For electronic units following are basic tests from indicator lights.
Air bag
When you put ignition key to ON position, air bag warning light illuminates for about 7 seconds and then turns off. It indicates the unit is operational.
Following indicates a fault in the unit
The light remain on after proximately 7 seconds
Light flashes very quickly
Light doesn't come on at all
Light turns on when driving
ABS
When you put ignition key to ON position, ABS warning light illuminates for about 1 seconds and then turns off. It indicates the unit is operational.
If the light doesn't come on at all or if it flashes during driving means a fault.
Automatic Transmission
When you put ignition key to ON position, OD-OFF warning light should illuminates for about 2 seconds and then turns off.
If the light doesn't come on at all or if it flashes during driving means a fault.
Please note that we can't guarantee that the units are 100% operational by those lights. But if the above tests fails, it indicates a fault in units.