AMM Troubleshooting -- Have a Known-Good Spare
Armed with the wiring diagram, how does one diagnose the MAF circuit??
About all you can do with a multimeter is check for some very basic faults in the wiring, and some not very common faults in the AMM itself. I prefer calling the Bosch hot wire air mass meters AMMs and leave the GM terminology "Mass Air Flow" sensors to the later film-based units. The resistance check is a lame attempt by Volvo's early tech writers to check for a broken wire. In actuality, there's a temperature-dependent resistor across those terminals which ordinarily reads within the specification given for both together, so, unless you're using rather sophisticated resistance measuring equipment, the "ohm check" is useless. Just look at the wire.
Most LH2.4 air mass meters fail just out of range of the adaptive capability of the ECU, when they fail, whether from overcooked electronics (the airbox tstat culprit) or from heavily contaminated platinum. My opinion is that a certain number of Air Mass Meters are put in their graves by enthusiasts wielding cans of "Mass Air Flow Sensor Cleaner" or so it seems reading the stories here and elsewhere.
So what can you do with a wiring diagram and a multimeter? You can prove one either suspect or bad, but
you can't prove one good.
Check the output voltage at rest -- that's the white/red wire. Turn the ignition key to KP-II without starting the motor. Slip the boot back and probe the rear of the connector. Measure the voltage from the negative battery post to the white/red wire. While doing so, also check to be sure the black/brown wire has a good connection to ground as evidenced by less than 200mV on the plug pin. And like the OP did, make sure the battery power is good at the orange wire (1991) or red/black (92-93).
I like to see the output of the AMM at white/red above 1.400V, with no air movement. Yes, I've seen them working well even down into the high 1.290's, but with some ECUs and not others. This is hairy edge territory in my opinion. Make sure the hot wire responds by tweaking the corrugated hose a tad to see the meter fluctuate upward. No need to disassemble the plumbing.
You can start the car and see how the output responds to the throttle and where it is during idle, but the airflow/temp conditions vary so much, there's no number you can assign that will discriminate between a good and bad unit in all cars. The response is non-linear.
But bottom line, the only definitive proof, without a temperature controlled flow bench, is to substitute a known-good unit. My advice for 20 years has been to acquire at least one good spare before it is needed and keep it on hand for troubleshooting. Junkyard AMM with a day spent in your car is good insurance.