4wd circuit, without electronic shift control, with heavy duty transmissio for GMC Pickup K2500 (1985-2000)

AUXILIARY BATTERY RELAY BLK WIRE BLK/WHT WIRE BRN WIRE DIESEL FRONT AXLE ACTUATOR FUSE 24 GASOLINE GRY WIRE GRY/BLK WIRE HARN) HOT IN PARK OR HEAD HOT IN RUN I/P FUSE BLOCK (LEFT SIDE OF DASH, ILLUM FUSE 14 INDICATOR LT BLU WIRE M/T A/T POWERTRAIN CONTROL MODULE (BEHIND RIGHT RED WIRE SIDE OF DASH) TIMER LOGIC, RELAY MODULE (RIGHT SIDE OF FIREWALL) TRANSFER CASE MODE SELECTOR ILLUMINATION LAMP TRANSFER CASE SYNCHRONIZER (TOP OF TRANSFER CASE) VEHICLE CONTROL MODULE (LEFT SIDE OF ENGINE COMPT)