Mazda MPV This minivan was among the class leaders with its roomy interior and efficient powertrain.

2000 Mazda MPV throwing po421

Old 01-12-2007, 05:19 PM
Thread Starter
Join Date: Jan 2007
Posts: 1
Default 2000 Mazda MPV throwing po421

I am checking out a friends mazda mpv for a friend etc.... Its throwing a PO421, which says its slow to come to temp for catalyst system.

I've heard people definatively say its a bad cat, and others claim its the o2. Can anyone provide any sort of insight or experience with this particualr prob?

Thanks in advance!
Old 01-12-2007, 07:36 PM
Senior Member
Join Date: Jul 2005
Posts: 2,747
Default RE: 2000 Mazda MPV throwing po421

Van must be a California level emission to set a P0421. This code is indicating that the Right side bank front warm-up catalytic converter is below efficiency limit. This converter is built right into the right side exhaust manifold (Right side being closest to firewall, Left side is closest to the radiator). Have yet to see an oxygen sensor problem that would set a Cat efficiency code such as that. Make sure that there are no exhuast leaks from the manifold or outlet gasket area though as this has been know to throw a false code.
What kind of mileage is on the van? That part would still be covered under emissions warranty of 8 years or 80,000 mile so hopefully it is as a new one will set them back almost $900 for converter and gaskets, let alone labor charges as they are a bugger to get to.
There is a way to check yourself by monitoring the right downstream oxygen sensor signal voltage with a voltmeter if you are interested in trying to do that.
Old 01-23-2007, 01:14 PM
djn is offline
Join Date: Jan 2007
Posts: 24
Default RE: 2000 Mazda MPV throwing po421

I think babyhuey nailed it. I had the same error code on my 2000 MPV (although I'm not in California). I have 170K miles on mine. Just took it to the dealer yesterday. Right exhaust manifold is cracked, which they said is most likely causing the reading. O2 sensor is bad too. Total bill for manifold & O2 sensor with labor is about $1,500. My manifold crack is bad enough that you can hear a "puffing" sound in the engine when it starts. Good luck with yours.
Related Topics
Thread Starter
Last Post
10-28-2012 08:29 PM
Mazda Protege
12-20-2010 01:01 PM
Mazda MPV
05-22-2010 07:01 PM
Mazda Tribute
03-14-2009 09:48 AM
Mazda Protege
01-08-2009 03:21 PM

Thread Tools
Search this Thread
Quick Reply: 2000 Mazda MPV throwing po421

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.