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Here's my take. All your O2 sensors are fine because you saw them operating correctly most of the time. If one of them is bad in Bank 1, they should not flat line at the exact same time. So I tend to agree with you that the flat line truly means air leak in Bank 1. Also, the DME never flagged any persistent O2 sensor codes so far. The code P1126 was persistent (btw, P1146 was a typo?) You could swap the precat sensors between the banks to verify the above easily.

 

The air intake manifold clamps in bank 1 are strong suspects. Maybe reinstall the plenums and the clamps?

 

Other sources of air leak include AOS and evap purge valve but I would think those should affect both banks. It won't hurt to cover them as well. You will need a manometer to verify proper engine crankcase vacuum (5" water). You can remove the evp purge valve and use a 9v battery to operate it and see if it's sticky and/or leaking.

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Latest strange events (and yes, P1146 was a typo, 1126 is correct):

This morning I again swapped the upstream O2 sensors to try to determine if I had right bank lean issue or O2 sensor problem. I then went for a drive to the local Porsche dealer, about 20 minutes, while monitoring the sensor voltages . Both sensors seemed to working, similar outputs, no flatlining. When I got to the dealer I checked for codes and lo and behold, the pending P1126 was gone, but there was a pending P0139, bank 1 sensor slow response.

Late this evening, I went out to drive around. After ten miles, the P0139 pending code persisted, so I cleared it. I then drove almost 50 more miles, and the pending code did not reappear. My readiness monitors are all set except evap and that pesky SAI. Now that the other problems are in abeyance, I'll try the SAI diagnoses suggested earlier in this discussion using the BlueDriver.

I think I may have an intermittent vacuum leak problem on bank 1, so no more jerky driving for now!

Thanks once more to everyone for taking the time to make suggestions, and I'll keep you posted.

Edited by mesutter

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That's interesting. P0139 is bank 1 postcat sensor. Lets see how the SAI diagnosis go.

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Yes, and it's the most difficult one to change due to the proximity of the Tiptronic plumbing on that side.

I'm going out now to start driving around. I'll capture the start-up O2 voltage data (air pump on and about 30 seconds beyond). My BlueDriver can capture the data and save it as a spreadsheet, but I don't believe it can directly output a graph. It does show it graphically on the screen, so I'll also grab a screenshot. I don't currently have a spreadsheet program on my computer to graph the data.

Edited by mesutter

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Sounds good. Just make sure you log at least until the SAI pump stops.

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Just drove an additional 50 miles, no codes nor pending codes. EVAP and SAI still not ready.  I clicked on the wrong button and lost the cold start voltage data logs, but I did get screenshots of the approx 2 1/2 minutes after cold start. The air pump shut off at about 1:48 into the log.  The first two graphs (image 2 and image 3A) are of the cold start in portrait and Landscape mode. The blue line is the Bank 1 downstream O2 sensor (B1S1), and the red line is the Bank 2 downstream sensor (B2S2).  The third graph (image 4) is shows output from about 1 1/2 minutes steady running at approx. 40 mph and 30 seconds or so at idle in drive.

 

There is an obvious difference between the reaction of the Bank 1 downstream O2 sensor and that of Bank 2 upon Air Pump shutoff.  The Bank 1 sensor is, of course, the one that threw the pending P0139 code which has not reappeared after being cleared.  Is it likely that the reaction of the problematic sensor is preventing SAI readiness?

 

 

image2.pdfimage3A.pdfimage4.pdf

Edited by mesutter

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Excellent! I agree with your diagnosis that the current bank 1 postcat sensor is bad (aged) because at cold start, there is no reason why it reacts much slower than the bank 2 postcat. It didn't detect O2 until the pump is off. By the time it's too late so the DME thought bank 1 didn't receive the O2 injection. If the bank 1 SAI ports are blocked, the postcat should read rich a/f (high voltage) instead at cold start but it didn't. You can again switch the postcat sensors and see if the slowness follow the sensor.

I think it's worthwhile to get a new bank 1 postcat sensor to further diagnose the issue. Use the bosh online part catalog to find the part # then check Amazon, which has great price for Bosch O2 sensors.

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The right rear is a ***** to change because of the Tiptronic plumbing proximity, so no more swapping. I'm off to O'reilly because they can get me a Bosch 15183 (Porsche OEM # 986 606 128 01) for $121 and I'll have it tomorrow. That's $30 more than Amazon, but worth it to get it done sooner.

Thanks for all your help and amazingly fast responses, Ahsai!

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Judging by the censoring on my last post, one is not allowed to refer to female dogs on this forum!

There goes my reputation even before it was established!

Part ordered, will have it by noon tomorrow!

Edited by mesutter

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Thanks to you and Loren. The terms "for a certain time and under certain driving conditions" are a bit vague. Any definitive drive cycle that is as specific as that for the 993?

Loren says "all 5 criteria must be met to have system readiness for smog tests". In my case, my reader showed a ready condition on all monitors EXCEPT secondary air. California will allow a year 2000 and up car to be tested with the evap monitor pending, but no others.

As mentioned previously, the car has to go through a number of cold starts, full warm up, drive at highway speeds, shut off, and full cool down cycles before it resets. People have promoted specific regimens like the one you mentioned for the 993 from time to time, but I am unaware of a specific one that works consistently on the later cars.

My experience belies this. I had all readiness monitors reset except EVAP and SAI. With the help of Ahsai and the O2 voltage readings at cold start-up, it was judged that the slow response of one of the post-cat sensors was the likely culprit. So today, I put in a new Bosch sensor, started the car and ran it through a cold start cycle for 2 and 1/2 minutes sitting in my driveway. I then scanned the DME for smog readiness, and lo and behold, the SAI readiness check was complete and reset! So at least for my 2001 Boxster with a 7.2 DME, running a full drive cycle is NOT necessary to complete the SAI test and remove the flag. BTW, EVAP is still not reset, but that is not necessary to pass smog in California.

I immediately drove to my long time smog tester who tested it and it passed- hooray!

Thanks so much Ahsai and all the rest of you who have so generously taken the time to read my lengthy posts and offered their expertise, suggestions and insight. This forum is so much better in that regard the some of the others that I also posted on.

Edited by mesutter

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Well done, and you passed !

So to fix an SAI system rediness-fault , the fix was a post-cat O2 sensor?

Just wanted to close the story because in the beginning this seemed like a very obscure and difficult case.

Edited by Schnell Gelb

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Thanks to you and Loren. The terms "for a certain time and under certain driving conditions" are a bit vague. Any definitive drive cycle that is as specific as that for the 993?

Loren says "all 5 criteria must be met to have system readiness for smog tests". In my case, my reader showed a ready condition on all monitors EXCEPT secondary air. California will allow a year 2000 and up car to be tested with the evap monitor pending, but no others.

As mentioned previously, the car has to go through a number of cold starts, full warm up, drive at highway speeds, shut off, and full cool down cycles before it resets. People have promoted specific regimens like the one you mentioned for the 993 from time to time, but I am unaware of a specific one that works consistently on the later cars.

My experience belies this. I had all readiness monitors reset except EVAP and SAI. With the help of Ahsai and the O2 voltage readings at cold start-up, it was judged that the slow response of one of the post-cat sensors was the likely culprit. So today, I put in a new Bosch sensor, started the car and ran it through a cold start cycle for 2 and 1/2 minutes sitting in my driveway. I then scanned the DME for smog readiness, and lo and behold, the SAI readiness check was complete and reset! So at least for my 2001 Boxster with a 7.2 DME, running a full drive cycle is NOT necessary to complete the SAI test and remove the flag. BTW, EVAP is still not reset, but that is not necessary to pass smog in California.

I immediately drove to my long time smog tester who tested it and it passed- hooray!

Thanks so much Ahsai and all the rest of you who have so generously taken the time to read my lengthy posts and offered their expertise, suggestions and insight. This forum is so much better in that regard the some of the others that I also posted on.

 

 

Last week, we had a 2001 base car in the shop for emissions inspection that finally reset the SAI flag after 87 miles of driving over multiple days.  And I've seen cars longer that that as well.  It doesn't always work itself out with one run cycle.

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Yes, that change led to the SAI readiness monitor showing completed.

The other pending and full problem codes popping up during the arduous process indicate there may be other latent troubles, in particular there may be an intermittent vacuum leak (reference the pending P1126 code that popped up after a abrupt stop) or a CAT on the way out (reference the P0420 code). But if so, at least they were in abeyance long enough for me to pass smog.

I'll clicked the problem solved button.

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To JFP in response to: "Last week, we had a 2001 base car in the shop for emissions inspection that finally reset the SAI flag after 87 miles of driving over multiple days. And I've seen cars longer that that as well. It doesn't always work itself out with one run cycle."

Perhaps it has to do with how responsive the post-cat sensors are. If they are old and slower, it may be that the DME just misses getting the info it needs to set the SAI as "ready". After all, they only have about a minute and a half to detect and signal the air pump's oxygen arriving in the manifolds. Did you do a scan on the O2 voltages during cold start on the vehicle that took 87 miles? After changing my right rear, the scan was dramatically different. All of a sudden, the left rear was (noticibly) the laggard, whereas the right had been before.

When the SAI flag is slow, it may not be the miles driven, but the additional cold starts, the final one conveying the DME required info, that leads to the reset. Continous test readiness monitoring while driving, or at least during each subsequent cold start, may either prove or disprove this theory. In any case, the system can't measure the air injection performance EXCEPT during a cold start.

Bottom line - my experience only shows that driving after correcting a condition to remove a readiness flag is not ALWAYS necessary. As the saying goes, "your experience may vary".

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Very well done! Your systematic approach and perseverance paid off.

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Btw, your evap readiness should also set in a few days if you drive both local and highway traffic everyday.

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Yes, the reason is the DME relies on the O2 sensors to detect if fresh air is actually detected at the exhaust during cold start. In this case, one of the sensors is marginal. Bad enough to not reading the O2 correctly during cold start but not bad enough to trip a persistent O2 sensor code.

I also tend to agree with the OP's explanation of why a marginal sensor prevents the SAI readiness from being set.

Well done, and you passed !

So to fix an SAI system rediness-fault , the fix was a post-cat O2 sensor?

Just wanted to close the story because in the beginning this seemed like a very obscure and difficult case.

Edited by Ahsai

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Btw, your evap readiness should also set in a few days if you drive both local and highway traffic everyday.

Thank! Your suggestions were invaluable. I just became a contributing member!

Edited by mesutter

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To JFP in response to: "Last week, we had a 2001 base car in the shop for emissions inspection that finally reset the SAI flag after 87 miles of driving over multiple days. And I've seen cars longer that that as well. It doesn't always work itself out with one run cycle."

Perhaps it has to do with how responsive the post-cat sensors are. If they are old and slower, it may be that the DME just misses getting the info it needs to set the SAI as "ready". After all, they only have about a minute and a half to detect and signal the air pump's oxygen arriving in the manifolds. Did you do a scan on the O2 voltages during cold start on the vehicle that took 87 miles? After changing my right rear, the scan was dramatically different. All of a sudden, the left rear was (noticibly) the laggard, whereas the right had been before.

When the SAI flag is slow, it may not be the miles driven, but the additional cold starts, the final one conveying the DME required info, that leads to the reset. Continous test readiness monitoring while driving, or at least during each subsequent cold start, may either prove or disprove this theory. In any case, the system can't measure the air injection performance EXCEPT during a cold start.

Bottom line - my experience only shows that driving after correcting a condition to remove a readiness flag is not ALWAYS necessary. As the saying goes, "your experience may vary".

 

Yes, we scanned the sensors during cold start, and they were fine.  We always look at the sensor values whenever we scan a customer car, it only takes a few seconds and often heads off a soon to be problem.  The customer also ran a log with his Durametric while the car was away from the shop.  Everything looked fine, but the SAI flag remained until it ran enough miles to satisfy the DME.  As mentioned earlier, from experience 2000-2001 cars seem more prone to do this than other years.

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No conflicts at all the way I see it. John (JFP) said SOME of the cars in those yrs so it doesn't mean all of them will behave the same. John is a pro and a shop owner so I don't doubt his comments/knowledge a bit :)

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No conflicts at all the way I see it. John (JFP) said SOME of the cars in those yrs so it doesn't mean all of them will behave the same. John is a pro and a shop owner so I don't doubt his comments/knowledge a bit :)

Nor did I, sorry if it came across that way. I just wondered if there was any monitoring going on that could help further understand the variation we are seeing between vehicles. The first person that told me that completing the SAI monitoring test could be difficult, before I even started this thread, was a local Porsche dealer mechanic.

If only we could deconstruct the software. However, as the recent VW fiasco shows, even Porsche may not know every line of code that is in there!

Edited by mesutter

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For anyone interested, attached are cold start O2 voltage scans before and after changing sensor B1S2. As is obvious, the blue line is the affected sensor position.

 

Also attached is my smog test results -  PASSED!

 

 

post-104133-0-10581800-1447187281_thumb.

post-104133-0-88166500-1447187298_thumb.

post-104133-0-26094400-1447187314_thumb.

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Very nice. May want to consider changing the other postcat (the red line) sometime as well. Compared to the new sensor, it's quite slow :)

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Yep, and if the SAI monitor had still refused to complete, that would have been the logical next step. I'm going to keep an eye out for good prices on the Internet. For the rear sensor that I just bought, the price from my ususal (and often forum recommended) sources was higher than at the local O'Reilly's (Bosch OEM style).

Edited by mesutter

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I had the same issue with the SAI on '02 Boxster 2.7L. I had 1128, 1130, 0410 and 1410 OBD codes. Fixed almost every things, including hairline crack on the Vacuum reservoir within the SAI system, etc. Basically, the SAI would not reset to readiness even after 2 weeks of driving, with several cold starts, about 450 miles in between, etc. Then the local indy guy, here at San Diego, still found gas smell and found that the fuel sending unit (located under the battery) also had a crack and slight gas was oozing off and the interior would smell nothing but gas. In order to do replace, of course, the battery had to be removed to get to the fuel sending unit. So, the indy tech replaced and put things back together. I drove the car back home from the shop on Thursday, and still the 2A on OBD was flashing, meaning SAI did not achieve readiness status for the CA smog test. I was mad and getting worried about the SAI and the smog test failure and did not drive the car. Then, on the following Monday I started the car in the morning and went to work. I happen to have the OBD reader with me and checked for the code. Every thing was reset and readiness was ok, NO FLASHING 2A on the OBD display! Immediately went for the smog test, and passed. Perhaps, the disconnect from the battery for about a day might have done the trick of clearing the memory containing the codes. That was about a week ago. Yesterday, p1130 code came back with the CEL. On and off, on the tachometer, the needle seem to bounce in between 7 and 9. I am using 91 octane gas. Any one has any idea? Thanks.

Edited by wams

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