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P0420

Tiny
TALLMAN1781
  • MEMBER
  • 2001 GMC SONOMA
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 95,000 MILES
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?
Monday, December 13th, 2010 AT 1:54 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 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
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Wednesday, December 15th, 2010 AT 4:48 PM

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