The Selector Lever is not in Position P or N.

Place the Selector Lever in Position N.

The Selector Lever Position Switch/Shift Linkage adjustment is incorrect.

Adjust the Selector Lever Position Switch/Shift Linkage.

The Fluid Pump is blocked.

1. Remove the Pump.
2. Clean and repair the Pump as necessary.

The Torque Converter is blocked.

1. Remove the Converter.
2. Repair or replace the Converter as necessary.