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Old 01-13-2015, 08:52 AM   #1
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Help diagnosing possible SAI problem.

I've been getting regular (about every 2 weeks or so) CEL for the SAI system P 0410 "signal implausible" as well as 1128 and 1130 which indicate the fuel trims are at full rich. The MAF is reading lowish, around 10-11 when it should be at 15. This leads me to believe that I am getting a vacuum leak somewhere in the SAI system.

Does that sound right and if there is a vavuum leak from the SAI, what are the usual suspects?
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Old 01-14-2015, 03:50 AM   #2
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The SAI terminates onto the manifold with a small black & white check valve. That valve can just slip out and be not connected. Then you don't get SAI, and there is an open hole on the manifold. Or, follow the tubing.
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Old 01-14-2015, 07:50 AM   #3
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There is a troubleshooting flow chart in this thread that might be helpful - start with the air pump and go from there.

One thing of slight interest is that only Bank 1 is throwing the code (you don't have a P0411 for the other side), so in the back of your mind pay particular attention to components isolated to Bank 1 while going through the troubleshooting process.

The SAI system can be somewhat problematic to troubleshoot and diagnose as the codes are somewhat general and there is a large number of components that could be the problem. Good luck.

P0410 and P1411 - Running Out of Ideas - 986 Series (Boxster, Boxster S) - RennTech.org Forums
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Last edited by thstone; 01-14-2015 at 07:54 AM.
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Old 01-15-2015, 07:06 AM   #4
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It did throw the code for both banks,I just forgot to list it. Thanks for the flowchart.
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Old 01-15-2015, 08:01 AM   #5
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there is a vacuum line to the sai system. here's a diagram of the vacuum lines:





L and B are the two boots on your intake system that join the plenum to the manifold - this is where the vacuum comes from (there is also a vacuum line for the brake booster that comes direct off the intake manifold, and a vacuum line for the aos on the upstream side of the throttle body).

B feeds the fuel pressure regulator (C).
L feeds a one-way valve (H) then charges the vacuum tank (F).
Vacuum is provided to J/K which is the resonance flapper control (J is an electric valve that, upon signal from the ecu, sends vacuum to K which activates the flapper).
Vacuum is also sent to another electric valve (E) which is tied to the SAI system (D).

there are a couple of 'T' fittings in the system - G and I. you'll note that there is an untapped branch on I - I can't remember where it goes to, or if it is blanked (I have a post on here someplace from when I did remember what it did ...).

so, a vacuum leak in this system can affect fuelling (either through incorrect air readings or improper operation of the resonance flapper) and affect the SAI.

Last edited by The Radium King; 01-15-2015 at 08:12 AM.
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Old 01-17-2015, 07:11 AM   #6
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Sai

Radium King,

Thank you for posting the diagram with the explanation of where the vacuum hoses go, Could you please describe the function of the SAI..?

I am planning on removing the intake manifolds to clean the engine and ensure that all the vacuum lines are properly connected, since a few years ago I installed the IPD performance plenum with the larger throttle body and one of the vacuum lines are supposed to be capped out (I want to ensure that remains capped), at the same time I will clean the mess made by the failing AOS…

I am not sure what I have to do to keep your diagram handy for later reference, thanks again!

Last edited by Gilles; 01-17-2015 at 07:17 AM.
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