P0420

2001 GMC SONOMA
95,000 MILES • 4 CYL • 2WD • AUTOMATIC
Avatar
TALLMAN1781
  • MEMBER
  • 1 POST
i have a 2001 gmc sonoma 2wd 2.2 liter and have the P0420 code for catylyst efficiency low bank one.. i have a new cat and rear O2 sensor so what else could be causing this?
Dec 13, 2010 at 1:54 AM
Advertisement
Avatar
JACOBANDNICKOLAS
  • ✓ASE Certified Mechanic
  • 110,194 POSTS
  • ASE Certified Mechanic
Have you checked for vacuum leaks? Have you checked the wiring to the O2 sensor to make sure it isn't damaged or corroded where it pluggs into the O2 sensor?

Let me know.
Joe
Dec 15, 2010 at 4:48 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.