P4020 - Catalyst Converter Below Efficiency Threshold (Bank 1)

[YMS1975]

So I got a P4020 code (Catalyst Converter Below Efficiency Threshold [Bank 1]). Is it safe for me to assume that "Bank 1" is the pre sensor, and not the the post?

Also, just to confirm....I want to make sure that there are only 2 oxygen sensors on my 2005 Grand Prix (Base Model).

Lil' help?

 

[matt5112]

The code is suggesting your cat is bad.

Nothing about the O2 sensors.

 

[BillBoost37]

And...your title is incorrect should be P0420

 

[sic6]

Make sure you don't have any exhaust leaks after the cat.
It will also throw a cat code.
Mine was leaking between the cat and rear o2 sensor.
Repaired the leak, code never came back.

 

[YMS1975]

And...your title is incorrect should be P0420

You're right....my bad. :th_embarassed:

 

[YMS1975]

Make sure you don't have any exhaust leaks after the cat.
It will also throw a cat code.
Mine was leaking between the cat and rear o2 sensor.
Repaired the leak, code never came back.

Cool.

I'll give it a look-see. If I don't see any visible leaks; then I guess I'll have to end up replacing it and the O2 sensors. I know the code has nothing to do with the 02 sensors (as matt5112 pointed out) but it's probably the original ones, so...while I'm down there. :th_crazy: