SES Light Fuel system lean codes?
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, SES Light Fuel system lean codes? in Past Cadillac Vehicle Discussion; Hey guys thanks with the help on that iac valve seems to make her start up fast anyway anoher thing ...
  1. #1
    SGWORLDWIDE's Avatar
    SGWORLDWIDE is offline Cadillac Owners Enthusiast
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    SES Light Fuel system lean codes?

    Hey guys thanks with the help on that iac valve seems to make her start up fast anyway anoher thing popped up now I started her today and the ses light came on pulled the codes and got these

    p0171 Fuel Trim System Lean Bank 1 CURRENT
    p0174 Fuel Trim System Lean Bank 2 CURRENT


    figure these are what are causing it as there current aswell what u guys think and what does it mean

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: SES Light Fuel system lean codes?

    Large vacuum leak - either the PCV dirty air line, intake manifold overpressure valve or intake manifold to throttlebody connector Plenum. Discussed endlessly - fixes in Tech Tips.

    The Deville, right ?? (This is the Deville forum, but both your (intended) cars can have the same problem)

  4. #3
    SGWORLDWIDE's Avatar
    SGWORLDWIDE is offline Cadillac Owners Enthusiast
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    Yup the deville will look into it

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: SES Light Fuel system lean codes?

    My money is on the plenum duct. Very common failure on the 2000+ motors.

  6. #5
    SGWORLDWIDE's Avatar
    SGWORLDWIDE is offline Cadillac Owners Enthusiast
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    Thanks ranger I'm going to check it out weird that after I cleaned the IAC valve now the ses light comes on and I got lean codes though start up feels much improved fires right up after u cleaned the IAC hopefully can find this problem

  7. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: SES Light Fuel system lean codes?

    When you check the plenum, be sure to flex it with your finger while spraying near the 6:00 position. Flexing it will open the rip if it's there allowing the spray to enter the intake and raise the RPM.

  8. #7
    SGWORLDWIDE's Avatar
    SGWORLDWIDE is offline Cadillac Owners Enthusiast
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    Okay got the problem figured out and fixed hopfullly first the o ring was missing on the IAC valve besides being dirty and second my mechanic found the intake manifold gaskets leaking causing the stalling rough start and idol high rpm and just lack of power while he was in there he changed the plenum duct as well 150 out the door parts and all

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