If it is also dead on highest
speed it is likely something other than the Control Module, which is used to slow the motor from high speed. It should get bypassed in HIGH.
The ground for the motor (and the blower control mod.) is via the passenger front fender above the battery. Take that loose and clean the ends of all the black wires.
If your ECC is the same as my 93, the other common item is the dashboard HVAC control panel (yuk).
My schematic also shows fuse 17 (25 amp) as being a common requirement for all blower speeds. This is in the fuse block under the dash near the steering column.
If it runs on some speeds but not others, it will point towards something else. So knowing that is important.
Again, all I have is manual for a 93, so just crossing my fingers that the items above are common to your year.