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Engines codes

Tiny
BILLB55
  • MEMBER
  • 2003 GMC SIERRA
  • V8
  • 2WD
  • AUTOMATIC
  • 72,000 MILES
Codes PO171&PO174. Just replace MAS about a week ago with a reman. Check engine light is on again. Reading the codes above. What should I check next. Changed plugs and wires less than 20,000 miles ago.
Thursday, January 13th, 2011 AT 10:27 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
The codes indicate a lean mixture on both banks of the engine. Check for vacuum leaks first. Check fuel pump pressure. A restricted fuel filter can restrict the fuel supply. Go to our homepage under the DIY section for direction to check fuel pressure. My first guess, however, is a vacuum leak.
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Tuesday, January 18th, 2011 AT 9:28 PM

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