03 Tahoe catalyst monitor not ready

[Delta_Dave]

I have an 03 Z71 with the 5.3. Several months ago the battery went dead and I had to replace it. I want to sell it but I keep getting told the catalyst monitor is not ready. I have done the GM drive cycle (55 mph for 5 minutes, etc.) and driven it round trip 100 miles twice (primarily freeway, maintaining 55 mph on and off). Probably about 220 miles since I replaced the battery. Still cat monitor not ready. Techs say keep driving it / do drive cycle. No codes of any type.

Some history: My teenager was going to use this Tahoe for his daily driver. He cut the muffler off behind the cat to make it loud. Can a missing muffler reduce back pressure causing the cat monitor to not become ready? He also put in a cold air intake and took it off. I noticed the clamp where the MAP connects to the filter box was loose. Can that cause a cat monitor not ready?

Any other suggestions besides "keep driving it"? It's old and I really don't want to have to keep driving it to work, I just want to get it smogged and sell it. Thanks in advance!

 

[HiHoeSilver]

I have an 03 Z71 with the 5.3. Several months ago the battery went dead and I had to replace it. I want to sell it but I keep getting told the catalyst monitor is not ready. I have done the GM drive cycle (55 mph for 5 minutes, etc.) and driven it round trip 100 miles twice (primarily freeway, maintaining 55 mph on and off). Probably about 220 miles since I replaced the battery. Still cat monitor not ready. Techs say keep driving it / do drive cycle. No codes of any type.

Some history: My teenager was going to use this Tahoe for his daily driver. He cut the muffler off behind the cat to make it loud. Can a missing muffler reduce back pressure causing the cat monitor to not become ready? He also put in a cold air intake and took it off. I noticed the clamp where the MAP connects to the filter box was loose. Can that cause a cat monitor not ready?

Any other suggestions besides "keep driving it"? It's old and I really don't want to have to keep driving it to work, I just want to get it smogged and sell it. Thanks in advance!

Do you have a way to check for codes? Did your kid mess with the post cat o2 sensors when he chopped the muffler?

 

[Scottydoggs]

if he cut the pipe off close to the rear o2 sensor that could be possible.

but really, daily driving it is the only way to get it to become ready.

i reset codes a week or two ago on my 05. i dont drive it much at all, just sundays, but i took it for a road trip of a 100 miles or so each way to take my friend to pa to buy a hellcat charger. i checked if my pcm was all ready yet when i got home and my evap is still "not ready". thats 200 miles at 80 mph both ways. and i got gas so the level dropped pretty good. thats one of the things the evap test looks for.