RAM 4500 Chassis Cab Truck 2WD L6-6.7L DSL Turbo (2008)
Overdrive Switch: Testing and Inspection
DIAGNOSIS AND TESTING - OVERDRIVE ELECTRICAL CONTROLS
The tow/haul 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.