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Old 11-11-2011, 08:23 PM   #1
Registered User
Join Date: Nov 2009
Location: Newport, NC
Posts: 29
My Ride: 2001 330cic
MAF reading question

I have the typical P0174 and P0171 codes. I follow the typical DIY, and get to this point:

How Do I Know if the Problem Is the Mass Air Flow Sensor?
There is a very effective "truth test" for any Mass Air Flow Sensor. Start the engine, let it idle, and then check the Barometric Pressure reading on the scan tool data. If the reading is about 26.5 Hg and you are close to sea level, you know that you have a defective Air Flow Meter because it is telling you that you are at about 4500 feet above sea level. (These conversion tables will help.) When the Mass Air Flow Sensor sees this Barometric reading, it adjusts its Air Density table and then "under reports" the actual amount of air entering the engine. It does this because the Barometric Pressure Sensor is actually part of the Mass Air Flow Sensor.

So, I went to Autozone and used the scan tool, with the following results:

MAF (LB/M) 0.43

MAF (gr/S) 3.22

Since the previous post states: 26.5 Hg, I don't know whether my MAF readings indicate that it is working correctly or needs to be replace. I live near sea level.

Thanks in advance.

ramairbrc is offline   Reply With Quote
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