P0491 p0492 bank 1 bank 2 secondary air injection

[Seal Grey Sasha 986]

Hey guys, I've had secondary air faults for a while now and have more or less been putting diagnosis off. I know there is no electrical fault, as you can hear the pump kick on and off as it's supposed to. My next step would naturally be to smoke test, but I'm seeing a discrepancy in the diagram shown in my Bentley manual and the system in my car. The diagram shows the check valve that is installed in the intake has a single vacuum line that runs to the vacuum canister, however the check valve in my car has a "t" coming off. One line leads to the canister, and the other line leads nowhere. The line is routed over the transmission towards the bank 2 side, and other end is simply open, not connected to anything. I can't seem to find any diagram showing a system with this extra line. Has anyone ever encountered this setup, or has someone done a repair with improper parts? I'm a BMW tech, but my Porsche experience is limited to working on and modifying my own car. Any help would be appreciated...

[78F350]

Sounds like you definitely have a vacuum problem. For more help, we need to know what year your car is and if it has the Tiptronic, or manual transmission.

This thread has a pic of the routing for a manual transmission '01:
http://986forum.com/forums/general-discussions/64576-vacuum-line-clarification.html

[Seal Grey Sasha 986]

My thoughts exactly. My car is a 2003 S with a manual. Thanks for the reply

[78F350]

For the 03, ignore the fuel pressure regulator in this diagram. All the other components need to be connected to vacuum after the check valve. (D, E, F, J, K).
Best to replace all the tubing, otherwise, you'll be back.

[Seal Grey Sasha 986]

Originally Posted by 78F350

For the 03, ignore the fuel pressure regulator in this diagram. All the other components need to be connected to vacuum after the check valve. (D, E, F, J, K).
Best to replace all the tubing, otherwise, you'll be back.

This diagram still doesn't quite explain my predicament though...I see what he says about the tiptronic having a changeover valve...I just had the transmission out of my car for a clutch, but didn't see any kind of valve on the six speed. I assume neither manual has this valve. It seems to me like perhaps a previous owner maybe used junk yard parts from a tiptronic and left the extra vacuum line on? There is an extra line on a t fitting (similar to g in the diagram) that is connected directly to the check valve (h in the diagram). This line is connected to nothing, but just sits open above the transmission. Having an extra line connected to nothing would of course cause an extremely significant vacuum leak. I am assuming someone tried to fix an issue using tiptronic parts and had no true knowledge of how a vacuum system works. I'll try using a different fitting to eliminate this line and see if my MIL will clear. Thank you very much, as this diagram you gave me is far better than anything I have found elsewhere.

[Jamesp]

Here is the schematic for an 03 manual:



There should not be a vacuum line running back to the transmission area, if it is open you have a vacuum leak which can set the SAI code. As you have both codes a vacuum leak can be the culprit. First thing to do is address the loose vacuum hose.


I have a thread asking for professional help (which I was given ) to solve my SAI problem. If you have not read through it you might find useful information there.

Here is where the check valve is on your vehicle:




Use a hand vacuum pump to pull a vacuum on the line connected to the check valve. If it does not hold a vacuum the vacuum resource (#16) may be cracked or a line may be leaking.

While the check valve is out probe the hole that valve sits in to make sure it goes through to the inside of the intake manifold. My SAI was not getting vacuum because I took off the rubber manifold sleeve the check valve sits in, and re-installed it too far over to the left blocking the hole which cuts off the SAI vacuum source.

If that checks out I found that setting the engine to zero timing, and blocking the intake with 3 mil plastic at the throttle body completely seals the intake manifold.

Attach a hose to the intake manifold (I used the fitting just behind the check valve and 5/16 fuel hose) and blow into it. It should hold pressure, if it doesn't you'll need a cheap cigar to blow smoke into the manifold to find the leak.

Do the same with the lower end by taping 3 mil plastic around a hose and the oil fill tube, it should behave the same way.

If all that checks out good, jumpering the relay in the trunk and running the SAI pump with the hose off allows you to make sure it is actually blowing air when it is running.



And if all that checks out,now you are down to the changeover valve, and the shut off valve. You can get to these by removing the alternator. I found that easier than removing half of the intake manifold.

I'd suggest buzzing out the harness for these components before removing them.

Keep us posted on progress -

[Seal Grey Sasha 986]

Found the culprit the other day, and got the car fixed this evening. The vacuum line that was disconnected was the line that was supposed to go to the solenoid for the resonance flap. I had to pick up some parts for a side job I'm doing on a friend's BMW, so I was at the parts store anyway. Grabbed some vacuum line, replaced the lines for the resonance flap, and she's good to go. Just gonna drive her to work tomorrow to confirm the light stays out and smoke it for good measure, but so far, so good.