You can't test a hall sensor with a voltmeter with it disconnected. A HALL sensor needs voltage in to get pulses out. The manual tells how to use an oscilloscope to test it. What the manuals don't tell you is: on 1988 and later cars you can scope the diagnosis connection on pin 9. The diagnosis connector on 1987 cars says "factory only". If you have a diagnosis connector on your car, scope it. I tried disconnecting it with the engine running at idle and there was no effect. The manual says that it will retard the spark if the hall sensor is failing, but that is probably under load and not idling. I find that very interesting. How does it know when to spark with the hall sensor failing?
Earl Gillstrom '88 5 speed 101,000 miles 279hp 305 ftlb with 106F ambient.