The pump is controlled by the engine computer (DME in BMWspeak). The DME uses the data from the engine temperature sensor located in the cylinder head between cylinders 5 and 6 to determine when to activate and deactivate the secondary air pump (SAP). Now, the emissions monitors need to go through several drive cycles before the various monitors are good to go. Google “BMW emissions drive cycle.”

 

I am well aware of the drive cycles I just can't figure out why once in awhile the light turns on at shutdown

 

You need to determine what the code is when the light comes on. Put a scanner on it and retrieve the code and start from there. Without a code description you will never know where to start.

 

The air pump always seems to trigger it before I could get enough drive cycles in. Usually when it's really cold out it's fine with cold starts when it is warmer out or the car is warm is when I get the air pump code

 

I replaced my bad air pump along with the automatic valve on my 04 e46 m54. Unfortunately, I need to get it through emissions by the end of January. I had this car since n'ew, and was just giving it to my son who got his license yesterday. The ses light will stay off for a while, but sometimes will come back on just as the air pump cycles off on a cold start. I have cleaned the airflow sensor.

I really could care less about the light for that, but I just need to get through emissions here in Maryland. I had the light off for a week, but still showed as "not ready" at emissions.

Any clue why the air pump triggers at shut down?

I just went through this with my 06 325ci. In my case the light came on after the pump turned off. I cleared the code and SES lite, Then I disconnected the output hose at the pump. Next start - pump came on, turned off after the same run-time as the previous start - and no lite or code. The pump was moving a lot of air. My guess was the MAF is reporting either 'sufficient' or 'insufficient' air flow. The pump run-time appears to be affected by head temp. This sequence suggested either the valve was not opening or the passages in the head were restricting the airflow. I repeated this several days in a row - driving around with the hose left disconnected.

On a e60 v8 forum dirty passages are reported as common and the dealers want 6 grand to pull the heads and clean them. That engine has an oil consumption problem. I resorted to one of their work arounds to clean the heads.

On my E46 I resorted to 'mechanic in a can' - Seafoam - as a diagnostic aid. Prior to the first start of the morning disconnect the pump output hose at the pump - fill it with seafoam - reconnect it - then start the engine. After a short time you should see white smoke out the tail pipe. In my case I didn't - and the SES lite and code set. Either the valve wasn't opening or the passages were plugged. I shut the engine off and let it sit for the day. After several iterations of this a big white cloud appeared out the tail pipe and it has functioned normally since then. If It had indicated normal operation on the first start I would have suspected the MAF.

In a locality that requires emissions testing you really want this system to work. One of its functions is to extend the service life of the catalytic converters.

 

Way cool, the little fixes that get shared here.

Great job!

 

Thank you! I will definitely try that. I replaced the pump and valve at the same time. Valve from dealer, and pump aftermarket. As I said, the pump cycles the way it should, just every once in a while as soon as it shuts off, the light comes on for secondary air injection.

 

Btw, since I have the automatic valve, not the vacuum one, it wont open unless air pushes it. So putting the seafoam in without connecting the pump hose, it will never go inside.

 

Thats why you reconnect the hose - after you fill it with seafoam - and before you start the engine.

 

I realized I missed that part. I already picked up the seafoam, and will probably try that tomorrow.

 

I tried the seafoam this morning. It all seemed to leak out at the bottom of the hose at the valve. I'll have to take it off later and see what's up with it. Any chance a leak in that hose could cause the code?

 

Any chance a leak in that hose could cause the code?

I don' t know for sure. But it will keep the system from working the way it is intended. It should be repaired.

is this seafoam trick a good way to clean the catalytic converters?

I'm not an expert on catalytic converters. I know they will 'deplete' eventually and that unburned fuel shortens their life. Whether that process 'clogs' them or increases back pressure I don't know. If you have oil burner I don't know how that affects cats.

 

I kept ruling out the check valve because it was new and from the dealer. When I couldn't get any evidence of the seafoam burning in the exhaust, I removed the valve to find it rusted and frozen shut again. I put it all back together and just left the hose off of the air pump output so I dont get another bad pump due to the same reason.

 

It took 3 days and 3 iterations of this to get mine to work. I still don't know if it was the valve or the passages in the head that were blocked. Out of curiosity - how did you determine your new valve is 'frozen shut'? I don't know what this valve is. Although there is not that much pressure from the exhaust ports on the valve I would think there is some significant mechanical force holding it closed.

 

No air was passing through to the exhaust. I took the check valve off and looked inside and saw how rusty it was. I filled it with penetrating oil and soaked it for a bit, then connected the blow side of my shop vac to it, and the valve was frozen shut tight.

 

Update:

I left the frozen air pump valve, and just disconnected the hose from the air pump. 2 weeks no ses light, and it passed state emissions.