Lean codes. Where to start?
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  • 1 Post By redoxy
Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Lean codes. Where to start? in Past Cadillac Vehicle Discussion; In the last 4 weeks Ive noticed that my car has a slightly rough idle. its not something I can ...
  1. #1
    13ir14314's Avatar
    13ir14314 is offline Cadillac Owners Fanatic
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    Lean codes. Where to start?

    In the last 4 weeks Ive noticed that my car has a slightly rough idle. its not something I can see on the tach but could hear it. I thought it just needed a TB cleaning and let it go until I can do it. Now last night the car lit the MIL and gave 0171 and 0174 lean bank 1,2. the first thing that I can think is the plenum is cracked but I don't have any cleaner right now to check it. Is there something else that will cause these codes and that I can check? Should I just order a plenum so I have it if it is bad?

    Also when checking codes I found P1617 oil lever circuit as a history code. Ive never have the low oil light come on. What would cause this code?


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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Lean codes. Where to start?

    P 0171 and P 0174 usually indicate vacuum leaks - assuming this is in the 2002 DHS, you might start with the clamps and flex ducting for the air intake and MAF - any air leak there will set codes. Remove the engine cover and check the PCV dirty air line - from the right (rear) cam cover to the tunnel in the front (passenger end) of the intake manifold - a crack or disconnect here would be a big vacuum leak. Your intake manifold overpressure valve is a different design from earlier, and it's under the plenum anyway. (Pictures in my albums).

    P 1617 might (not usual) have been caused by road water splash - shorted wiring or connector. Check the wiring.

    Invest in a mechanic's stethoscope from a NAPA store. Perfect for snooping for hissssssesssss.

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Lean codes. Where to start?

    A ripped plenum duct is almost a sure bet

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    13ir14314's Avatar
    13ir14314 is offline Cadillac Owners Fanatic
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    Re: Lean codes. Where to start?

    I want to order a new plenum and intake gaskets just encase that is there problem. Looking on Rock Auto they only have Doorman. I know this is usually what O'reillys sells, so is it something I can trust or is it cheap rubber? Should I look else where for GM or Fel-Pro?

  7. #5
    redoxy is offline Cadillac Owners Fanatic
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    Re: Lean codes. Where to start?

    Quote Originally Posted by 13ir14314 View Post
    I want to order a new plenum and intake gaskets just encase that is there problem. Looking on Rock Auto they only have Doorman. I know this is usually what O'reillys sells, so is it something I can trust or is it cheap rubber? Should I look else where for GM or Fel-Pro?
    I bought the same product from rock auto and so far no issues. It has been over 1.5 years since I installed it. Also the dorman plenum duct comes with the intake manifold gaskets.
    13ir14314 likes this.

  8. #6
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Lean codes. Where to start?

    Dorman products are usually pretty good.

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