2002 Other Chevrolet Models catalyst system

2002 CHEVROLET
Avatar
TERRYTEA
  • MEMBER
  • 1 POST
2002 Other Chevrolet Models 4 cyl Automatic

my check engine light was on. it came back as code
po420 catalyst system efficiency below threshold
bank 1 so i had a new catalytic converter put on
a month later my check engine light is back on with the same code
any idea why? i also had the 02 sensor replaced
Oct 11, 2008 at 2:49 PM
Advertisement
Avatar
BLACKOP555
  • ✓ASE Certified Mechanic
  • 10,386 POSTS
  • ASE Certified Mechanic
try a new o2 sensor also check for exhaust leaks.

if the o2 sensor that monitors the catalyst efficency has failed will throw that code.

also if the pre cat one or sensor one that monitors and adjusts the fuel has failed it may screw up the reading of the sensor 2 that mnoitors the convertor. or it may have to rich a fuel mixture and cuasing the convertor to get too hot and burn out.
Oct 11, 2008 at 3:56 PM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.