Exactly what code was stored causing the MIL to come on? Where there any other stored or pending codes? Did the tech graph or measure the MAF output voltage?
The MAF sensor has an output voltage of 0 - 5 vdc which goes to the ECM. Typical idle reading will be .6 to .9 vdc and this voltage will increase with greater airflow(higher rpm & higher load) up to a realistic limit of about 4.5 vdc at full throttle, though this would not be normal driving conditions - I hope. You can check this voltage with a voltmeter. right at the MAF connector if you can identify and access the correct pins on the connector. A voltage LOWER than .45 at idle will set a code, as will any self-checks done through some resistive bypass circuitry built in to the MAF. The MAF circuit basically looks at how much current is necessary to maintain constant temperature in a small heated wire in the presence of a small portion(slipstream) of the intake air. The MAF has a thermistor temp sensor that works in conjuntion with the heater wire. This ECM flow measurement loop also uses the voltage output from the IAT sensor(Intake Air Temperature) in its calculations.
http://www.gatewaycleanair.com/mecha...4/dirtymaf.htm