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Code Po 420

sawdust2

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sawdust2 New Member

sawdust2

Posted
Posted

My 2003 silverado 2wd 4.8 L engine with 130,000 miles . It keeps getting code po 420.

Will I have to replace the cat., or could it be something else wrong.

 

thanks for the help.

WilliamBos Senior Enthusiast

WilliamBos

Posted
Posted

We had a bad O2 sensor front 1 bank 1(front drivers side) and because of it we had to replace the Y pipe, fried the Cat(s), but thankfully that was covered under Federal Emissions Warranty.

 

You made need a Tech II to read the parameters.

 

Good Luck. Keep us posted.

 

 

 

 

My 2003 silverado 2wd 4.8 L engine with 130,000 miles . It keeps getting code po 420.

Will I have to replace the cat., or could it be something else wrong.

 

thanks for the help.

  • 1 year later...
SOL12LUNA Enthusiast

SOL12LUNA

Posted
Posted
What kind of cat u use and did code went off?

 

My 2003 silverado 2wd 4.8 L engine with 130,000 miles . It keeps getting code po 420.

Will I have to replace the cat., or could it be something else wrong.

 

thanks for the help.

frdfandc Enthusiast

frdfandc

Posted
Posted

P0420 is a Catalyst Efficiency code. With that many miles on it, I'd suspect a catalytic converter.

 

What is happening is the O2 sensors have similar readings. The converter is not working as efficiently as it should be.

 

What I have had to do in the past is replace the cat and all O2 sensors. No sense in installed old sensors on a new cat.

05GMCZ71 Enthusiast

05GMCZ71

Posted
Posted

Darin is correct, but you should also have the vehicle diagnosed to make sure nothing else upstream of the cats and 02 sensors are causing the Cat and 02 Sensor to go out. Otherwise, your just throwing money away and the problem will reoccur.

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