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Sam, BMW Master technician
Category: BMW
Satisfied Customers: 1043
Experience:  BMW S.T.E.P. graduate, 10 years BMW dealership experience
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2003 BMW 325i: my Service Engine Soon light is on..Secondary Air..flow

Resolved Question:

I have a 2003 BMW 325i and my Service Engine Soon light is on. Pulled the codes and I have P0491 and P0492. I've done my research and I know it's the Secondary Air Injection System: Insufficient flow bank 1 and bank 2. Is this something I can fix myself? If so where can I find parts?
Submitted: 7 years ago.
Category: BMW
Expert:  Sam replied 7 years ago.
Hello and welcome to Just Answer.

The most common failiure in this system is the vacuum line to the non-return valve. The vacuum line at the valve will get very brittle and break. The valve is on the front of the engine on the exhaust side of the head. The hose will be visible toward the rear of the valve.
Customer: replied 7 years ago.
Is there a website or auto parts store where I can find a replacement?
Expert:  Sam replied 7 years ago.
The vacuum hose in that spot is nothing special, just regular vacuum hose.

Can you check the hose first and tell me the condition?
Customer: replied 7 years ago.
There seems to be 2 hoses. One large short hose which goes to the air pump and a small hose in the back that I can't tell where it goes to but both hoses seem to be in good condition.
Expert:  Sam replied 7 years ago.
The smaller hose is the vacuum line I am refering to. If the hose is ok there can be several things that can cause these faults. With the whether starting to cool down the non-return valves will sometimes stick closed and block the flow,

The only way to properly diagnose the system is to test it using a scan tool. You can ask a shop to diagnose the faults without repairing the problem. The shop should not charge more than an hour labor to diagnose the faults as secondary air faults are pretty common.
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