CEL - p0139 and p1117 First time so I will probably clear and monitor. That said, it looks like the codes suggest a bad O2 sensor. Is there more to it than that?https://pedrosboard.com/read.php?7,30070,30070#msg-30070Mon, 10 Aug 2026 00:37:41 -0400 Phorum 5.2.23 https://pedrosboard.com/read.php?7,30070,57291#msg-57291 I just ordered the BOSCH branded parts from the "jungle website"https://pedrosboard.com/read.php?7,30070,57291#msg-57291One pigtail looks substantially shorter in the pictures. We will see.

In any event, they were $50 each. Which I submit is a pretty decent price all things considered.
My car has 96K miles on it as do the original O2 sensors. I will be under there anyway and they are all pretty close to EOL. In my mind (FWIW), it makes sense to swap all four and thus keep them all matched.

I deferred this repair for almost 13 years, by basically ignoring the problem. So, it is really OK to finally fix it.

To be clear, I have not done anything to date other than clear the codes a couple times. The earlier clearances stayed fine for years at a time.
Now, they are re-triggering the CEL within a couple weeks each time. It is time to make an actual repair and maintain the car properly.]]> JM-Stamford,CT Main ForumSat, 04 Oct 2025 12:14:47 -0400 https://pedrosboard.com/read.php?7,30070,57277#msg-57277 If you have high mileage on the pre-cat sensorshttps://pedrosboard.com/read.php?7,30070,57277#msg-57277
If the car has post-cat codes then I would move the best ones you have (they should be all interchangeable) to post-cat positions and put fresh ones in the pre-cat positions.

But that's just me. It's all about priorities.]]> Boxsterra Main ForumTue, 19 Aug 2025 15:06:19 -0400 https://pedrosboard.com/read.php?7,30070,57274#msg-57274 Just for fun the codes have come back for the first time since 2019....https://pedrosboard.com/read.php?7,30070,57274#msg-57274
I am beginning to think there was a random wiring issue. but who the heck knows?

This time, I cleared the codes and the codes came becak within a week. So I am becoming convinced that THIS time, the sensors really do need to be replaced.
Plus, it is time to do a ton of deferred maintenance anyway.

Just amazing how the codes flag stuff - that is just not a thing in real life.

Go figure.]]> JM-Stamford,CT Main ForumSun, 17 Aug 2025 15:42:28 -0400 https://pedrosboard.com/read.php?7,30070,51647#msg-51647 Could be an exhaust leak before the O2 sensorhttps://pedrosboard.com/read.php?7,30070,51647#msg-51647
Have you had the headers off? It's also possible (but unlikely) that the O2 sensor was damaged during installation. You can swap sensors to see if the problem moves.

FWIW, both of those codes point to the same O2 sensor (passenger side, before O2 sensor) so you can focus on that area.]]> Boxsterra Main ForumThu, 13 Jun 2019 07:05:16 -0400 https://pedrosboard.com/read.php?7,30070,51644#msg-51644 I normally would get codes 1275 and 0133 together.https://pedrosboard.com/read.php?7,30070,51644#msg-51644
Tony]]> Tony in Whittier Main ForumWed, 12 Jun 2019 21:39:01 -0400 https://pedrosboard.com/read.php?7,30070,51633#msg-51633 Specifically what codes? *NM*https://pedrosboard.com/read.php?7,30070,51633#msg-51633 Boxsterra Main ForumWed, 12 Jun 2019 06:15:40 -0400 https://pedrosboard.com/read.php?7,30070,51632#msg-51632 I am having a similar issue...https://pedrosboard.com/read.php?7,30070,51632#msg-51632 Tony in Whittier Main ForumTue, 11 Jun 2019 12:06:08 -0400 https://pedrosboard.com/read.php?7,30070,51628#msg-51628 Five years on ... Still have not changed the O2 sensor - code is back first time in 3 years....https://pedrosboard.com/read.php?7,30070,51628#msg-51628
I am going to do the same as I have done before - clear the code and wait. I am thinking this is an intermittent electrical gremlin and the sensor is just fine. But only one way to find out....

On a more depressing note - this thread demonstrates that I only put 22K miles on the car in around 5 years. In fairness, there was a two year loss of usage due to injury. But still, 6-8K a year is not enough.
The car is now my mostly daily driver. Exception for snow/salt condition. It is harder on the car because my commute is only 5 miles - barely enough time to warm water much less oil.
I make a point to drive a distance at least once per month. Put 150 miles just today.
But sheesh.....]]> JM-Stamford,CT Main ForumMon, 10 Jun 2019 21:41:21 -0400 https://pedrosboard.com/read.php?7,30070,40622#msg-40622 No. It simply suggests the fault is not a solid fault and after enough engine start/warm up cycles..https://pedrosboard.com/read.php?7,30070,40622#msg-40622
Quote
JMstamford,ct
Is that suggestive of a wiring problem rather than a sensor problem?

with the error condition absent the light is cleared and the error code is erased. I had this happen a few times with the converter fault I put up with for a couple of years. It might have cleared itself more often but almost every time I read the code and cleared the error so the DME didn't have time to clear it on its own.]]> MarcW Main ForumSun, 14 Jun 2015 16:07:29 -0400 https://pedrosboard.com/read.php?7,30070,40621#msg-40621 I hate intermittent faults.... *NM*https://pedrosboard.com/read.php?7,30070,40621#msg-40621 JM-Stamford,CT Main ForumSun, 14 Jun 2015 14:42:48 -0400 https://pedrosboard.com/read.php?7,30070,40620#msg-40620 This time, the light went out of its own accord. I did nothing.https://pedrosboard.com/read.php?7,30070,40620#msg-40620 JM-Stamford,CT Main ForumSun, 14 Jun 2015 14:42:15 -0400 https://pedrosboard.com/read.php?7,30070,40587#msg-40587 must be one heck of a common problem....https://pedrosboard.com/read.php?7,30070,40587#msg-40587 JM-Stamford,CT Main ForumThu, 11 Jun 2015 19:56:28 -0400 https://pedrosboard.com/read.php?7,30070,40580#msg-40580 That's a heck of a lot of views above X( *NM*https://pedrosboard.com/read.php?7,30070,40580#msg-40580 Gary in SoFL Main ForumThu, 11 Jun 2015 12:52:05 -0400 https://pedrosboard.com/read.php?7,30070,40579#msg-40579 Re: Sorry for the bump... But P1117 just came back - 2yrs later.https://pedrosboard.com/read.php?7,30070,40579#msg-40579
Quote
JMstamford,ct
As reported last time, I cleared the code and drove. I wanted to see if the car just threw a random code. I have since passed inspection etc. I have not been using the car very heavily due to a (now resolved) hip replacement. But it has been at least a few thousand miles and about a year and a half.

The return of the code is certainly suggestive that the sensor is, indeed failing. But apparently it is dying a VERY slow death. I am going to do the same as last time. Clear the code and see what happens.

If the code returns again, I will have to replace the sensor and I will likely replace both sides at the same time. I have seen it written that changing both is not necessary, but I am less than convinced.

O2 sensors can take some time to "die" or they can "die" right away, well, that is after some miles.

My previous experience with what proved to be bad sensors, at least one sensor, was the sensor failure was intermittent.

I wanted to catch the thing in the act but it took a while before I had a good sense of when it was going to fail to finally have at hand the OBD2 code reader/data viewer and could observe the sensor voltage values. The values were wrong but not as wrong as I had hoped. It was clear from the readings why the CEL took so long to appear. The sensor was working, just not very well.

More recently on the return leg of a trip I took to the midwest last Dec./Jan. my 996 generated an O2 sensor error, I forget the number now, but it pointed to the heating element of a sensor. I cleared the code at the station - a Shell station in Barstow, CA (might mention this was after having driven from Joplin MO over the span of 2 days or so) -- then drove on. I stopped someplace on I-5 and the CEL came on upon engine start after fueling. Same error code. I cleared it and drove on. Another stop for fuel and another CEL and the same code.

The failure was quite solid. At around 132K miles on the original sensors I just had all 4 replaced. A day's shakedown and I had the car in for its smog check which it passed with flying colors. The CEL has been dark ever since. As a bonus in this case -- but not the previous times I have replaced sensors in my Boxster -- the engine perked up some after the sensor change out.

It is up to you. You can continue to drive the car and put up with the intermittent CEL and sensor error code or you can have the indicated sensor replaced, and at 60K miles I would argue its counterpart on the other side should be replaced too.

I would lean towards the latter. For, ahhh, science I continued to drive my Boxster with a bad (though intermittently so) sensor but with the 996 science was involved. As soon as I could get the car in for new sensors I did so. Sure, I was under pressure to get the car smog checked -- it was past due -- but I would have had these replaced right away anyway.

And in the future if the Boxster sensors indicate a problem I'm just going to have the sensors replaced.]]> MarcW Main ForumThu, 11 Jun 2015 10:47:12 -0400 https://pedrosboard.com/read.php?7,30070,40575#msg-40575 Sorry for the bump... But P1117 just came back - 2yrs later.https://pedrosboard.com/read.php?7,30070,40575#msg-40575
The return of the code is certainly suggestive that the sensor is, indeed failing. But apparently it is dying a VERY slow death. I am going to do the same as last time. Clear the code and see what happens.

If the code returns again, I will have to replace the sensor and I will likely replace both sides at the same time. I have seen it written that changing both is not necessary, but I am less than convinced.]]> JM-Stamford,CT Main ForumThu, 11 Jun 2015 10:27:17 -0400 https://pedrosboard.com/read.php?7,30070,30226#msg-30226 Yes, and that meanshttps://pedrosboard.com/read.php?7,30070,30226#msg-30226 Boxsterra Main ForumThu, 26 Sep 2013 00:53:49 -0400 https://pedrosboard.com/read.php?7,30070,30209#msg-30209 Thanks *NM*https://pedrosboard.com/read.php?7,30070,30209#msg-30209 JM-Stamford,CT Main ForumWed, 25 Sep 2013 13:41:13 -0400 https://pedrosboard.com/read.php?7,30070,30208#msg-30208 $100 is a problem if it doesn't fix the issue. Then it is just a waste.https://pedrosboard.com/read.php?7,30070,30208#msg-30208 JM-Stamford,CT Main ForumWed, 25 Sep 2013 13:40:53 -0400 https://pedrosboard.com/read.php?7,30070,30168#msg-30168 Yes, there were different lengths and part numbers.https://pedrosboard.com/read.php?7,30070,30168#msg-30168this]]> mikefocke, '01S Sanford, NC Main ForumTue, 24 Sep 2013 15:36:04 -0400 https://pedrosboard.com/read.php?7,30070,30148#msg-30148 Well, I can't explain it. I recall swapping the front and rear and while they ...https://pedrosboard.com/read.php?7,30070,30148#msg-30148
'bout all I think of is Porsche changed the part numbers, elected to use sensors with the longer leads at all 4 corners to eliminate the sensors with the shorter leads to cut down on parts inventory.]]> MarcW Main ForumTue, 24 Sep 2013 04:39:33 -0400 https://pedrosboard.com/read.php?7,30070,30142#msg-30142 Same part # for all 4 from Porsche (even for 2002)https://pedrosboard.com/read.php?7,30070,30142#msg-30142
Part # 986.606.126.00 (2.5 1997)
Part # 986.606.126.01 (2.5 1998-1999)
Part # 986.606.126.01 (2.7/3.4 2000-2002)
Part # 986.606.226.00 (2.7/3.4 2003-2004)]]> Boxsterra Main ForumMon, 23 Sep 2013 20:58:03 -0400 https://pedrosboard.com/read.php?7,30070,30131#msg-30131 Come on. $100 (make that $200 or even $400) worth of parts is a problem?...https://pedrosboard.com/read.php?7,30070,30131#msg-30131
Quote
JMstamford,ct
I have been running since Thurs with the cleared codes. Nothing.

It might be that the IM readiness stuff is still playing out, but whatever it is, it is not condition critical.

But I want to be clear, these codes are suggestive of O2 problems and nothing else? The sensors are clearly the most obviousl thing, but since they are like $100, I don't want to be just throwing parts at a problem.

Well, then pay $150/hour for a diagnosis and then pay for the sensors.

In one of my sources for P0139 -- O2 sensor value does not change between rich or lean -- the only cause listed is "oxygen sensor".

Diagnostic conditions:
RPMs betwen 720 aNd 2400.
Engine load between 0.8 and 2.6 ms.
O2 sensor heating active.
Oxygen sensing ahead of the converter active.
Calculated converter temperature above 665F.
No fuel tank ventilation.
No faults detected for fuel tank ventilation and secondary air injection system.

Test: Road test vehicle. Erase DTC memory.

Heat the O2 sensors (road test vehicle under load), run the engine at high RPM with no load).

Perform short test during the diagnostic conditions can be reached.

Read DTC memory.

You can of course elect to continue to drive the car until such time as you are convinced it is the sensors or someone points you to another possible explanation. I'd offer one but my sources do not offer anything else.

Check that: With the P1117 DTC, possible causes are: contact resistance, heating resistance too high, interruption in the heating circuits, interruption in the sensor signal wire, short circuit to plus. There are some electrical tests but they all involve testing the sensor and its circuits and connector.]]> MarcW Main ForumMon, 23 Sep 2013 16:24:12 -0400 https://pedrosboard.com/read.php?7,30070,30127#msg-30127 Re: CEL - p0139 and p1117https://pedrosboard.com/read.php?7,30070,30127#msg-30127
It might be that the IM readiness stuff is still playing out, but whatever it is, it is not condition critical.

But I want to be clear, these codes are suggestive of O2 problems and nothing else? The sensors are clearly the most obviousl thing, but since they are like $100, I don't want to be just throwing parts at a problem.]]> JM-Stamford,CT Main ForumMon, 23 Sep 2013 11:49:13 -0400 https://pedrosboard.com/read.php?7,30070,30102#msg-30102 Not based on my experience when I changed the ones in my 02 Boxster 2.7l car...https://pedrosboard.com/read.php?7,30070,30102#msg-30102 MarcW Main ForumSun, 22 Sep 2013 16:44:02 -0400 https://pedrosboard.com/read.php?7,30070,30100#msg-30100 The 4 are identical in 986, different front vs. back in 987 *NM*https://pedrosboard.com/read.php?7,30070,30100#msg-30100 Boxsterra Main ForumSun, 22 Sep 2013 15:33:11 -0400 https://pedrosboard.com/read.php?7,30070,30090#msg-30090 The sensors consist of two electrical circuits: The actual sensor and the heating element....https://pedrosboard.com/read.php?7,30070,30090#msg-30090
While above in an earlier post I did say swapping sensors side to side is ok, what I meant is it is ok in the sense it is better than swapping them front to back and vice versa, but I really do not like messing with the sensors much and the electrical connector which is part of the harness even less.

My recommendation would be to replace both sensors with new sensors but very carefully and worry about further diagnostics if the new sensors fail to quell the error codes.]]> MarcW Main ForumSat, 21 Sep 2013 17:45:32 -0400 https://pedrosboard.com/read.php?7,30070,30089#msg-30089 Here is a link to our write-up on replacing the O2 sensor...https://pedrosboard.com/read.php?7,30070,30089#msg-30089Boxster O2 sensor replacement

Click on any of the images for a larger version.]]> RainyDayGarage Main ForumSat, 21 Sep 2013 16:00:51 -0400 https://pedrosboard.com/read.php?7,30070,30088#msg-30088 CEL'shttps://pedrosboard.com/read.php?7,30070,30088#msg-30088
If the code comes back, I will swap the sensors. that seems to make good sense.

If I am going to replace either of them, it makes sense to change them both at the same time.

That said, 60k seems a little early to start having problems. As a result, I am a little concerned that it might be something other than the O2 sensor]]> JM-Stamford,CT Main ForumSat, 21 Sep 2013 11:54:53 -0400 https://pedrosboard.com/read.php?7,30070,30087#msg-30087 I do not know about the OP's car but in my car the sensors are not exactly...https://pedrosboard.com/read.php?7,30070,30087#msg-30087
Swapping from side to side is ok. The other sensor while it is of the same age and so on is not manifesting any error and it is a shade tree test to "confirm" the suspected sensor is bad and the error is not due to something else.

There's always the risk of damaging the "good" sensor though. And with older cars the less use the connectors get subjected to the better I like it.]]> MarcW Main ForumSat, 21 Sep 2013 11:48:55 -0400 https://pedrosboard.com/read.php?7,30070,30080#msg-30080 Agreehttps://pedrosboard.com/read.php?7,30070,30080#msg-30080
If not then you swap the one with the error with one without the error and see if the error moves with the sensor. When doing that test it's better two swap the front with the back (as opposed to side-to-side) since -- as Marc suggests -- the one on the opposite side is likely also on its last legs.]]> Boxsterra Main ForumSat, 21 Sep 2013 09:20:54 -0400