Please Help! 2000 Mazda 626 LX?

[lingsuie]

I just bought used car from auction. I tried to do small tune up with it, change spark plug, air filter. Car runs good. All look ok until check engine come up and it failed inspection. Code P0421, I know when I try to researched it, it mean catalyst problem. But someone else recomend to disconnect the negative cable of the battery to reset it. I disconnect it, check engine light went off. I drove for about 15 miles to work, and on the way back, check engine light come back on.



I don't know what else to try first before take it to mechanic. Because I just move and didn't have the budget to fix the car.



Can someone please advise what to try first before taking it to the mechanic?



ThankS

[LeeH]

I believe a catalyst problem is your catalytic converter. If it is that, it will need to be replaced before your car will pass emissions. It is fairly expensive. I'd say $300-$500 including labor.

[MrM]

sounds like an emmissions problem.  Maybe a problem with the catalytic converter

[MichaelScosyrev]

cat converter is rarely the problem, usually it's due to incomplete combustion. do a reasearch on google how to pass the smog test.



usually you would start with replacing all filters, plugs, wires, distributor rotor, clean the throttle body, check or replace the oxygen sensor, change oil! thats a big one, and have the fresh fuel in the tank before taking the test.



also make sure the car is really warmed up as even newer cars will fail the test when cold.



good luck.

[hey_yall]

you have a cat monitor which is a oxegen sensor behind the cat. converter that could be failing but they arnt to cheap but cheaper than replacing the cat.

[ponce_76us]

it will keep coming on untill you fix the sensor and or the catalystic convertor, only then do you reset it. gd lk.