (part on order). What should I do? I would like to put a decent (not loud, just mean and pretty) exhaust system on it but I've never dealt with this stuff. So I'm looking for your recommendations.

The guy at autozone asked me if the car is a little slow when I step on it and it is. Seems to me at least. He said it's because the air isn't getting out right probably. I guess due to a clogged cat. Any advice/recommendation is welcome guys. Thanks!

I suppose the cat could be clogged, it was off the car, and no telling what made a nest in it when it was in storage. Most likely, whatever it is would get burned out the first time they started the engine after reinstall. I would check the o2 sensor, look and see if they did another country-ass wiring job on it like your MAF, or damaged it on reinstall.
I'm talking about the "pre cat" , the one that's up front just below the exhaust manifold. If they had a header on it, they would have taken it off.

Ok I will check that. But I had my A/C fixed today by the Mazda dealer and asked them to look at the CEL code too. They think the problem is in the MAF. Because it's cracked on the side where the wires go in. I'm going back to where I bought the car to see if they can do something for me. Mazda won't cover it under warranty because it's cracked. If it was just malfuntioning then they could send it off for a new one. That's what they told me anyways. I'm glad the A/C got done under warranty though.

i had this same code pop up on me 2 weeks ago i took it to a local garage they said it had to be the HO2. i replaced my HO2 (the one on the front of the engine) i got my HO2 from a junkyard off of an 03 protege, cel was back on by the end of the day....went to autozone had it checked same code!!! what should i try next any suggestions??

try using a sensor thats NOT from a junkyard parts car.

im pretty sure the sensor is good but im gonna take it back to the shop and have them check it out again. where can i find a good sensor for a reasonable price?? they quoted me 260 bucks for one.....thats y i went to the junkyard!!

My code stayed away when a Mazda dealer replaced the cat. conv. It was done under warranty for me. They tried things but like you the code came back the same day or within a couple of days.

The convertor is covered for 8/80 on all US cars.

I can run the VIN to check the warranty start date.

Mark, is that 8/80 for ALL manufacturers?? I seemed to remember something about all manufacturers having the same emissions equipment warranty.

when my wife's 99 mustang was 3yrs old the exhaust broke in half right at the cat and Ford said it wasn't their responsibility. We sold it and bought an RX8.

I'm sure Ford covers converter failure for 8/80. I did hear they were talking about making it an even 10 years in California but I'm not sure if that happened.

It could be the same code I just had but I am not sure. My cat is being replaced because the code I just got saying the second O2 sensor was getting a inconsistent reading. Go check out the dealer first and don’t let them tell you they will still charge you for pulling the code. I had a huge fight with my dealer about this because I feel if the code is from a warranty issue I should not have to pay….and I won!!!!! Also i was told that if the sensor is bad it will also be replaced under the emissions warranty.