Jump to content
CaddyInfo Cadillac Forum

pc171 and pc174

Recommended Posts

I have a 96 sts and the engine light came on. The codes i'm getting are pc171 and pc174 fuel trim lean bank one and two. at first i was only getting pc174 and the engine light would go off after a couple of times driving the car. then it would come back on. lately I'm getting both pc171 and pc174 but the engine light still comes and goes. The car seems to run fine, no cold start problems but it is harder to start when warm after driving. any ideas on what to look for? i've read a couple of posts on the subject with newer models, would the same info apply to the 96? also the fuel gage doesn't work right. It only shows its true level when you start the car. You can drive 150 miles and the gage doesn't move untill you restart the car. It appears to be accurate according to the dic info. when i refill the tank it takes pretty close to the amount the dic says it used. any ideas

Edited by pas96
Link to comment
Share on other sites


I've always found the fuel gauge to seem a bit sticky. Accurate when you start up, as you say, but not prone to moving much during a drive. On long drives it will move, though.

The most likely thing to cause the PC171 and PC174 are vacuum leaks. As Ranger says, you can check the gaskets on the intake manifold and throttle body; I think that there is an O-ring on the throttle body assembly somewhere. Other sources of vacuum leaks are a PCV valve stuck open, a broken or cracked vacuum hose, the oil filler cap loose or off, or the dipstick not all the way down or missing. The FSM also says that a clogged air cleaner element can cause lean codes.

-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...