P0420

2001 GMC SONOMA
95,000 MILES • 4 CYL • 2WD • AUTOMATIC
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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 12, 2010 at 5:54 PM
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JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
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 8:48 AM
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