P0446, P1124, P1126 CEL

[rick3000]

After six years of near flawless service my Boxster is having some trouble. Two weeks ago I noticed the car was occasionally idling a little rough when stopped. Mechanic said it was the MAF, replaced it. Got the car back and noticed it had trouble turning over every 5-6th time, mechanic said it could be the starter, maybe AOS related.

I then got a CEL P0446 (EVAP Canister Shutoff Valve (Function) - Below Lower Limit). This evening the car did not start the first try. It turned over the second time but it stalled after idling for 30 seconds. I finally got home and have two new codes P1124 (Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold) and P1126 (Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Rich Threshold). I just had the MAF replaced.

I am thinking it could be dirty fuel injectors. Any thoughts on this? My mechanic is only two miles from my house, is it safe to drive the car to him, or should I have it towed.

Thanks!

-Rick

[bar10dah]

Far be it for me to ever suggest to anyone to do a search for the information they're looking for. But, when the thread you start is nearly the exact same title as a thread only a few threads down the list on the main page... I just gotta laugh. And, I guess I'm beginning to understand all the old timers' frustrations. :)

http://www.renntech.org/forums/topic/32106-code-p1124-p1126-p0446/

[rick3000]

I did search and read through that thread, however the symptoms my car has are slightly different which could affect what the actual cause of the problem is.

[Loren]

Fault codes tell the story - your DME thinks the mixture is too lean so it tries to make it richer. It reaches it's max threshold because you have an air leak.

[rick3000]

Thanks Loren, do you think it's safe to drive until I can take it to the mechanic Monday?

[logray]

Yes, but I wouldn't go on a long road trip.

[bar10dah]

I did search and read through that thread, however the symptoms my car has are slightly different which could affect what the actual cause of the problem is.

I have nearly the exact same symptoms as you. But that's okay, as these symptoms point to a laundry list of root causes. So, your situation may not be exactly like mine. And that's even more evident as you read through all the previous threads about this issue. Persons A, B, and C solved their problems with these P-codes with solutions X, Y, and Z... The most common solution has always been some sort of vacuum leak, such as an AOS bellows tube or oil filler tube. However, others have solved their problems with MAFs or O2 sensors.

Still, a lot of good information from that thread I posted and the links within it. Such as, from one of the links, you'll notice that this code is a result of reaching maximum enrichment at or near an idle state. So, if the car doesn't spend much time at idle, it won't set a CEL. Case in point, I just drove nearly 1,700 miles last week, and the only time I got a CEL was when I was in stop and go traffic with extended idling. Hundreds and hundreds of miles of straight interstate driving and no CEL. Of course, this was with my particular problem. May not be the same for your car. As they say, "your mileage may vary."

Good luck with your troubleshooting and let us know how you do. If the mechanic tells you of a specific part to replace, come back here and one of us can help provide a DIY if you want to save some money on labor and parts costs.

Edited February 26, 2012 by bar10dah

[bar10dah]

Rick3000, whatever came of your problem?

[HELLAS59]

Hello Everyone.

I have a 1999 Boxster Tiptronic Base Model with the EXACT same codes. I am not very Mech Savvy which is why I am asking for you good folks to give me some guidance on these problems. I recently took the car to a nearby mechanic and he told me that I need to replace the Catalytic Converter (I ve had a really loud rattle for some time now) as well as a crank sensor that I am not familiar with. I guess my question is: can these codes P0446 P1124 P1126 be caused by the problems mentioned by my mechanic? Ive read that those codes most likely indicate an Air Leak, a bad AOS, dirty fuel injectors, and a few other reasons. I was quoted a bill of over $1700 to fix both problems. And if my Cat is rattling, does it necessarily mean that I need to replace the whole thing? If so, I have read online that the best route would be to buy used OEM. Any feedback/help would be greatly appreciated my brothers.

[JFP in PA]

Hello Everyone.

I have a 1999 Boxster Tiptronic Base Model with the EXACT same codes. I am not very Mech Savvy which is why I am asking for you good folks to give me some guidance on these problems. I recently took the car to a nearby mechanic and he told me that I need to replace the Catalytic Converter (I ve had a really loud rattle for some time now) as well as a crank sensor that I am not familiar with. I guess my question is: can these codes P0446 P1124 P1126 be caused by the problems mentioned by my mechanic? Ive read that those codes most likely indicate an Air Leak, a bad AOS, dirty fuel injectors, and a few other reasons. I was quoted a bill of over $1700 to fix both problems. And if my Cat is rattling, does it necessarily mean that I need to replace the whole thing? If so, I have read online that the best route would be to buy used OEM. Any feedback/help would be greatly appreciated my brothers.

 

More to the point, it looks more like you may need to replace your mechanic,

First of all, there are a lot of thing on the exhaust, like multiple heat shields that are famous for coming loose and rattling, so I would not immediately start thinking about replacing the expensive cat until appropriate diagnostics say you actually need one.

As for the codes, P0446 points to a problem with the EVAP canister shut off valve on the intake purge line, which could also cause a vacuum leak. P1124 and 1126 are both O2 sensor codes that indicate that your intake system (which is attached to the EVAP purge line) has a vacuum leak because the DME cannot enrich the mixture enough to get the fuel air ratio back in spec. None of this points to bad cats, just a problem valve and possible resulting air leak, and some otherwise poorly executed diagnostics.

 

[HELLAS59]

Thank you so much JFP for the quick reply. I may need to complain to him about the route he chose on diagnosing these problems. He seems to be a very reputable mechanic that works on a lot of Germanics as well. Nevertheless, I received the complete writeup from my mechanic and a Diagnosis Bill of $150 so that he could tell me about my P0446 P1124 P1126 CEL codes with written descriptions of each code. (Things I had already looked up online).

He listed the parts that need to be replaced which were:

*Converter, Exhaust Catalytic (Drivers Side).

*Sensor, Crankshaft Position

NOTE: No smoke tests were performed for Vacuum leaks. The Evap Canister was only mentioned in the writeup as one of the codes (P0446) that showed up and was listed as being: "Below Limit".

He also mentioned that the Drivers Side Cat seems to have been welded around the area that it has currently broken from, something that the previous owner must have done. (It lasted 7 years whatever he did).

A total of $1700 for the Bill...way too much I believe, especially for things that may not actually fix the root of the CEL codes problems.

Did I just get ripped off? What should my course of action be? Please my friends...any advice would be greatly appreciated !!

God Bless you all.

[JFP in PA]

Thank you so much JFP for the quick reply. I may need to complain to him about the route he chose on diagnosing these problems. He seems to be a very reputable mechanic that works on a lot of Germanics as well. Nevertheless, I received the complete writeup from my mechanic and a Diagnosis Bill of $150 so that he could tell me about my P0446 P1124 P1126 CEL codes with written descriptions of each code. (Things I had already looked up online).

He listed the parts that need to be replaced which were:

*Converter, Exhaust Catalytic (Drivers Side).

*Sensor, Crankshaft Position

NOTE: No smoke tests were performed for Vacuum leaks. The Evap Canister was only mentioned in the writeup as one of the codes (P0446) that showed up and was listed as being: "Below Limit".

He also mentioned that the Drivers Side Cat seems to have been welded around the area that it has currently broken from, something that the previous owner must have done. (It lasted 7 years whatever he did).

A total of $1700 for the Bill...way too much I believe, especially for things that may not actually fix the root of the CEL codes problems.

Did I just get ripped off? What should my course of action be? Please my friends...any advice would be greatly appreciated !!

God Bless you all.

 

Setting the exhaust system noise problem aside for a moment, long before I would tell a customer that he (or she) needs a very expensive  cat replacement, I would have done a cat efficiency test on the side with the noise.  This is a very simple and quick diagnostic that can be run with most (if not all) Porsche specific diagnostic systems that would provide a clear picture of how the unit is working.  As for the welding he has observed, I would need to see the cat to be able to say if that is OEM of something done at a later time.  But would also note that all of the factory cats have obvious and often crude looking welds on them from the factory:

 

 

 

Moving back to the codes themselves, P0446 indicates a problem with the valve that is supposed to seal off the air purge line running from the EVAP canister to the intake system.  These valves are known to become problematic, often because of build up in the purge lines that eventually breaks loose and jams the valve itself.  While they often can be cleaned out, it is usually best to simply replace them while also blowing out the purge line itself, as they have to be removed to clean them and they are not that expensive.  The P1124 and 1126 codes indicate an overly lean condition on both cylinder banks.  Overly lean conditions are not a catalytic converter related fault, and as they exist on both banks, it cannot be caused by a bad cat on only one bank.  They are typically the result of an air leak in the intake system, which would lead you back to the failed airline purge valve.  And as I mentioned previously, many times exhaust rattling complaints on Boxster are the result of the multiple heat shields coming loose, which simply need to be reattached.

 

While it is not my place to question the amount of the repair bill as I have no reference to the shop's hourly rate or replacement parts pricing, my larger concern would be that the correct parts were replaced and that the problems did not return, as I am having difficulty tying what the codes say to your mechanics repair track.

[HELLAS59]

Thank you so much JFP !! I really appreciate all your help. What is your opinion on the crankshaft position sensor that he said needs to be replaced?

[HELLAS59]

Also JFP...if possible....do you think you can point me towards which "valves" I should purchase so that I can replace or maybe give me a part number. Again, I have '99 Base model auto. Do you think I would need to buy the entire Evap Cannister itself? Ive read that its located in the front passengers side wheel well, is that where the valves in question are located as well? Also, is the purge line in question connected to the actual Evap cannister? And would blowing air from an air compressor be a sufficient way to clear the line in question. Any detailed information would be greatly appreciated as I will try to do this sometime soon. I have changed my Air filter and am thinking of cleaning my Maf as well, but it looks very clean, even though my Air filter was filthy, do you think it would be a good idea to go ahead and spray it with Maf Cleaner either way and let it dry...heard u have to be exteemely careful with those things as they are very sensitive. And while Im gonna have the engine engine panel removed, is there any advice on what I should look out for as far as any vacuum leaks may be concerned etc...or any method to diagnose the hoses there? Im basically trying to do some basic troubleshooting before I get to the Evap issue. Again, thank you so much for all your help !!

[JFP in PA]

The CPS may or may not have needed changing, as it is difficult to tell without actually seeing the car.  But in any case, the CPS is unrelated to the codes you are seeing.

 

This is a diagram of the entire EVAP system on your car, which shows all of the components and where they are located.  The purge line can be cleared with compressed air:

 

 

As for the current part numbers, I would suggest checking with your local dealer as they may have updated with superseded numbers.

[HELLAS59]

*Boxster CEL Light Info*

Purge valve rear in engine

Hello JFP in PA and to everyone else. I was gone for a little while and wasnt driving my boxster. Ive been back for a month now and had some work done on the car. Replaced coolant expansion tank with oem part, hasnt solved my cooling problem fully...never the less this thread is about the evap cannister and lean condition codes so ill keep to that and greatly appreciate your guys' input because this problem is driving me crazy. So my mechanic recently changed my Aos, said it was completely gone and saw it smoking a lot during the smoke test. So obviously thats the major leak area that needs to be fixed. He installs a new oem part and the car is running better, no hard starts, idle has become more normal, and generally the car runs better...great. So on the drive back home (30 mins away) my CEL light comes back on (I stopped for gas btw on the way home) and when I get to the house I read the codes and sure enough they are p0446 p1124 & p1126. Evap code & Lean condition on both banks (Im sick of these codes). I go the next day and was a little late so we didnt have time to diagnose the car and the problem so we remove MAF so that I may drive the car around for two days to see if maybe it will help the car reset. Meanwhile the car is developing a few hard starts and turns off every so often when running, idle is becoming a little more shaky, and my nerves are outta control while watching all these things occur. I reinstall MAF two days later, reset codes and take the car back and my mechanic does a 3 hour diagnostic with me by his side. CEL has not come back on yet. My mechanic uses his diagnostic tool and noticed a two codes through his machine that read:

96) Shutoff Valve, Activated Charcoal Filter (Final Stage) No Signal

98) Tank Vent Valve No Signal

He is a really good mechanic with experience on Porsches Bmws Audis and German cars in general. I asked him about pushing compressed air through one of the evap lines and he has never heard about that being done and doesnt know how good it could be for the car. Can someone put an arrow on the diagram to show me exactly which line needs compressed air to be run through so that it could clear any possible blockages? I would like to know exactly so I can show it to my mechanic. Isn't compressed air through that line part of the porsche diagnostic protocol when dealing with an evap system problem with a p0446 code? Next time I go I would like to show him exactly. Anyways, he spent 3 hours doing diagnostic work. Took out front right wheel and liner and exposed evap system. Took out the valve and tested it, and said it was fine, then he tested the valve in the rear compartment, which apparently stays closed except when it does a test with every ignition start, it starts clicking open and closed he told me..is this correct guys? While doing these diagnostics the car shut off, we had it running on the lift, we restarted the car and my mechanic quickly went over to the gas cap (which is also oem new) opened it, and listened for suction, sure enough there was a loud sucking noise in the gas filler area. So he told me the problem is intermittent, its hard to detect because it is intermittent. He really believes that changing both Valves would be a great idea as they may be getting stuck every so often and causing this problem, but he told me that he really has a hunch that it is the one in the rear engine bay area. Should I shotgun replace the valve in the back and see if that will solve the problem? Ive spent so much money on the car and would just like this problem to go away once and for all. During the smoke test, there were really small leaks of smoke coming out, one on the J hook style line that connects from the Aos to the engine, and another small amount of smoke from the actual end of the line/hose that runs from the engine all the way to the front of the evap cannister. He told me those two small leaks are not significant enough to be causing the current problems. So let me know guys. If you need pictures or have more questions/clarification feel free to ask me...I really need all the help I can get. Thanks in advance to all of you and God Bless you!!

Edited February 6, 2016 by HELLAS59

[JFP in PA]

Hello JFP in PA and to everyone else. I was gone for a little while and wasnt driving my boxster. Ive been back for a month now and had some work done on the car. Replaced coolant expansion tank with oem part, hasnt solved my cooling problem fully...never the less this thread is about the evap cannister and lean condition codes so ill keep to that and greatly appreciate yalls input because this problem is driving me crazy. So my mechanic recently changed my Aos, said it was completely gone and saw it smoking a lot during the smoke test. So obviously thats the major leak area that needs to be fixed. He installs a new oem part and the car is running better, no hard starts, idle has become more normal, and generally the car runs better...great. So on the drive back home (30 mins away) my CEL light comes back on (I stopped for gas btw on the way home) and when I get to the house I read the codes and sure enough they are p0446 p1124 & p1126. Evap code & Lean condition on both banks (Im sick of these codes). I go the next day and was a little late so we didnt have time yo diagnose the car and the problem so we remove maf, and I drive the car around for two days to see if maybe it will help the car reset. Meanwhile the car is developing a few hard starts and turns off every so often when running, idle is becoming a little more shaky, and my nerves are outta control while watching all these things occur. I take the car back and my mechanic does a 3 hour diagnostic with me by his side. He is a really good mechanic with experience on Porsches Bmws Audis and German cars in general. I asked him about pushing compressed air through one of the evap lines and hes never heard about that being done and doesnt know how good it could be for the car. Can someone put an arrow on the diagram to show me exactly which line needs compressed air to be run through so that it could clear all blockages? I would like to know exactly so I can show it to my mechanic...and isnt that part of the porsche diagnostic protocol when dealing with an evap system problem with a p0446 code? Next time I go I can show him exactly. Anyways, he spent 3 hours doing diagnostic work. Took out front right wheel and liner and exposed evap system. Took out the valve and tested it, and said it was fine, then he tested the valve in the rear compartment, which apparently stays closed except when it does a test with every ignition start, it starts clicking open and closed..is this correct guys? While doing these diagnostics the car shut off as we had it running and when we started it back up while on the lift, my mechanic quicjly went over to the gas cap (which is also oem new) opened it and listened for suction, sure enough the there was a loud sucking noise in the gas filler area. So he told me the problem is intermittent, its hard to detect because it us intermittent. He really believes that changing both Valves would be a great idea as they may be getting stuck intermitently and causing this problem, but he told me that he really has a hunch that its the one in the rear engine bay area. Should I shorgun order and have him replace the valve in the back? During the smoke test, there were really small leaks of smoke coming out, one on the J hook style line that connects from the Aos to the engine, and another small amount of smoke from the actual end of the line/hose that runs from the engine all the way to the front of the evap cannister. He told me those two small leaks are not significant enough to be causing the current problems. So let me know guys. If you need pictures or have more questions/clarification feel free to ask me...I really need all the help I can get. Thanks in advance to all of you. God Bless you!

 

OK, as for the lines to blow out, refer to my system diagram above, you want to blow out lines 1 & 3 after disconnecting both ends of the lines.

 

As for your mechanic's comment that "those two small leaks are not significant enough", I'm sorry but that is nonsense.  Any vacuum leak is significant, this system has to be tight.  You could easily have a few "small" leaks that are in fact equivalent to one massive leak.  And by your comment about the AOS J line, are you referring to the one that runs from the top of the AOS to behind the throttle body, or the long one that runs from the other side of the AOS and under the intake manifold?

[HELLAS59]

Thanks for the quick reply JFP in PA! A video tells a thousand words...glad I took these while my mechanic was smoke testing yesterday. Let me know what you think. Thanks in advance, appreciate it!

https://sendvid.com/upe1f6ey

https://sendvid.com/i1e020wf

[JFP in PA]

I think you have leak that needs to be fixed.

[HELLAS59]

Are those two leaks significant enough to cause my problem?

[JFP in PA]

Without knowing the volume of air they are passing, and answer is not possible.  But they are leaks that should not be there, and leakage effect is cumulative across all leaks, and in the second video you had considerable smoke billowing up at the beginning of the video, which is not a small leak.

[HELLAS59]

JFP...in the second video that area where the smoke is coming out a lot is the air filter area...is that not normal? My mechanic said it was for that area. Please let me know if its not suppose to be coming out from there! Thanks. Sorry for the late reply btw, didnt notice that you had replied on the next page. Again, thank you for all your feedback, I really appreciate it! Im going nuts with the car. My mechanic has changed my resovoir tank twice already with an oem part and I STILL have a leak, tried to take it out today and the red light for low coolant came up...seems like every two weeks or every couple hundred miles it just loses coolant. Im really stressed out from that and of course these CEL lights. I got the Aos changed for a second time in 3 years as well. I just want it to run kinda normal again

[JFP in PA]

JFP...in the second video that area where the smoke is coming out a lot is the air filter area...is that not normal? My mechanic said it was for that area. Please let me know if its not suppose to be coming out from there! Thanks. Sorry for the late reply btw, didnt notice that you had replied on the next page. Again, thank you for all your feedback, I really appreciate it! Im going nuts with the car. My mechanic has changed my resovoir tank twice already with an oem part and I STILL have a leak, tried to take it out today and the red light for low coolant came up...seems like every two weeks or every couple hundred miles it just loses coolant. Im really stressed out from that and of course these CEL lights. I got the Aos changed for a second time in 3 years as well. I just want it to run kinda normal again

 

If that smoke is coming from the air filter box, which is not evident in the video, it is normal.

 

As I mentioned, the problem of small vacuum leaks is that their cumulative impact can be large; you need to track them down one at a time and eliminate them.  These cars are rife with plastic vacuum lines that chafe or crack with age and drive shops nuts trying to track down the leaks.  When we get a bad case in the shop, we often resort to pulling off the intake and running all new plastic and rubber lines, just to eliminate all possibilities.  Not a cheap remedy, but one that works.

 

You need to also be careful about where replacement parts come from, particularly the vacuum reservoir tank and the AOS.  We have had so many issues with aftermarket units that we no longer will use them.  The AOS is particularly bad in this respect.  Even with factory units, we still vacuum test every AOS we install, just to be sure, as we have also had some problem OEM units as well.  A fresh, correctly functioning AOS should pull between 4-7 inches of water on a cold start, then settle down to around 5 inches as the car warms up.  If we put one in and it does not meet those criteria, it comes back out again and another new one goes in, otherwise you can get problems ranging from vacuum leaks to high oil consumption.  We have also seen vacuum reservoirs that seemed good in the car, but completely fail a bench vacuum test as well. 

 

You also need to be aware that there are systems that are not in their normal operational modes unless the car is running, the EVAP control system is a perfect example.  With the car shut off during a smoked test, the control valves are not in the same position as they are when it is running, which can lead to erroneous conclusions.  There is also a EVAP check valve under the intake that is notorious for causing problems which can only be tested on the bench.  So a static smoke test cannot be the sole determinant of what is wrong, you need to dig further.

 

Your comment about the coolant system concerns me.  Early Boxsters with the 2.5L engine had cylinder liner issues that ranged from liner slippage to complete liner failure (commonly referred to as "D-chunking").  A completely tight cooling system can go literally years with no additional coolant required.  Something is not right; youe cooling system needs to be pressure tested, and you need to find out where the coolant is going.

[HELLAS59]

Thanks for the info JFP. The reservoir tank & AOS are all OEM parts, my mechanic wont allow anything else to be installed. The second reservoir tank has been pressure tested and inspected multiple times and there is still no sign whatsoever of any leaks. In saying that, once I drive the car for over 15 minutes and get on the highway for instance, if I put my windows down I swear I can smell a sweet coolant smell coming in, and its not just a little bit, at times its overwhelming. Could it be that whatever leak is occuring is happening when the car reaches a certain temperature or level of performance, and if it was a problem in the rear, why would I be smelling it coming from the front (When I open the windows going 70mph for instance, Im assuming that something from the front has begun to leak due to the way air is pushing the smell into the car from my windows, I may be wrong about this, but logically thats what one would think). This coolant problem is driving me crazy, every 100-200 miles I get the red light indicating low coolant, and when I look back at the tank once the car has cooled off it looks about 3-4 inches lower than where it should be. Ive removed the bumper before changing the reservoir tank the first time and cleaned up the radiators. Everything looked good to my untrained eye. Im using the latest cap that I bought brand new for the new tank as well. Could it be a hose that has a small tear that expands & drips coolant when the car is at a certain temperature? Once I slow down from a highway ride or come to a stop, I notice the coolant temp gauge creeping a considerable amount past the middle (my cars coolant temp was always dead center before this problem started occuring). I also had the thermostat changed with an OEM one as well as the water pump a year ago with an OEM part. Got those two things rechecked and everything looks and sounds fine.

Back to the vacuum leaks. When you say you cant see everything when the car isnt running, can you smoke test with the car running? No right...?? What other test can we do? I want this darn CEL light to finally go away and for the car to be running good again. Ive spent a couple thousand dollars the last few months just trying to accomplish this. The AOS was bad and was changed with an OEM one 3 years ago with a different mechanic. Recently had it changed AGAIN with my newer mechanic. Those two areas that you saw in the videos are the only two spots thag seem to have minor leaks. My mechanic swears he believes it to be the check valve that I think you are referring too as well that is faulty. Its under the intake like you said, I dont know what you mean by under the bench, but he put his electrical tool on it and at one point the readings came back messed up which made him believe that thats what is the main problem. I dont know what to do anymore. I want to fix everything so I can sell the car and maybe upgrade to a newer Boxster. Then again I have thrown and am throwing so much money into the car, not to mention that I love it so much (its my baby) that I may even keep her. I just want the car running well again. I never heard of this D-chunking before...sounds like a major problem. If coolant was mixing with oil, wouldnt I see that on the oil cap, at least thats what Ive read, and my mechanic hasnt seen any signs to suggest any engine flaws. How can we check for that? Also JFP, I wanted to ask you, where in PA are you? I would def drive up to you and have you look at the car for me, you seem to know more than anyone else. Of course I would pay you as well as buy you a couple of cold ones for your help! Im in Northern VA close to DC so if you are in southern PA I would love to come up to you to have a look, if I can make it there! Thanks for all your help and advice, I really appreciate every bit of it. I need all the help I can get at this point. Awaiting your reply to see if I could get anymore answers through the info I just provided you. Thanks!

[JFP in PA]

Yes, you can smoke test components on a running car, you need to do it with a small wand which you place near the suspected item and see if the smoke is drawn in.

 

The EVAP check valve is like a light bulb, it either works or it does not.  You pull it out and see if it closes when it should; if it does not, replace it.  Usually, they are stuck open by carbon build up, which cannot be cleaned out.

 

D Chunking is the failure of the cylinder liners near their ends.  This is an extreme example of what can happen:

 

 

In its early stages, the chunk is still there, but the liner is cracked and allows the engine to pull coolant into the cylinder.

 

I have addressed your other questions in a PM.