Jump to content

The RennTech.org community is Member supported!  Please consider an ANNUAL donation to help keep this site operating.
Click here to Donate

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

CEL not MAF, 1123, 1125, and 1551?!

Recommended Posts

I'm a total newbie. '99 Boxster 2.5, 5 speed, 71K miles. I've got a solid CEL with codes 1123, 1125, and 1551. Car runs and idles fine in my opinion. From what I read previously (which has been incredibly education BTW), I thought it might be a bad MAF. Removed and cleaned as prescribed, reset by disconnecting neg terminal on battery - CEL comes backafter 5 miles. So, I unplug the MAF connector, drive 25+ miles, NO CEL and it drives fine. I'm thinking, GREAT, just buy a new MAF and replace. I did this today, brand new MAF from Autohauz - drive 5 miles, CEL is back on.... :angry: I haven't had codes read yet, but what might you think could be the possible options based on the previous codes??? I'll be getting new codes, but wanted to put this out there... Thanks for any help!!

Link to comment
Share on other sites

  • Admin

P1123 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Lean Threshold

P1125 Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Lean Threshold

These codes mean that the DME can not adjust a too rich mixture (it has leaned the mixture as much as possible but can't correct it enough).

PI551 Idle Air Control Valve Closing Coil - Open Circuit

Potential causes:

- Break in wiring.

- IAC valve faulty.

- DME control module faulty

The Idle Air Control Valve sticking could cause a too rich condition that codes say they saw.

I would remove and clean the IAC and make sure it is moving freely. In a few cases the solenoid on the valve fails and it then needs to be replaced.

Link to comment
Share on other sites

Thanks Loren!

So, again, newbie here... On the image here, which is the IAC valve? I've not had to mess with such before and would I clean it with carb cleaner? Any general precautions to take or is it just a straightforward cleaning? Thanks again!


Link to comment
Share on other sites

  • Admin

Your diagram is the air injection circuit. IAC is not part of that.

The IAC (item 3) in on the throttle body.

Do not damage of lose the paper gasket item 16.


Yes, sometimes it helps to clean it with carb cleaner. The metal window inside should turn easily.

While you are there I would cleant he throttle body and throttle butterfly too - especially the backside of the throttle butterfly.

As I said in some cases the solenoid fails and the valve then needs to be replaced.

Link to comment
Share on other sites

Thanks again, Loren! You've been a huge help. I'll try it out!

BTW - I knew this site was good when I found the spoiler switch behind the fuse box as suggested here. Turns out, people kick it through frequently. I had NO idea what happened to it until I took the four screws out and looked behind. Small thing, but this place has it all.

Link to comment
Share on other sites

  • 4 months later...

Been a while, but I've cleaned the IACV and throttle body while I was at it. Seems to operate well, although I have codes 1514 and 1551 - all IACV. I don't have ANY issues with idle and all operates normally - very steady idle, no stalling, no problems with RPM's dropping significantly even with AC... other than the annoying CEL. Is there any reason to replace the IACV ($$) if the car runs perfectly well?? Could the codes relate peripherally to something other than a specific IACV issue?


Link to comment
Share on other sites

  • Admin

P1514 Idle Air Control Valve Opening Coil - Open Circuit

Possible causes:

- Break in wiring.

- IAC valve faulty.

- DME control module faulty

P1551 Idle Air Control Valve Closing Coil - Open Circuit

Possible causes:

- Break in wiring.

- lAC valve faulty.

- DME control module faulty

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.

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.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.