1997 gmc safari

i have a 1997 gmc safari van. the check engine light is staying on. the codes i'm getting are 102,103,172,175. i've changed the mass air flow sensor twice and the problem persists. the van has 224,000 miles on it but it runs great. no excessive fuel consumption,(19-21mpg.) runs smoothly, no skipping or stalling. the scanner says i have low voltage to the mass air flow sensor but i changed it and it does not make a difference. the 02 sensors are original but the scanner says that they are working fine. any help would be greatly appreciated. thanks.

If the trouble code reference number, tells you that you have low voltage going to MAF sensor, would that not mean that your PCM ( computer) is not supplying the 5 volt required for the sensor. Maybe you should measure the voltage going to the sensor, and if it is low check you PCM for bad grounds. Just a thought.