With Speed Density

Indicates the amount of air passing sensor in grams per second (gm/sec). Normal readings are 4-7 gm/sec. If code 33 or 34 is set, reading will display Engine Control Module (ECM) default value.

NOTE: Vehicles equipped with Speed Density Do Not use the Mass Air Flow (MAF) sensor. There will be no output signal. Test as a 1989 vintage vehicle.