CODE P0421 ON MAZDA 626

I HAVE A MAZDA 626 WITH ONLY 67,OOO MILES. THE CHECK ENGINE LIGHT IS ON AND WHEN I TOOK IT TO AUTO ZONE FOR TROUBLESHOOTING THE CODE WAS P0421. DEFINITION-CATALYST EFFICIENCY LOW-BANK 1. EXPLANATION-THE OXYGEN SENSORS MONITOR THE CATALYTIC CONVERTERS ABILITY TO STORE OXYGEN. PROBLEM CAUSES- 1. CATALYTIC CONVERTER DEFECTIVE (FAILURE POSSIBLY DUE TO #2,3, OR 4) 2. ENGINE MISFIRE OR RUNNING CONDITION. 3. LARGE VACCUM LEAK 4. ENGINE OIL LEAKAGE INTO EXHAUST-VALVE GUIDE SEALS, PISTON RINGS. THE PCM HAS DETERMINED THAT THE WARM UP CATALYST EFFICIENCY FOR BANK 1 IS BELOW TRESHOLD FOR THE CURRENT ENGINE OPERATING CONDITION. (BANK 1 IDENTIFIES THE LOCATION OF CYLINDER #1, WHILE BANK 2 IDENTIFIES THE CYLINDERS ON THE OPPOSITE BANK). I HAVE REPLACED THE SPARK PLUGS AND WIRES AND RESET THE CHECK ENGINE LIGHT. IT CAM BACK ON THE OTHER DAY I NOTICED WHEN I CUT ON THE AIR CONDITIONER. THE CAR DOES NOT SMOKE AT ALL AND IT SEEMS TO BE RUNNING WELL. I JUST BOUGHT THIS CAR 2 WEEKS AGO, PLEASE TELL ME I DIDN'T BUY A BIG PROBLEM AS WELL. THANK YOU!!!!!!

I'd return to who sold it to you! The conveter could still be under warranty!

IT WAS SOLD AS IS FROM THE USED CAR DEALERSHIP. NO WARRATY!

No factory warranty remaining? Some converters are covered for quite awhile! I'd take it to a Mazda dealer at this point and check!

How long is your emissions warranty? Sometimes converters are covered under that (as opposed to the bumper-to-bumper warranty).

You didn't say what year your car is so we just have to guess on that

I'M NOT SURE WHAT KNID OF WARRANTY IT MAY HAVE. I BOUGHT IT FROM A USED CAR DEALERSHIP AND I DON'T KNOW HOW EXACTLY TO FIND OUT IF IT DOES HAVE A WARRANTY. THE CAR IS A 2001 AND IT SEEMS TO BE DRIVING FINE. I SOMETIMES NOTICE A SMELL COMING FROM THE HOOD. MY HUSBAND LOOKED AT IT AND SAID THERE WAS OIL CAKED UP WHERE THE GASKET COVER IS ON THE TOP OF ENGINE. HE HAS ORDERED A GASKET VALVE COVER SET FROM ADVANCED AUTO. I AM HOPING IT IS THIS GASKET AND NOT THE HEAD GASKET. IT DOES NOT SMOKE THOUGH SO, I AM THINKING IT IS SOMETHING MINOR. I HOPE!!!! ANYMORE INFORMATION YOU CAN GIVE WOULD BE HELPFUL. THANK YOU:)

Jeepers call the MAZda dealer with the vin # and mileage and they'll tell you if there's any warranty left! In fact pay them to check the whole vehicle out including your oil leak and while you're there they'll tell you if the cat is required, covered etc!

I have a 2001 Mazda 626 also, the check engine light was on, so before i went to inspection i replaced the oxygen sensors, and the catalytic converter. The mechanic reset the computer but the check engine light still comes on, I do not know what else to do. Also the mechanic cleaned out the egr valve and replaced the fuel filter. Any suggestions? It has 108000.00 miles but runs great. Oh yea when the computer was tested the code PO421 still appears.

Have you contacted the dealer for warranty information, like COMP said?