K so a couple months ago my parents Mazda Protege 5 got a check engine light. We went to a shop to get it diagnosed and the guy at the shop told me it's the problem with the cat. We bought new cat and replaced it but today we drove it and the engine check light came on again.

We went to the shop and the guy said there are two cats on Mazda and the one we replaced was the main cat. He said the original diagnosis showed the main cat failed, so we had to replace it, but now the diagnosis is showing that pre-cat is not functioning well also. He went on and said something about how the computer diagnosis only shows if one of the cats is having a problem, but does not show both. He said when both cats have problem, it's only after we replaced the main cat, it will show if there is a problem with pre-cat as well.

Can someone familiar with this chime in to comment on this? Does it make sense?

Thanks in advance.

 

Isn't the cat free at Mazda? I thought they cover emission components for a while.

 

honda does like 100k miles and 8 yrs i believe

 

but isn't that with warranty?

 

I've had a Protege 5 and currently have a Mazdaspeed protege. He is correct on the Protege5, it does have 2 cats. It has the main cat after the header and then there is another cat on the midpipe. As far as his explination of narrowing down which cat it is, that sounds kind of odd. There should be a code for the front or rear cat, something along those lines.

Do you know what code the car is reading?

If it was P0421 then that is the "pre-cat" (bank-1) that comes off the header. Here are the details for the code:

"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)."

The problem could be that even tho the cat was replaced, the o2 sensors might also need to be replaced now.

Have them go to a local Autozone and have them run their OBDII tool and they will give you the code. Get that and I can get you more info.

 

This should be obvious, but stop messing around with a shop that obviously doesn't have the equipment or experience to properly service your vehicle. By the time you get done buying parts the problem should be solved, but if you are going to spend an open-ended amount of money anyway, go to the dealer.

 

I thought all cars came with at least an 8yr/80k mile emissions warranty?