1996 Chevrolet Suburban P0420 – Brakes Pulsate

My 1996 Chevy Suburban has a code Code P0420 code and bad sensors showing on code with large vacuum leak. I’ve sprayed carb cleaner all over the intake and brake booster house and all other vacuum lines and found nothing. I don’t know what else to do.

First of all the code P0420 is for a bad catalytic converter. Why do you think you have a large vacuum leak?

I gathered that much when I looked under there and seen one missing with a flex pipe in it’s place. I don’t know why I have a large vacuum leak.

Do you have a leak, or just assuming you do?

The code read it with the low emissions.

What was the code? Your year Suburban does not have a specific code for a vacuum leak??!!

It didn’t say. Sorry not trying to be bothersome.

Well then you might be chasing nothing at all. I would definitely get a catalytic converter put on it!

Just said large vacuum leak. It was at Autozone.

Yeah Autozone people pretty much know nothing about vehicles, and their scanners are junk. You may be confused…it may have been a large EVAP leak. That is a probable code for your truck. A code P0455.

I’m taking it to a gm mechanic when I get taxes.

Great idea !

1999 Chevrolet Suburban

1999 k2500 Suburban, had power assist for brakes and master cylinder replaced. When diving interstate speed for at least 15 miles start feeling pulsating as if tires suddenly out of balance. When braking to slow down severe vibration until below sixty or so. Does not happen at slower speeds and symptoms disappear. Mechanic cannot find a problem.

ProTech: Warped brake rotors will give the the pulsation when braking, but if they are bad enough, that can also cause the vibration when driving. Have the brake rotors checked. You may have a caliper that is locked up or brake hose restricted interanally causing the pressure to not be released to one caliper.