Hi folks - I have a 2000 Boxster w/ about 75k miles on it. Not much has been fixed/replaced in terms of the motor in all that time. The AOS was replaced about a 1.5 yrs back - that's it.

The CEL light came on and has stayed on. The car is running normally - no issues now.

I purchased an OBD2 code reader (Ancel AD310). The code it showed is"P1126" (might have read "P1126 $11" if that means anything - not sure the "$11" was smaller digits on the readout. It also said "Oxygen Sensing".

I don't have much confidence to work on the motor myself. But wanted to ask here:
1) is this code something to worry about? i.e. how serious to get fixed right away?
i realize it's emissions related, just not clear how likely it could be to end up causing a more serious issue (i.e. car stops running .....or at least starts running really badly....or causes more damage to the car, so much so that i should have fixed it right away)

2) if there are more diagnostics type info my particular code reader could pull, that are needed to answer the above question, let me know please, and i'll try to find that out (I think it may have that capability but wasn't sure how to pull it)

Thanks in advance

1) Air intake leak (has any work been done in this area?)
2) Fuel pressure
3) Fuel injectors contaminated

I would try:
- Check oil cap is on straight and on all the way
- Running a bottle of Techron Fuel System Cleaner (not "fuel injection cleaner") through and see if the code goes away.
- Check the intake for leaks

None of the causes is likely to cause any major issues unless you have a major intake leak, in which case you'll probably see drivability issues.

Thanks for the feedback Boxsterra.
(There's been no work of any kind on the air intake on this car, except maybe an air filter replacement once years back. The oil cap was/is on fine/secure.)

then hose connections are the suspect. Things age as well as wear. Especially plastic and rubber.

Now that you have the code understood, the code reader should be able to clear the code. If so, does it come back?

I had one of these, and we (or rather my mechanic) never did figure out what it was caused by but by wiggling things around looking, we must have re-snugged a connection that had worked loose. It was fine for the next 5 years.

Sometimes rodents like to chew wiring. Several people on this board have had that problem.

Thanks mikefocke
I haven't tried to "clear" the code as a total newbie to this. I take what you said as sound - checking things are snug, etc.

If anyone has a good video showing how to get to the engine compartment on the Boxster please share. I have experimented w/ that a few times but always got to a point where I couldn't "pry" some part of that cover/top away (fearing I would break something if i didn't watch out). Just getting the car to that point where you could stand a chance to see the things to check is a major bottleneck to me still.

There are several videos on Youtube.

Here's one.
[www.youtube.com]

... it offers a lot of detail and step-by-step:

[pedrosgarage.com]

Happy Boxstering
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

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bb1
Hi folks - I have a 2000 Boxster w/ about 75k miles on it. Not much has been fixed/replaced in terms of the motor in all that time. The AOS was replaced about a 1.5 yrs back - that's it.

The CEL light came on and has stayed on. The car is running normally - no issues now.

I purchased an OBD2 code reader (Ancel AD310). The code it showed is"P1126" (might have read "P1126 $11" if that means anything - not sure the "$11" was smaller digits on the readout. It also said "Oxygen Sensing".

I don't have much confidence to work on the motor myself. But wanted to ask here:
1) is this code something to worry about? i.e. how serious to get fixed right away?
i realize it's emissions related, just not clear how likely it could be to end up causing a more serious issue (i.e. car stops running .....or at least starts running really badly....or causes more damage to the car, so much so that i should have fixed it right away)

2) if there are more diagnostics type info my particular code reader could pull, that are needed to answer the above question, let me know please, and i'll try to find that out (I think it may have that capability but wasn't sure how to pull it)

Thanks in advance

Generally speaking the code is something that you should worry about. I say "worry" in the sense the engine controller has detected a problem something out of the norm. In this case the engine, at least one bank, is running too rich and the controller has reached its limit as to how lean it can go.

Through the wonders of technology the engine controller can relay this information to you via the CEL and the error code.

There is the risk that the condition deteriorates and the engine does run worse. Or the CEL flashes which is a more serious indicator of problems. The converters then could be at risk of damage.

For some reason the engine, well, one bank at least, is being fed too much fuel. This can be due to a fuel pressure problem but it can be also due to a mis-behaving MAF that is inaccurately measuring the amount of air being used by the engine.

(Why the error does not arise from the other bank is because often an engine's two banks have some variation and one is more sensitive to incorrect fueling than the other.)

Yet another possibility is an injector is not operating properly. Fuel system deposits can dislodge and possibly interfere with the injector's abiilty to close/seal the tip completely. This can be a transitory problem. As can be an injector that for some reason acts up in such a way to cause more fuel to be injected. (The injector "sticks".)

There is not much a layman can do in this case.

Without an OBD2 code reader and data viewer and some knowledge of how to work on engines about all I can do is echo the advice you have already received and recommend try a bottle of Techron. Use according to directions. That is the bottle I buy treats 20 gallons but I just dump the entire bottle into my car's fuel tank (approx. 16+ gallons) and then fill up the fuel tank. Drive the car normally.

The general rule is if the engine exhibits any improvement -- and my experience is it can -- use a 2nd bottle when the fuel tank level with the 1st bottle gets low enough you have to add gasoline.

After using Techron the advice I received and pass on is to change the oil/filter. Techron can result in more contamination of the engine's oil and the last thing these engines need is more contaminated oil.

Folks thanks for being so helpful here - it's really nice that this community exists. The video showing how to access the engine, I hadn't seen and looks helpful so I'll be checking this out soon.

Is it 100% safe to use that Techron Fuel System Cleaner? Common sense tells me it is. Just w/ this brand of car, I know it has to be cared for precisely or you end up in a world of hurt at the dealer hence I ask.
Thanks

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bb1
Folks thanks for being so helpful here - it's really nice that this community exists. The video showing how to access the engine, I hadn't seen and looks helpful so I'll be checking this out soon.

Is it 100% safe to use that Techron Fuel System Cleaner? Common sense tells me it is. Just w/ this brand of car, I know it has to be cared for precisely or you end up in a world of hurt at the dealer hence I ask.
Thanks

When used correctly Techron is as safe to use as anything you regularly put in the engine like fuel or oil. But unlike fuel or engine oil I wouldn't feed the engine a regular diet -- like every fuel tank -- of a bottle of this stuff.

I used to in a mild way argue against adding a fuel system cleaner except in rare cases preferring I thought to keep the engine clean "organically" by driving the car. As I have experienced upon taking one of my cars out on the start of a longish road trip after the 1st leg and having to fill up the fuel tank after possibly a few hundred miles of highway/freeway driving the engine would be running noticeably better. This highlighted to me that even though my regular usage consists of a 30 mile drive to then from work and mostly highway miles and often at highway speeds (at other times traffic can have my driving slower than the speed limit) this was not sufficient to keep the engine clean "organically".

More recently just how "inadequate" my usage is I switched from using Shell V-Power (premium) to Chevron premium gasoline. After just a few tanks of fuel I noticed the Boxster running markedly better. Low end was improved as was throttle response. My usage remained unchanged. The difference was the presence of Techron in the fuel.

As an aside, Porsche techs I spoke to about this said that was their experience too. While some didn't run Chevron gasoline on a regular basis one in particular preferring Shell because by his (butt) dyno the engine made more power running Shell gasoline he told me every once in a while he'd run a tank of Chevron gasoline for its detergent benefits. (I didn't really notice any HP increase/decrease between Shell and Chevron but my (butt) dyno many not be as sensitive as the tech's.)

In the case of your car and the engine a bottle of Techron is about as much as you can do without putting wrench to the car.

If you are in any way concerned though don't use the Techron. Or before using it at least consult with your trusted Porsche tech and get his advice.

Hey folks - someone here suggested using the Techron Fuel System cleaner and then seeing if the code goes away. So should I "clear" the code w/ my code reader (before putting in the fuel cleaner stuff and running thru a tank of it)? I saw that was an option available but wasn't 100% sure it's advisable to do that, though it seems like it is a pretty benign thing to do.
Thanks

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bb1
Hey folks - someone here suggested using the Techron Fuel System cleaner and then seeing if the code goes away. So should I "clear" the code w/ my code reader (before putting in the fuel cleaner stuff and running thru a tank of it)? I saw that was an option available but wasn't 100% sure it's advisable to do that, though it seems like it is a pretty benign thing to do.
Thanks

My comments about Techron were in no way suggesting you use Techron in lieu of properly tracking down the cause of the P1126.

The error code arises because the DME is at its enrichment limit. IOWs, the engine (bank) was found to be running lean, too lean, and the DME had to add fuel and it reached the limit of how much it could add before the leaness condition went away.

It is a low RPM lean condition. (Engine RPMs are below 880 RPMs.)

The possible causes are Intake system leaking. Fuel pressure too low. Fuel injectors contaminated. Volume supply of fuel pump too low.

Unless you are a rather experienced/skilled DIY'er properly diagnosing the above possible causes is something you should let a professional tech do.

My experience with lean conditions at idle has been the cause was due to a failing AOS (however, only one of the 3 that have failed caused any CEL to come on), and a leaking oil filler tube cap.

In the case of the AOS the CEL would come on at the end of the day while I was just leaving the freeway after driving the car all day on teh freeway just dashing off and back on again for fuel. The engine would produce just the hint of a stumble concurrent with the light coming on. This behavior continued a couple of days as I covered 2K miles. After I reached my destination the next day at the hotel when I cold started the engine the exhaust just billowed oil smoke. I knew then my diagnosis of "MAF" was woefully wrong and it was instead the AOS.

The leaking oil filler tube cap was a bit of trouble. The CEL would come on usually after I had driven 30 miles from home to the office or more often from the office to home. And it would come on very close to home. MAF was my preliminary diagnosis (guess) and this was re-inforced when once or twice the error codes were for a too rich condition.

Convinced it was the MAF I replaced this, but the error came back. Proved to be the oil filler tube cap leaking and it only leaked enough at low engine speed to be a factor. What fooled me into thinking it was the MAF was what would happen is the DME would go almost to the limit adding fuel maybe even over the limit but before it could decide to set an error code the cap would stop leaking. Then the DME would have to remove fuel. It would do so and reach its limit on removing fuel and set a too rich error code.

My Boxster has never manifested an intake proper leak. And while the fuel pump quit it did so with no drama no lingering. The car has never had any fuel delivery or fuel pressure problems and even with a low fuel tank -- while I don't make a habit of driving the car with too low a fuel level in the tank once in a great while the level does get pretty low -- had never manifested any CEL or even any engine symptoms.

Now because one of the possible caues is contaminated fuel injectors Techron could possibly make sense. But Techron takes time to clean the injectors. Pretty much you would have to run quite a bit of the fuel treated with Techron through the engine.

Frankly while contaminated injectors is listed as a possible cause I put contaminated injectors pretty far down the list. My money would be on an AOS (even though it is just 1.5 years old; I'm thinking premature failure or possibly an installation problem); a leaking oil tube filler cap; a leaking oil filler tube. Less likely an intake leak but if this was touched.... At the bottom would be fuel pressure/supply. A trained tech could check for these conditions easy (relatively speaking) enough and at least one would know. A failing AOS is hard to "spot".

Techron will take a while (likely hundreds of miles of varied driving) to resolve the problem. Until that time the CEL will recur. Once the car has gone through a couple of drive cycles with no error, the CEL will go away. That is the moment when you throw a party.

thanks Boxsterra