25 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHLoss of power, no rev above 4500RPM, and fault codes P1120 and P1121
Reported or suspected cause
back
Reported cause
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0
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Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
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Leading evidence: 'back' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'back' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Clean mass air flow sensor' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
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.
Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
wiring
Suggestion or failed attempt
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Identified cause
1
Suspected cause
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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suspected cause
If the faults remains associated with the rear sensors the problem is the wiring to the sensor connectors.
Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
Clean mass air flow sensor
Suggestion or failed attempt
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0
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Unsuccessful attempts
1
Discussions
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Suggestion · Original poster
Would cleaning the sensors (like I cleaned the MAF with MAF cleaner) work?
Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
Clean sensors (like i
Suggestion or failed attempt
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0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
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Suggestion · Original poster
Would cleaning the sensors (like I cleaned the MAF with MAF cleaner) work?
Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
Disconnect from the wiring harness
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Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed
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.
Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
Replace meaning of the p1120/p1121 codes
No successful repair reported for this finding.
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Suggestion
If you have a newer model car with a different and newer engine controller firmware image it is possible Porsche changed the meaning of the P1120/P1121 codes.
Loss of power, no rev above 4500RPM, and fault codes P1120 and P1121
Coverage and how to read this overview
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
25 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
3 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
After cooling down it worked fine for a 20 Km, then it lost power again.
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?
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.
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
[email removed]
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.
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.
Mine would be normal until they heated up then restrict the motor to 5k or so. If they overheated and melted, the ceramic element would become brittle and could be moving around inside. I'd keep driving if it's OK, see what happens...
It is possible. My info is for Porsches from 1996 to 2004. If you have a newer model car with a different and newer engine controller firmware image it is possible Porsche changed the meaning of the P1120/P1121 codes. All P1XXX codes are manufacturer specific and the manufacturer is free to change these whenever it wants to.
I find it hard to understand why if the codes are related to the O2 sensors why the engine would not run above 4500 rpms. This sort of sounds like it is throttle related. However, e-Gas malfunctions generally result in the e-Gas being confined to limp home mode and engine speed limited to less than 4500 rpms.
If the codes do reflect a problem with the O2 sensors it could be -- and I write this with just a glance at some other posts -- something in the exhaust downstream of the O2 sensors that is playing havoc with exhaust gas flow. If the exhaust gas doesn't flow the O2 sensors may not stay hot enough and the error codes are the result.
Would I advise you to go back to the stock exhaust? No, not without more evidence the exisiting exhaust system is the problem.
Sincerely,
Macster.
If you want more help you gotta post pics of Heather first.
Seriously, I'll get the info I promised off to you Monday. As someone else mentioned site's been down for several days.
Sincerely,
Macster.
Macster, as I mentioned earlier, it is a 2002 C4S.
The last 2 days, it is working perfectly well. However it makes me nervous to
know it may be back; imagine to loose power suddenly, and be forced down from 6500 RPM to 4500 RPM, just as I needed it to get out of a trucks path,
or any similar passing maneuver- not good!
I hope it was.
I think this thread went out into left field with a O2 sensor red herring.
I am having throttle gremlins with some constant and some intermittent codes:
(a 2003 C4S read by a Durametric) The throttle body was replaced with a Bosch unit 2 years /14k mi ago (P.O.)
Fault codes 07062023
08:00
P1120
Porsche fault code 117 - Throttle plate
P1122
Porsche fault code 431 - Throttle potentiometer 2
P1121
Porsche fault code 430 - Throttle position sensor 1
11:00 After a drive (and not developing full power above 3000 rpm...)
P1120
Porsche fault code 117 - Throttle plate
P1122
Porsche fault code 431 - Throttle potentiometer 2
P1138
Porsche fault code 430 - Throttle position sensor 1
P1514
Porsche fault code 540 - Throttle adjuster Lower mechanical stop
At 14:30
P1514
Porsche fault code 540 - Throttle adjuster Lower mechanical stop
P1120
Porsche fault code 117 - Throttle plate
P1138
Porsche fault code 430 - Throttle position sensor 1
I am looking for the Throttle Pedal Sensor: 996 606 115 00 to .02
(first searches NLA. From secondary suppliers:appx $1000)
I also looked up the Bosch number (on the unit) no joy.
Paul
This is a source reference. Confirm exact model applicability in the original material.
