I cannot go above 4000 RPM,
and Durametric shows faults P1120 and P1121.

3 months or so ago, the throtle body EDIT: AND MAF WERE cleaned.
Now the problem is back. I don't use Ethanol.

Does anyone know why this keeps happening?

 

thats wierd - its e-gas right?
maybe something to do with that... I really dont have any idea, does it run smooth?

 

After cooling down it worked fine for a 20 Km, then it lost power again.
I just did the same trip back home, 40 Km, and it worked fine.

Durametric still shows the error codes, and I am thinking of not erasing them until
a tech takes a look at it.

Dayum it sucks to loose power suddenly... the last time it happened, today at around 4:30 pM or so,
it was at WOT at around 5500 RPM, and it was as if someone touched the breaks,
suddenly reducing it to 4000 RPM, as I was about to shift from 2nd to 3rd gear. F###K!!

 

P1121 - Oxygen sensor heating 2 ahead of converter - below lower limit.

The O2 sensor on bank 2 ahead of converter not getting hot enough and it is a heated sensor, so the fault can in the sensor and its heating element.

Possible causes: contact resistance high (bad connection due to corrosion or...); heating resistance too high; interruption of heating circuits; interruption in the sensor signal wire; short circuit to plus (power?).

I do not know if it is possible with the 996 engine and its sensors -- you have to determine this -- but one "trick" is to swap the #1 and #2 sensors. That is move the sensor from ahead of the converter to behind the converter and move the sensor from behind the converter to ahead of the converter.

The sensors must be disconnected from the wiring harness then carefully unscrewed from the exhaust piping and just as carefully and correctly installed and reconnected in their new location.

Again though this assumes the sensors are interchangeable. They are with my 02 Boxster. They may not be with all MY Boxsters or Caymans or in your case your 996's engine.

If the faults remains associated with the rear sensors the problem is the wiring to the sensor connectors. If the fault does not reappear or appears as P1117 or P1118 then one or both of the sensors original located behind the converters bad. I'd advise replacing sensors in pairs if you decide one sensor bad and in need of replacing.

There are other electrical tests. I can post details or better yet supply an email address and I'll send a copy of the tests -- a page and half -- in PDF format to you.

Sincerely,

Macster.

 

Pre and post cat sensors are different on a 996. What year is your car?

 

Macster
Thank you for your reply with helpful info.

There are a few questions you may know the answer:

1. Back in 2006 I switched the original headers to 997 (S?) heathers; my car is a 996 2002 C4S.
Could these heathers be part of some of the damage done to the ahead converter sensors?

2. would you advise to go back to original heathers?

3. I also have, what many refer here to as Mark 2 exhaust mod to original muffler,
which is a J pipe connected from the input to the output of of the muffler.

Could this modify wave dynamics in the collector and other pre-converters points,
causing temperature abnormalities and damaging the sensors?

4. Would cleaning the sensors (like I cleaned the MAF with MAF cleaner) work?

Yes, I would appreciate if you send me the PDF you mentioned. My email is jjstudio@rogers.com

5. Where is the best place to get the sensors, and is it a simple DY job?

Thanks
John

 

Hi Dharn, it is a 2002 996 C4S.

Interestingly enough, I don't see any other threads with these two codes
together ( P1120 and P 1121).

Why only me?

PS I read your thread on replacing your cracked cylinder head- impressive for a civilian... or are you a mechanic?

 

One more thing:

Macster, Durametric says
P1120 is Throtle Plate
and P1121 is Throtle position sensor.

It says nothing about ahead converter sensors.

Is there a chance you may have somehow read the wrong code info?

 

I drove for several hours last evening, and car pulls strong.
I did not yet clear the codes with Durametric.

So, whatever the problem is, it is intermittent- worst kind for techs to troubleshoot.

 

Any other ideas or wise words?

 

Something I said?

 

probably site's been down last couple of days and most members have stayed away till the problem is solved. hang in there

btw what is a heather...is she cute?

 

Cats. When they fail they plug up. They flow more when cold, then as the ceramic element heats up they restrict flow. Happened to me twice on different cars....

 

...you can use it to measure temps on either element of the cat. Get the High-temp version of the IR thermometer - one that goes up to 1500 deg or so. They have a laser aiming device so its easy to pinpoint areas to detect subtle or drastic temp changes. The high temp side should be the clogged side. I had this happen on one of my 993's.

 

aah! I knew it was something I had said! yep, she has voluptuous curves, and loves to collect and exhaust.