ck egn light

I have a 1997 Pontiac Grand Am with the 2.4L 4 cylinder engine. My check engine light came on and when I had the code read I was told it was P0420 catalyst threshold low bank 1. My chilton book tells me TWC System low efficiency Bank 1. Can you tell me what this means. Thanks.

are you using a code reader from a dept store , like the ones that come with a booklet that tells you the expaination for code numbers?

are you using a code reader from a dept store , like the ones that come with a booklet that tells you the expaination for code numbers?


No I went to Autozone and had the code read.

i got the same code. i put a new O2 sensor and had it reset, the CEL came back on, so i just let it go over the winter. about a week ago i moved my battery to the trunk, which made me have to disconnect the battery for about 2 hours. and now it hasnt come on.

So you might want to change the O2 sensor on the downpipe, then unhook your battery for say an hour or 2. if it comes back get it scaned again.

Also when you change it your going to have to get an O2 sensor tool, i payed $10 for one used it then put it back in the box and returned it, you can get this from autozone too.