For a few weeks, I've had a CEL and code for the secondary air system in the ZHP.
The code is P0411 - Secondary Air Injection System Incorrect Flow Detected.
I did some basic troubleshooting and discovered that the pump worked and was pushing air into the check valve attached to the exhaust side of the motor.
The valve is suspect, and can often fail. I could not find a real test sequence for the valve; earlier cars (pre 03-2003 production) use a vacuum actuated valve which can be tested quite easily. 03/2003- production cars get a newer redesigned valve that is air pressure actuated.
The secondary air system exists to help the vehicle meet strict emissions standards and to also assist the cats in coming up to temperature more quickly. The system injects fresh air into the exhaust during a cold start for a brief period of time (usually less than 2 minutes). The system should not affect driveability or performance at all; it is strictly an emissions device.
Since the check valve is one of the less expensive parts in the system (around $100) I decided to start by replacing it.
Parts (for 04/2003 production, please check for your application) and tools needed:
11-72-7-553-066 Check Valve
11-72-7-514-860 Gasket
11-72-1-742-644 Self Locking Nuts (2)
10mm socket
Extension
10mm Driver
Pliers
I found it was easiest to remove the washer fluid reservoir, and the secondary air pump so I could more easily access the check valve.
The picture below was after I had removed those components:
Drain the reservoir first!
The washer reservoir will have up to 3 electrical connections - one for the level sensor, one for the headlight washer pump, and one for the windshield washer pump.
Disconnect and remove those from the washer fluid reservoir.
With those connections removed, there's one 10mm bolt holding the reservoir in place.
Remove it and the whole reservoir should come out - it may take a bit of wrangling.
In the picture above, the check valve is the UFO looking silver thing in the center of the picture.
Next, I removed the secondary air pump; there's 3 10mm bolts holding it in place. Once those are removed, there's an electrical connection on the bottom.
Remove the two hoses connected to the pump (the hoses are press-fit with plastic collars - use a small screwdriver on the big hose on top of the pump).
The pump then will lift right out of its bracket.
Closeup of the valve and hose:
Secondary air pump removed, and the new check valve from BMW:
I found it easier to disconnect the hose from the check valve after it was removed from the car.
The valve is held onto the exhaust manifold by 2 10mm nuts.
I recommend having replacements handy since these are copper and will deform and/or "weld" themselves to the block.
This picture shows the valve removed along with its gasket:
Here's some comparison shots of the old versus new valve:
Assembly is, as they say, reverse of disassembly.
I reinstalled the check valve, then the secondary air pump, then the hoses, and then the washer reservoir.
It'll take a couple of drive cycles to know if this fixes the problem - I'll report back the results.
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