Need Help With Boxster Codes

I hate to muddy the blog with service requests and general troubleshooting, but we’ve got such smart Porsche people reading the blog, I hate to waste the talent and resources.  Plus, this is for Joe who’s been a regular on the blog nearly since the beginning, so we’re helping one of our own.

Here’s a question Joe sent me today:

Check engine light came on the other day. Pulled up these codes on my Boxster: P1123 and P1125. Figured I would check with the experts at PorschePerfect if they had any idea. Some forums say sensors see a rich/lean mixture because the mass airflow sensor is sending a signal to the dme to go rich or lean.

Any help or insight anyone can provide Joe in the comments would be greatly appreciated by both him as well as me. Gotta get that Boxster in tip top shape so he can send us some more snow driving pictures like he did last year!

Thanks everyone!


  1. Thanks for posting this Ryan!

  2. 1123 – Oxygen Sensor

    1125 – Air Temperature Sensor

  3. P1123 – Oxygen Sensor Sensing Range 1 Cylinder 1-3

    P1125 – Oxygen Sensor Adaptation, Upper Load Range, Bank 1, Above Limit

  4. Thanks. Does that necessarily mean a bad O2 sensor?

  5. I did Not Hear About Boxster codes , But In My suggestion that you try something on Google Search about that

  6. Scan the code again and erase the code and restart the car and see if the check engine light comes on again. If not you’ll have to get the O2 sensor replaced.

  7. Joe, Find a Porsche specialist in you area and call. tell him whats wrong and see if he sounds like knows the problem. You don’t want to take the car to a mechanic who is going to start throwing very expensive darts.
    Make sure they have experience with your car. the porsche club should be able to help you find someone.

    • Laurence carpenter says

      I have a 1998 Porsche boxter. Under the seat a box m535unit I repalaced it we a used one same year as mine. All works but car won’t start. Where can get it looked at

  8. Joe, Sorry my comment didn’t come out the way I meant. I have a code reader and my wifes Jetta came up with an O2 code so of coarse
    I replaced the O2 sensor. didn’t work so off to the mechanic they said it was the air mass meter for $600. Turned out that wasn’t it, I don’t remember what the next thing they said that it must be but I do remember that it was $1000. this was a car that the engine was easy to access. I know that in the Boxster there are jobs that require the engine to come out, couple that with expensive part prices and guessing at whats wrong can get pricey.

  9. Update (in case anyone cares): Codes have been cleared. Waiting to see if they come back on again. Crossing fingers…

  10. I have 99 porsche boxster change the first and second oxygen sensors now it the catalytic converters reading and the check engine light go on and off not blinking but runs fine i use 87 octane unleaded gas. could the codes say cats but mean oxygen sensors?SHOULD I CHANGE THE OTHER 2 SENSORS? AND IF IT IS THE CATS WHAT BRAND DO YOU RECOMMEND BECAUSE MY BOXSTER HAS 161000 PLUS MILES? I DONT THINK PUTTING BRAND NEW PORSCHE FACTORY CATS ON A OLDER PORSCHE BOXSTER? THANKS FOR YOUR TIME RICH