Code P0420A

[davbell22602]

97 K1500 5.7L

Whats causes a P0420A to trip a SES light? It only came one once. Hasn't came one since I did the BG induction clean on the engine top end.

 

[Kennyray]

P0420​

Catalyst System Efficiency Below Threshold (Bank 1)






​

 

[davbell22602]

P0420​

Catalyst System Efficiency Below Threshold (Bank 1)






​

So is my 2 kats going bad or did they just get clogged up a little? Still have factory Kats on it @130K. I have no Y pipes. I have dual pipes to muffler then single tail pipe.

 

[Kennyray]

Could also be a bad oxygen sensor.

 

[Boilerup15]

If you still have original cats, I'm guessing that are starting to fall apart on the inside.



Or what Kenny just said.

 

[Kennyray]

I had the original cat on my 1500 and it had almost 240,000 miles on her with no codes.

 

[Boilerup15]

I had the original cat on my 1500 and it had almost 240,000 miles on her with no codes.

Impressive.

 

[Kennyray]

It's all in the maintenance.............

 

[daddy]

Kould be the kats.

 

[DV2000NJ]

Also check for an exhaust leak before the downstream oxygen sensor.