2005 Deville codes 0171 and 0174
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  • 2 Post By Suprdave1
  • 1 Post By Festus40
Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 2005 Deville codes 0171 and 0174 in Past Cadillac Vehicle Discussion; I have these 2 codes and it says lean bank 1 and lean bank 2....fuel pressure or MAF. I priced ...
  1. #1
    Suprdave1 is offline Cadillac Owners Member
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    2005 Deville codes 0171 and 0174

    I have these 2 codes and it says lean bank 1 and lean bank 2....fuel pressure or MAF. I priced a MAF sensor and at $250 or so I want to make sure that is the issue. How do I check fuel pressure or how would I tell if it is fuel pressure or the MAF sensor? The check engine light first showed a loose fuel cap which I tightened, cleared the code and then after a few days it came up with the 2 codes above.
    Thanks

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 2005 Deville codes 0171 and 0174



    It's neither. It is a rip in the plenum. That's the rubber coupler between the TB and the manifold. Replace it and your problem will be solved. You'll need to pull the manifold to replace it.

  4. #3
    Suprdave1 is offline Cadillac Owners Member
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    Re: 2005 Deville codes 0171 and 0174

    Any instructions on doing this? I tried searching

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    MoistCabbage's Avatar
    MoistCabbage is offline Cadillac Owners 10000+ Posts
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    Ranger's Avatar
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    Re: 2005 Deville codes 0171 and 0174

    Pretty straight forward. Depressurize the fuel rail. Disconnect it from the fuel supply line and remove it (with the injectors attached). Remove vacuum lines and throttle cables. Unbolt and remove the manifold (with the TB). Remove the TB & plenum from the manifold. Replace plenum and reverse the procedure.

    Check the Tech Tips section. There may be a tutorial in there.

    EDIT:
    Oops, MC beat me to it an found it.

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 2005 Deville codes 0171 and 0174

    Pictures of the plenum and manifold parts in my albums - click my username, open the profile, 2 albums, 6 pages of Northstar stuff in the lower left column.

    The intake manifold is dry - no coolant involved. You can probably re-use the 8 manifold seals. Manifold bolt torque is only 89 lb/in - less than 7.5 lb/ft. Be careful.

    A MAF sensor will set its own codes. Fuel pressure should be 40 - 44 psi at Key:ON, 41 - 47 psi running, measured at the test port on the fuel rail. With the engine OFF there should be NO gas in the FPR nipple or vacuum line.

    FWIW, RockAuto is selling the Dorman plenum and all 8 manifold seals for $15.10 + shipping. (A dealer gets $7 apiece for the silicone seals.)

    Look real hard at this crossover assembly - the throttlebody-plenum bolts are #17 - the "nuts" are welded to the plenum base - the TB bolts have to be loosened................

  8. #7
    PineyJustice is offline Cadillac Owners Fanatic
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    Re: 2005 Deville codes 0171 and 0174

    Spoiler, the bolts to take the plenum off are on the intake box and not the manifold side of the throttle body.

    The whole process is very easy, just go slow and don't lose anything, the intake manifold bolts are supposed to be something around 8 foot pounds, remember, the intake is a very strong plastic but still plastic, you just want those bolts snug or it will crack.

    Also this would be a good time to clean out the gunk from inside the manifold as well as get some new felpro gaskets for it, you have to take it off anyways at this point so it's real easy to do as well as cheap.

  9. #8
    Suprdave1 is offline Cadillac Owners Member
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    Re: 2005 Deville codes 0171 and 0174

    Just to update. Finally found time to do this. I removed the plenum and found the coupling was intact, but was beginning to dry rot. What I did find was the vacuum line on the end of the plenum was rotted through at the elbow! This was probably the culprit, but I'm not sure it could have been replaced without pulling the plenum anyway! I did go ahead and replace the coupling and cleaned the plenum and throttle body. Thanks for all the help and it was about a 2 hour job, but I had to go get the vacuum elbow.
    Dave

  10. #9
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 2005 Deville codes 0171 and 0174

    You removed the intake manifold, not the "plenum". The line into the passenger end of the manifold is the PCV dirty air line - it runs from the right (rear) cam cover into the tunnel in the passenger end of the intake manifold.

    The "plenum" is the rubber/metal coupling between the intake manifold and throttlebody. Post #6, Part #10.

    Picky, picky, I know - and "plenum", as used in this instance by GM, flies in the face of the King's English. "Plenum" more correctly describes the intake manifold.

  11. #10
    Suprdave1 is offline Cadillac Owners Member
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    Re: 2005 Deville codes 0171 and 0174

    OK, thanks..I fixed it anyway..LOL thanks for the help

  12. #11
    Festus40 is offline Cadillac Owners Member
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    Re: 2005 Deville codes 0171 and 0174

    Thanks to all that have posted to this website about this problem. I was helped by the step-by-step instructions and pictures of the removal and replacement of the intake. Had a real fit with the right-angle vac. adapter on the pass. side of the manifold. Should have hooked up line before installing intake, but recovered by finally paying my mechanic to hook it up. "My back couldn't take it any more" Long story short, replaced plenum and all o-rings with new. Cleaned mating surfaces with cleaner. Installed bolts with in/lb torque wrench using inside to outside pattern. Finally got everything back and found Schreider valve on fuel line stuck open. Replaced same. Result= No more codes..I will donate at least $50 to this site because it has been so helpful. Remember, it doesn't maintain itself...
    Domino1968 likes this.

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