Engine trouble code

Tiny
PARAINES
  • MEMBER
  • MAZDA PROTEGE
97 mazda protege, 156000 mi. Does a p0420 code means that I will eventually have engine failure or does it mean that I need to possibly get a tune up after the repair of my vehicle?
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Monday, March 5th, 2007 AT 10:19 AM

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Tiny
INDYUKE
  • MEMBER
No, it does not mean you will have engine failure. Your engine will be just fine. The definition of that code is, "Catalyst system efficiency below threshold on bank 1".

Meaning, you have two oxygen sensors in your car, one before the catalytic converter and one after. The problem will probably be between the two. Notably that the catalytic converter isn't burning off the extra hydrocarbons like it's supposed to and thus keeping emissions down.

Your catalytic converter could be bad, could have a hole in it, or one/both of the oxygen sensors could be reading the exhuast stream wrongly.

There is a mazda guy here who is pretty good. He could tell you if what you have is a common problem for your type of car or not. I hope this helps.
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Monday, March 5th, 2007 AT 10:49 AM
Tiny
COSMO
  • MEMBER
Hello,

p:0420 is a Cat below efficently threshold code. More than likely the front cat has gone bad on your car. You can confirm this through monitoring both front and rear 02 sensors and checking the 'wave' pattern.

However. IF you have a 1.5L motor, have someone check the exhaust manifold for cracks (have to check from under the car). There are cases of manifolds being cracked, causing cat and 02 sensor codes.

Cosmo. Mazda TEch
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Tuesday, March 6th, 2007 AT 5:44 AM

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