|02-08-2014, 09:51 PM||#1|
Join Date: Jan 2014
Location: Milwaukee, WI
My Ride: 2004 330Cic ZHP
SAP Troubleshooting Guide - P0411 - Newer SAP with MAF sensor
So - I was getting a P0411 code on my 2004 330ci vert for an SAP airflow issue. I found lots of information on troubleshooting the old style SAP system with the vacuum check valve, but not so much on the newer style with the MAF sensor and check valve without the vacuum. I started with a post from JFOJ and added some additional troubleshooting steps,
Check all hoses for blockages.
Pop center hose on air pump and spin pump with finger - pump is not tight or frozen, no prior noise from pump. If pump is frozen or noisy, replace the pump. Swapping the pump is very easy, but expensive. Hope that's not your problem.
The SAP only runs on a cold start. Start car cold with hood open and listen for pump to run, put a hand on it to feel it run. If the pump doesn't run at all, check the fuse, relay, and wiring. If the pump runs, but stops after 5 to 10 seconds, then it's either the MAF or check valve. The MAF itself can fail or if the check valve fails (closed), the MAF will sense the lack of air flow and shut off the pump.
There's a lot of posts that said that you can't test the new check valve, but that is not correct. You can actually test the check valve by blowing into it (a good hard puff will go thru). If it's frozen, you will not be able to get air thru it. I am guessing if you want, you could remove the outlet hose on the pump and blow into it. I removed mine from the car to test it. If you can't get a strong puff of air thru the valve, replace the check valve. The valve is about $100 and is pretty simply to replace.
If everything else checks out, replace the SAP MAF. I don't know anyway to test this, but you've pretty much eliminated everything else. The MAF is also very easy to replace and runs about $65. See the other link below on replacing that.
Here's a few links for more info:
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