I need to figure out this lean thing - P0171
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1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, I need to figure out this lean thing - P0171 in Past Cadillac Vehicle Discussion; Ok so some of you may remember I was having a problem with an O2 sensor. That got replaced today. ...
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    codewize's Avatar
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    I need to figure out this lean thing - P0171

    Ok so some of you may remember I was having a problem with an O2 sensor. That got replaced today.

    Now what I have is P0171 - Fuel Trim System Lean Bank 1. As soon as I clear it, it comes back. A few times I got a few minutes out of it before the code reappeared but for the most part it comes right back.

    What should I be looking at here? Intake plenum, intake manifold. It's always bank 1 so I don't think it would be in the plenum or the runner from the air box. It would almost have to be the manifold, right?

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    Re: I need to figure out this lean thing - P0171

    What year? I'd start by looking for a vacuum leak on that side first.

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    codewize's Avatar
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    Re: I need to figure out this lean thing - P0171

    This is the 01 DTS. I looked at all the lines going to the AIR pump, I looked at other hoses and such and I don't see anything funky.

    I also tried to spray that side of the intake but I used carb cleaner rather than starter fluid. Probably not the same effect huh.

    Kind of odd. I dind't take the car out yet today but I did let it idle for a bit with no codes.
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    Ranger's Avatar
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    Re: I need to figure out this lean thing - P0171

    Carb cleaner should work just as well. Did you spray around the infamous plenum?

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    Re: I need to figure out this lean thing - P0171

    OK so, today I drove for probably 30 - 40 miles. No codes. Then on the way home I got P0131 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 1. I cleared that and it stayed away.

    So I guess replacing the $80 sensor did nothing for me.

    What do you guys think.

    I did not spray around the plenum, I can't believe that all the codes would be on bank 1 if it was something that far up in the air stream.

    Let me ask this and correct me if I'm wrong. Bank 1 sensor 1 is the sensor in the rear bank manifold, correct? Rear bank being closest to the firewall. This is really driving me crazy now and it's starting to cost money.
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    Re: I need to figure out this lean thing - P0171

    you tell me which code youd like to know about and ill post everything ESI says on it haha

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    Re: I need to figure out this lean thing - P0171

    Let me ask this and correct me if I'm wrong. Bank 1 sensor 1 is the sensor in the rear bank manifold, correct? Rear bank being closest to the firewall.
    Correct. I agree with your thinking about the plenum, but I'd check it to rule it out anyway. Otherwise it remains an unknown and a possibility.

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    Re: I need to figure out this lean thing - P0171

    I'll check it tomorrow. I'm good with that logic. I'll also recheck the intake as I didn't go crazy because I was using cleaner and not starting fluid, so I didn't know what the result could / would be so I didn't go crazy.

    STS; I want to know about both of the codes I'm getting. P0171 and P0131

    Quote Originally Posted by Ranger View Post
    Correct. I agree with your thinking about the plenum, but I'd check it to rule it out anyway. Otherwise it remains an unknown and a possibility.
    Ownership:
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    2011 CTS4 Luxury

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    Re: I need to figure out this lean thing - P0171

    Shes going in on Wed to be looked over
    Ownership:
    91 Brougham d'Elegance 350
    95 Fleetwood Brougham
    01 Custom Deville DTS
    2011 CTS4 Luxury

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    Re: I need to figure out this lean thing - P0171

    Hi everyone.. im new here so just bear with me,but im getting those same codes plus P0101 and P0174..Also has service emissions system and check engine light on..I have a 96 concours with 122000 miles...

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    Re: I need to figure out this lean thing - P0171

    Check for vacuum leaks.

  14. #12
    codewize's Avatar
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    Re: I need to figure out this lean thing - P0171

    I may or may not have mentioned that I cancelled my Wed appt that week because the codes were gone and I couldn't make them come back.

    At this point it's very intermittent. Some days I get codes and some days I don't
    Ownership:
    91 Brougham d'Elegance 350
    95 Fleetwood Brougham
    01 Custom Deville DTS
    2011 CTS4 Luxury

    Memberships:
    National and regional Cadillac & LaSalle Club
    Proud Volunteer - Northstar Tuning Project
    Guinness World Records - Largest Cadillac Parade

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