My 2002 Pro5 Check engine light has come on and the car has a definite loss of power.
Went to Autozone and they came up with Engine code PO421 -"warm up catalyst below threshold"
He then tried to sell me a new O2 sensor for $250.
Any help or ideas?
Thanks, Pat

 

It could be the same code I just had but I am not sure. Mazda hase a 120,000km 8yr or is it a 128,000km 8yr emissions warranty. 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!!!!!

 

yo, just going through the forum to try and solve my problem. my O2 sensor went bad and wether i change the one after or before the catalyc converter, they are about $200 each. so my question to your thread is, you are saying that the emission warranty is for 8 years - 120, 000 km but all my factory warranties experied already, can i still get this one? i really dont want to spend all that money on a tiny *** sensor. please get back to me, thanks

 

P0421 simply means the first O2 is too close the reading of the second O2. Changing the sensor would be like shooting the 6 o'clock news guy when he is just reporting.

You need a new convertor. The parts and labor are covered for 8 yrs and 80,000 miles.

 

Exactly. This is a government regulation relating to emissions standards. ALL cars sold in the US are required to meet the 8 yr, 80,000 mi requirement.