Help with PC0174 code
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 6 of 6
Northstar Engines and System Technical Discussion Discussion, Help with PC0174 code in Cadillac Engine Technical Discussion; Hello, I purchased a 1996 Seville SLS about 7 months ago. With the exception of a rough idle only when ...
  1. #1
    bobc327 is offline Cadillac Owners Member
    Automobile(s): 2003 Seville STS
    Join Date
    Nov 2004
    Location
    Plymouth Meeting, PA
    Posts
    2

    Help with PC0174 code

    Hello,

    I purchased a 1996 Seville SLS about 7 months ago. With the exception of a rough idle only when you first start it up it ran fine until about 2 months ago when it would not start. Turned out to be the positive battery cable that was badly corroded. Took it to the dealer and had the positive cable replaced, coolant flushed/changed and had the fuel rail replaced under the recall. Since then I have been getting a PC0174 code about twice a week and lately it seems even more frequently. I have also noticed it seems to idle very low, about 250 rpms (can't remember what it was before taking to dealer). I have the analog guage where it is at the first mark. When it is warm and I am in drive with my foot on the brake, it idles at about 200 rpm and the oil light occasionally will flicker. I have read in other posts where I think it should be about 450 to 500 rpms.
    I have replaced the air filter, pvc value and cleaned the throttle body real good. I purchased the car from a small used car dealer that told me he had his mechanic replace the plugs and plug wires. I can not tell what brand the wires are, but the plugs are Autolite double platinums. After reading other posts on this board where you should only use AC Delco plugs and wires and that the wires can be damaged by the dealer after the fuel rail recall (thats probably if they are older), I have order a set of AC Delco wires and plugs.
    Hopefully, they will be deliver by the weekend so I can put them on.

    I looked up code PC0174 (Fuel Trim System Lean Bank 2) but do not know what to check for, or what needs to be replaced. I know I should probably take it back to the dealer, but I am afraid they will charge me a fortune that I don't have right now.

    Any help would be greatly appreciated.

    Thanks
    Bob

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    bobc327 is offline Cadillac Owners Member
    Automobile(s): 2003 Seville STS
    Join Date
    Nov 2004
    Location
    Plymouth Meeting, PA
    Posts
    2

    Re: Help with PC0174 code

    Hello,

    I replaced the plugs and wires yesterday with the correct AC Delco parts (plugs 41950 and wires 748J). Took the car for a ride last night and this morning and both times the PC0174 code appears again. I did not notice any difference in smoothness or performance with the new plugs and wires. The idle did not change and still seems to be low, about 250 rpms on the tach. After I replaced the plugs and wires I removed the negative battery cable for 30 minutes incase something needed to be reset.
    Could the low idle be a bad ISC unit? I found another post where you can check the operation of the closed throttle switch with the onboard diagnostics. In the PCM mode the LO icon should be on if things are Ok. On mine the LO icon was not on, but the post was referring to a wandering and high idle. Since my problem is a low idle, I am not sure if a new ISC unit would fix the problem.

    I founded some info on the internet that a PC0174 code can be cause by a dirty or faulty MAF sensor or a vacuum leak downstream from the MAF sensor. I checked for vacuum leaks but could find none.
    Does anyone know how to check if the MAF sensor is bad? To clean it, should I just spray the sensor with the same stuff used to clean the throtle body or is there a special procedure to clean the MAF sensor?

    I hate to just start replacing parts without knowing for sure they are bad.
    Any help would really be appreciated.

    Thanks
    Bob

  4. #3
    phathead785's Avatar
    phathead785 is offline Cadillac Owners Fanatic
    Automobile(s): 1996 Cadillac Deville, 2004 Cadillac DTS, 2011 CTS AWD Coupe
    Join Date
    Aug 2005
    Location
    Boston MA
    Age
    26
    Posts
    328

    Re: Help with PC0174 code

    I'm having the same issue with my 96 Deville. Anyone know how to fix it?

  5. #4
    tco43 is offline Cadillac Owners Member
    Join Date
    Jan 2004
    Posts
    81

    Re: Help with PC0174 code

    I read somewhere (I think in the Seville/Eldo forum) that one source for the P0171 and P0174 codes is either a disconnected or leaking/cracked vacuum hose. I think a good start is to do a thorough check of all the hosing.
    I cleaned the EGR and throttle body on a 2002 STS and it started throwing those two codes. I haven't gotten back to it yet, so don't know if I left one off or what.
    Let us know.

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    73,267

    Re: Help with PC0174 code

    Yeah, look for a vacuum leak.

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
    Automobile(s): 2002.5 F55 STS/65500mi, 2004 Ford F150 SuperCab4x4
    Join Date
    Feb 2006
    Location
    MD Eastern Shore - Kent Island
    Age
    74
    Posts
    44,513

    Re: Help with PC0174 code

    Don't spray anything on or in the MAF. In the '02 FSM P0174 sets due to fuel system lean/rich trim attempts. My guess is that, coupled with the low idle speed (600-650 spec), something is very dirty in and around the throttlebody and IAC system (Idle Air Control)

    Surf around in here and do a search (top of page) for throttlebody cleaning and IAC cleaning. Don't use choke cleaner per the FSM.

    Also find the thread concerning using Google to search inside these forums. There are differences between '96 and '02, so use this as a guideline, OK?

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting