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Check engine light on after repair, codes PO300, PO300 and PO171

Tiny
3RDMRWILLL
  • MEMBER
  • 2003 GMC YUKON
  • V8
  • 4WD
  • AUTOMATIC
  • 255,000 MILES
Check engine light still on after repair and the truck is running great, but light still on. Help! Replaced eight coils, eight spark plug wires, and replaced eight spark plugs. Codes po300, po300 and po171.
Tuesday, January 22nd, 2019 AT 11:58 AM

3 Replies

Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny
The code P0300 Was for a random/multiple misfire that sounds like was fixed when you changed the plugs and coils, But, The Code P0171 is for a Bank 1 system too lean. That usually means there is a vacuum leak or and alternate way that air is leaking into the engine and being burned during the combustion process.I've attached pictures below as a step-by-step guide to help diagnose the problem. Hope this helps and thanks for using 2CarPros.
Danny-
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Wednesday, January 23rd, 2019 AT 1:43 AM
Tiny
3RDMRWILLL
  • MEMBER
  • 2 POSTS
Po171, was, bcz of the po300, I fixed po300, than, drove one driving cycle, now truck runs great and check engine light is no longer on. All is well
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Friday, January 25th, 2019 AT 5:31 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,443 POSTS
Thank you for the reply. Many people just leave without saying if they were able to repair the issue or if anything. Please return anytime with your automotive related questions.
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Sunday, January 27th, 2019 AT 11:34 AM

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