Check engine light Stays on

Getting a PO421 code? Is this a bad CAT?
Car is sonata 2002 with a 2.4L with 94k miles. In the last 3,000 miles
have had tune-up,new timing chain,new water pump.I understand CAT are
expensive for this type of vechile.

 

Most likely, yes, you need a manifold catalytic converter. Check for
exhaust leaks and proper oxygen sensor operation. If oxygen sensors are
working properly and there are no exhaust leaks, replace the converter.

 

Lucked out new gas cap did the trick.
Happy Holidays

 

A new gas cap won't cure a P0421. What makes you think you've fixed the
problem?

 

After looking back, I see the tone of the previous post appears abrasive.
It wasn't meant to be. I am indeed interested in why you believe the car
is fixed. Did the lamp go out? Did you turn it out and it didn't come
back on?

 

Lamp went out and hasn't come back on.

 

Lamp went out by its self and has not come back on.

 

Chances are your catalytic converter is at marginal efficiency. The lamp
will probably come back on sooner or later, with the same code.

Since it went out on its own, disconnect the negative battery terminal for
about five seconds to clear the code (presuming you're outside the 8/80
warranty period). If you're still within the warranty period, present the
car to the dealer for service, hopefully while the code is still present in
memory.

 

I'll keep you posted.
Foot Note: Local newspaper article said certain individuals are stealing
CAT for metal value?Some can be taken within minutes.