D150 1/2 Ton Pickup 2WD V6-239 3.9L VIN X FI (1988)
Speed Control Switch: Testing and Inspection
Fig. 6 Speed Control Continuity Chart. 1988-90 Rear Wheel Drive Models
Fig. 7 Speed Control Continuity Chart. 1988-90 Front Wheel Drive Models
Fig. 8 Speed Control Connector Terminal Identification