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Smog Purgatory on 2002 Boxster S

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Hello fellow BoxsterFarians.  I am stuck in Smog purgatory.  Of the 5 "ready" attributes one will not come ready (which prevents California smog stations from being able to run a smog test).  The attribute that is giving me trouble is the Secondary Air System test.  When I started on this journey I had a few CEL codes that needed to be dealt with.  I was throwing P0410 and P0411 as well as P1128 and P1130's.  To add some excitement I was also getting P1115 codes occasionally.  I tackled the P1115 error first.  (Durametric translation - Porsche fault code 13 Heating Power O2S ahead of cat c bank 1).  I swapped the two front (ahead) O2 sensors and drove it around a bit.  Soon I had a similar error but it pointed to bank 2.  So the error followed the sensor.  I replaced that O2 sensor and the P1115 error is gone.  Next was the P1128 and P1130 errors.  Everything I read pointed to the Mass Airflow Sensor.  Swapped that out, now all my errors are gone.  Ready for Smog test right ?   Well not so fast...  Once the CEL codes are cleared, all 5 smog ready attributes change to the FAIL state.  In order for the attributes to transition back to the PASS state one must drive the car through a cycle.  There are tons of forum postings on what makes up a drive cycle so I won't go into that here. Long story short - I have driven through 4 controlled drive cycles and that pesky Secondary Air attribute will not change to pass.  I have no other codes showing and things seem to be stuck.  Some postings indicate that a weak O2 sensor can prevent the Secondary test from running to completion leaving one in Smog Purgatory.   I have attached a Durametric log graph from my latest coldstart.  (My Secondary Air pump appears to run fine and turns off after 60 seconds or so).  If you look at the graph, the O2 sensor voltage AHEAD of cat (Bank 1 and Bank 2) appear to react differently during the time the air pump is running. Bank 1 (RED Graph) is the new O2 sensor.  Bank 2 (BLUE Graph) is an O2 sensor that has not been changed.  Should these two sensors track more closely? (as the two AFTER cat ones do ?)  Could this difference in O2 Sensor performance be a cause of my Secondary Air test never finishing ?  Would love to hear some opinions from this forum. Thank you, Frankyzambony Livermore California.


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I think you are correct the red line is part of the reason your SAI readiness is not set. I see two issues from the plots:

1) the spike on both pre-cat sensor at the early stage. Since both sensors read the same spike, that tells me you have problems in the changeover valve and/or the SAI combo valve. Could be some sticky or clogged valves.

2) the red line does not stay low enough meaning there's not enough O2 detected on bank 1. Your SAI passages in bank 1 could be partially clogged by carbon. Do you have lots of miles on the engine?

For the SAI readiness to set, both the red and blue lines need to stay low for the first 60s or so (other than the first 10s where the sensirs are not hot enough to read anything yet). A normal plot is shown in post #47 here http://www.renntech.org/forums/topic/49155-secondary-air-test-readiness-monitor-incomplete/page-3

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John owns a shop so he sees many cars. I would listen to him.

Now onto trouble shooting. If you have a hand vacuum/pressure pump, it's quite doable. There are a few things to check:

1) The SAI pump itself. Remove its air hose and feel for a strong stream of air at cold start when it's activated. The rest are performed with engine off.

2) Unplug #22 from the intake and hook up the vacuum pump to it. Start pumping until you see vacuum. It will take many strokes as the vacuum being stored in the vacuum reservoir #16. Check if the vacuum holds for 20min or so.

3) If vacuum does not hold, you need to unplug individual components and check them one by one using the vacuum pump, #15, 16, and 18. The vacuum reservoir is known to leak and to check it thouroughly, you need to remove it, spray the bottom with soapy water and apply a few PSI to it to check for bubbles.

4) If everything checks out, I would remove #15 and bench test it to make sure the air way is not blocked when vacuum is applied and air is forced into it.

5) You can also use a 9v battery to verify the operation of the changeover valve.

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Also keep in mind the vacuum lines 25, 26, and 27 could be brittle so handle them with care. Also pick the disconnect points wisely so your vacuum tests also include testing those lines. It's not a bad idea to replace those lines while you're there ~$10/meter from the dealer.

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Your bank 2 cat may be weak. In general on a fully warmed idling engine, the post cat sensor should stay at around 0.7v more or less constant. The pre cat sensors will swing between 0.1 to 0.8 about once a second. You may want to generate another plot for a fully warmed up idling engine. Regardless, this is orthogonal to the SAI issue.

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Happy new year ! 


So I went outside this morning to get one more record of the coldstart and to my surprise the ready status had finally flipped.


(4 controlled drive cycles plus 1 short drive cycle last night of < 3 miles)


Attached are the logs from this latest startup, things look much better however I have not changed a thing.


The good news is I will be heading to the SmogMan tomorrow and hopefully will pass Smog.


Thanks to everyone that chimed in for help...





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