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Old 01-28-2013, 01:11 PM
Richey Richey is offline
Registered User
Location: Indianapolis
Join Date: Apr 2008
Posts: 34
Mein Auto: 2001 530i 230k+ miles
Secondary Air System Issues

I got an SES with codes P0491 & P0492 (Secondary Air System). I took it to a local shop that I've used before and somewhat trust to diagnose this and fix some other minor things that I didn't have the time to do.
Verdict: bad air pump. It was getting power; just not working. Fix: New Air Pump.

3 Days later, SES light with same codes. I verified the air pump was running...I heard it running. I had searched the forum and put my money on a bad air check valve. I ordered one and installed it myself. The vacuum hose from the air check valve to the solid plastic hose running along the side of the engine looked ok so I didn't replace it. Cleared the codes.

2 Days later, SES light with same codes. I climbed in the engine compartment and replaced two of the back vacuum hoses. They did seem pretty brittle. Hopefully this was it.

2 Days later the light came back on. Dammit man!

My question is: while I had the hose of the air check valve, I blew into it and air came out from behind the engine. This is before I replaced the back hoses so I thought it was obvious I had a leak. After replacing the hoses, I could still do this. Is this right? Should the system be closed or does the electric check valve keep the system open until it gets a signal to close the system to create the vacuum to open the air check valve?

The electric valve is about all I have left to replace unless the system is working and a sensor went bad. Or I got a faulty air check valve...I really hate when new parts don't work.

Thanks in advance for any help.
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