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P0420

Black Mamba

By Black Mamba
in Engines & Drivetrain

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14burrito Enthusiast

14burrito

Posted
Posted

Cat efficiency below threshold. Figure out what bank first. Swap post cat O2 side to side: does the efficiency fault follow the sensor or remain in the original bank?

 

If remains, look into your cat.

If it moves, replace the O2 sensor. 

14burrito Enthusiast

14burrito

Posted
Posted
1 hour ago, Black Mamba said:

So...if i replace both upstream 02 sensors & the fault  remains, then it's defintely CAT(s) ?

 

Why would you mess with upstream sensors?

 

Upstream = AFR; downstream = cat efficiency.

 

Your fault is a downstream. 

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted

Why fix any of it?

 

If the truck runs fine, just forget about it.

 

Are you trying to save the environment?

 

Trying to pass emissions?

 

 

People in my area spend $2,000 to replace defective catalytic converters when the car runs fine, and emissions testing stopped being required in this state years ago.

14burrito Enthusiast

14burrito

Posted
Posted
1 hour ago, Supreme Pizza said:

Why fix any of it?

 

If the truck runs fine, just forget about it.

 

Are you trying to save the environment?

 

Trying to pass emissions?

 

 

People in my area spend $2,000 to replace defective catalytic converters when the car runs fine, and emissions testing stopped being required in this state years ago.

 

While I dont necessarily disagree, why not fix something that might be an easy fix. Diagnosing a bad O2 is relatively easy, Cheap to replace. I mean ******, for all we know a rodent might have eaten the harness.

 

He also didnt mention if it's a hard/active fault causing an MIL.

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted
34 minutes ago, 14burrito said:

 

While I dont necessarily disagree, why not fix something that might be an easy fix. Diagnosing a bad O2 is relatively easy, Cheap to replace. I mean ******, for all we know a rodent might have eaten the harness.

 

He also didnt mention if it's a hard/active fault causing an MIL.

 

 

That's true, and I agree. If its something simple - why not fix it. But I would not waste money taking it to a shop or replace the cats or anything.

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

If the fault stays on that side I'd just space the o2 sensor out of the exhaust some, it may stop the light from coming on and it's a very cheap fix.

 

Plus he can continue to use the remote start if his truck has one because that stops working with an active CEL.

  • 4 weeks later...
TJay74 Senior Enthusiast

TJay74

Posted
Posted

the OEM cats are covered 8yrs/100k per Federal Mandate.

Also a P0420/0430 can mean a clogged cat, a clogged cat can get really hot and possibly start a fire. No matter if they are inspecting or not where you live, it get the issue fixed (replace the offending cat) or delete the cat (harder to do now since HP Tuners doesnt offer the ability to delete cat codes anymore).

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