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skylark: buck..check engine light..efficiency below..below threshold

 
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  • Answered by:eric
  • Automotive shop manager
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  • Accepted Answers: 521
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Customer Question

i have a buck skaylark 1997 the check engine light is on anmd the ets light i had the code read and it was 420 catalys systems efficiency below threshold (bank 1) how do i fix it

 

Optional Information:
Year : 1996
Make : Buick
Make (other):
Model: skylark
Engine: 4cly

Already Tried:
nothing yet

Submitted: 1143 days and 18 hours ago.
Category: Buick
Value: $9
Status: CLOSED

Accepted Answer

Picture
Expert:  eric replied1143 days and 17 hours ago.

Hi,

 

DTC P0420 - catalyst efficiency below threshold is caused by only three things:

  • faulty catalytic convertor
  • exhaust leak between the exhaust manifold and convertor
  • Downstream(behind convertor) O2 sensor wiring damaged

check for exhaust leak between exhaust manifold and convertor and repair as necessary. If ok, check wiring harness on O2 sensor for damage- melted from touching exhaust, cut or chaffed wiring. Repair as necessary.

 

If the above are ok, replace catalytic convertor.

Expert TypeAutomotive shop manager
Category: Buick
Pos. Feedback: 96.3 %
Accepts: 521
Answered: 4/1/2010

Experience: over 20 years experience as a Automotive shop manager and tech/JA Mentor

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