0421 Bank 1 Code Issue

[Cardriver]

Great info on the 421 Bank 1 code! Can anyone give me some more detail?

I have had the engine light com on 3 times in the last 1.5 years. 2 of them were o^2 sensors that were replaced under warranty. Now (6K miles after the warranty has run out) the engine light came on again. I read the code and it is coming up as 421 Bank 1. I understand that this is probably another o^2 sensor, but need some detail to diag and fix it.

Does anyone know which sensor is identified by "bank 1" and whree this sensor is located? Additionally, I read that there is a universal sensor that can be used as a replacement. Where can I purchase one and is it the same part for all 4 o^2 sensors?

Thanks for the great discussions!

[Cardriver]

Hello Again,

I was told by one of the parts guys @ Autozone that "Bank 1" identifies the drivers side sensors. If this is true, it narrows my search down to two sensors. Can anyone validate this for me?

Thanks!

[///BHRpowered]

wrong. lucky for you I actually had this replaced under warrenty and they just finished this morning, this is what is on my invoice. "customer states check engine light has come on, engine code P0421 has appeared in computer. this is bank 1 warm up catalytic convertor malfunction. replace under federal warrenty 80k/96months. systems diagnostics reference #127425, bank 1 warm up catalyic convertor below efficency limit. F0008XDX//1.5 F0702//1.4.

that came staight from browns fairfax mazda. all cars sold in the u.s have a federal emissions warrenty of 80,000 miles and 96 months, just go to a mazda dealershi and they'll fix you up, took me 2 days though

[Cardriver]

Wow! That is awsome information. I will take it to my trusty dealership and let you know the results!

[///BHRpowered]

glad to help. they'll probably tell you it takes half a day to do, but don't listen. for some reason alot of the bolts and stuff just suck ass and have to be cut off, atleast thats how mine was (2000) so it takes alittle over a day

[mannboy2]

I have been through 4 o^2 sensors since I bought this car , One year ago. Now the Check engine light is on again...back to the dealer I guess...
This will be the 5th time in a yr ..anybody know what the deal is with this problem...(Bill Gatton Mazda in Johnson City TN has replaced sensors for me and it's never cost me a dime..but It's getting to be a pain in the butt to keep taking the car back every other month to fix it) 67,000 miles on vehicle now...

[///BHRpowered]

Id let another dealer fix it. for all you know there not even fixing it. just resetting the computer

[///BHRpowered]

or your 1 of those people who always rides around on less then a quater tank of gas, anything less then a quater is really bad for your fuel system, and less then that is havoc on any cars o2 sensors

[mannboy2]

Now come on guys I'm smarter than that...I know the mechanic who did the work... 4 o^2 sensors and a bank 1 cat.convrt. replaced so far...I reset the check engine light myself twice...and it comes on within 2 min of starting the engine...sounds like the bank two cat.convrt has probably gone out this time. (rotten egg smell).
as for the 1/4 tank thing...Amoco Premium Fuel only and very rarely does the tank get below 1/2 tank...
I believe there is something wrong with the emissions system on this car and probably all Millenia S' s that Mazda needs to find a solution to. I love this car and plan to keep it. Are 3 Cat Converters really necessary, seems like overkill to me....

[///BHRpowered]

perhaps you shoud let the dealer do it, plus reseting the engine light yourself??I wouldn't