P0491 p0492 bank 1 bank 2 secondary air injection

[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.