Overdrive Switch: Testing and Inspection
46RE - AUTOMATIC TRANSMISSIONOVERDRIVE ELECTRICAL CONTROLS
The overdrive off switch, valve body solenoid, case connectors and related wiring can all be tested with a 12 volt test lamp or a volt/ohmmeter.
Check continuity of each component when diagnosis indicates this is necessary.
Switch and solenoid continuity should be checked whenever the transmission fails to shift into fourth gear range.