Service Manual Section 8A, 1988 and 1989 Pontiac and Buick W-car page 33-2.
The voltage measurement in Vehicle Speed Sensor Test A should read as follows:
Measure Correct For Between Voltage Diagnosis ------- ------- --------- C8 (YEL) and Varying from Seel C2 (PPL) 0.1 to 0.5 volts AC
Please correct your Service Manuals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.