The diagnostic fault code did not say to replace the mass air flow sensor. Fault codes never say to replace a part. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part is referenced in a fault code, it is actually the cause of that code about half of the time. First we have to rule out wiring and connector terminal problems, and mechanical problems associated with that part. In this case, there can not be a loose hose clamp or any other leaks that allow air to bypass the mass air flow sensor. Any air that sneaks in without being measured will not be included in the fuel metering calculations.
The first thing you must do is find out the exact fault code number so we can look up the correct description. There are about a dozen codes related to mass air flow sensors, and they mean very different things. Once the code description is known, it may be necessary to watch the sensor's readings on a scanner to see why that code is being set. Your mechanic may also artificially introduce rich and lean conditions to see how the Engine Computer responds.
Dec 2, 2016 at 7:37 AM
