2003 Pontiac Vibe 2003 Vibe P0420 code

Tiny
TOY-8844
  • MEMBER
  • 2003 PONTIAC VIBE
  • 4 CYL
  • 2WD
  • MANUAL
  • 220,000 MILES
Hey, guys I replaced the trans. Bearings, took car for a ride, the engine light came on, I pulled the code p0420 cat. Eff. Below threshold bank 1.I took the cat. Out and it was clean could see light through.I removed code, comes back at the same time every time, 40min. Of driving on hiway, I wil replace 02 sensors next, any ideas thanks
Saturday, April 4th, 2009 AT 9:56 PM

7 Replies

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
O2 sensors would be the logical assumption, if CAT is not clogged.
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Sunday, April 5th, 2009 AT 8:07 AM
Tiny
TOY-8844
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Replaced both 02 sensors, works great, bought both for 60.00 $ canadian from global-automotive from ebay brand name is Delphi, thanks guys for the tip
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Saturday, April 11th, 2009 AT 7:22 PM
Tiny
MMPRINCE4000
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Great news !
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Sunday, April 12th, 2009 AT 6:31 AM
Tiny
KAMLOOPS
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I have this same error code, I have 120,000 KM and the Cat is warranted until 130000km or 8 years

Should I take it the the dealer, or replace both o2 sensors first just like you did?
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Thursday, April 23rd, 2009 AT 11:43 PM
Tiny
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Replacing the O2 sensors is a logical step, but also check the CAT like previous poster.
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Friday, April 24th, 2009 AT 6:35 AM
Tiny
KAMLOOPS
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Its a 2003 but the cat is still under warrenty. I just dont want to take it to the dealer and then they tell me no its not the Cat and then charge for o2 sensors that I could replace myself.
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Friday, April 24th, 2009 AT 9:44 AM
Tiny
MMPRINCE4000
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The dealer will normally check the CAT by doing a backpressure test, where they remove one of the O2 sensors and install a fitting to a gauge to test for excessive backpressure.

If CAT is not bad, you are under no obligation to have them replace the O2 sensors, just tell them you want a backpressure test performed, get results and go from there. You will, of course, have to pay for test.

OR, remove CAT yourself (it's bolted on) and inspect for black soot, melting, cracking.

Handle CAT carefully, DO NOT DROP IT.
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Friday, April 24th, 2009 AT 10:55 AM

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