GMC Pickup C2500 (1985-2000) transfer case switch Wiring diagrams

1-2 SHIFT SOL 2-3 SHIFT SOL 3-2 SHIFT SOL TRANS FLUID TEMP (TFT) SENSOR 999 998 961 452 389 995 PPL ACCELERATOR PEDAL POSITION (APP) MODULE (TOP OF ACCEL- ERATOR BRACKET) APP #3 APP #3 SENSOR SIG APP 1 APP 2 BLK WIRE BLK/WHT WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE DATA LINK CONNECTOR (BELOW LEFT SIDE OF DASH) DK BLU WIRE DK GRN WIRE ECM I FUSE ECM-B FUSE ENGINE COOLANT TEMPERATURE (ECT) SENSOR (LEFT LOWER FRONT OF ENGINE BLOCK) GAUGES FUSE GRY WIRE HOT AT ALL TIMES HOT IN RUN OR START HOT IN RUN, BULB TEST OR START I/P FUSE BLOCK INSTRUMENT CLUSTER LT BLU WIRE LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE ORG/ WIRE PNK IGNITION FEED 3-2 CONTROL SOL DIAGNOSTIC REQUEST WIRE PNK WIRE POWERTRAIN CONTROL MODULE (UNDER RIGHT SIDE OF DASH) PPL PPL TCC/BRAKE SW PPL/WHT WIRE PRESSURE CONTROL SOLENOID RANGE MODE SELECTOR RED WIRE RED/BLK WIRE SERVICE ENGINE SOON SPEED SENSOR (LEFT REAR SIDE OF TRANSMISSION) STOP/HAZ FUSE 1 TAN WIRE TAN/BLK WIRE TCC PWM SOL TCC SOL TCC/STOP LAMP SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) TRANS FUSE 20 TRANSFER CASE SWITCH TRANSMISSION UNDERHOOD FUSE/RELAY CENTER VEHICLE SPEED SENSOR BUFFER (UNDER RIGHT END OF DASH) WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

1-2 SHIFT SOL TCC SOL 2-3 SHIFT SOL 3-2 SHIFT SOL 999 998 961 452 1586 995 PPL ACCELERATOR PEDAL POSITION (APP) MODULE (TOP OF ACCE- LERATOR BRACKET) APP #3 APP #3 SENSOR SIG APP 1 BLK WIRE BLK/WHT WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE DATA LINK CONNECTOR (BELOW LEFT SIDE OF I/P) DK BLU WIRE DK GRN WIRE ECM IGN FUSE ELECTRONIC 4-SPEED AUTOMATIC OVERDRIVE TRANSMISSION ENGINE COOLANT TEMPERATURE (ECT) SENSOR (RIGHT SIDE OF ENGINE) FUSIBLE LINK GRY WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START HOT IN START OR RUN FUSE BLOCK TRANS FUSE IGNITION FEED 3-2 CONTROL SOL DIAGNOSTIC REQUEST LT BLU WIRE LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE ORG/ WIRE ORG/BLK WIRE PNK WIRE PNK/BLK WIRE POWERTRAIN CONTROL MODULE PPL PPL APP #2 PPL TCC/BRAKE SW PPL/WHT WIRE PRESSURE CONTROL SOLENOID RANGE MODE SELECTOR RED WIRE RED/BLK WIRE SPEED SENSOR (LEFT REAR SIDE OF TRANSMISSION) TAN WIRE TAN/BLK WIRE TCC/ BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) TRANS FLUID TEMP (TFT) SENSOR TRANSFER CASE SWITCH VEHICLE SPEED SENSOR BUFFER (UNDER RIGHT END OF I/P) WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

1-2 SHIFT SOL ACCELERATOR PEDAL POSITION (APP) MODULE (TOP OF ACCE- LERATOR BRACKET) APP #3 APP #3 SENSOR SIG APP 1 BLK WIRE BLK/WHT WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE DATA LINK CONNECTOR (BELOW LEFT SIDE OF I/P) DK BLU WIRE DK BLU/WHT WIRE DK GRN WIRE ECM IGN FUSE ELECTRONIC 4-SPEED AUTOMATIC OVERDRIVE TRANSMISSION ENGINE COOLANT TEMPERATURE (ECT) SENSOR (RIGHT SIDE OF ENGINE) FUSIBLE LINK GRY WIRE GRY/RED WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START HOT IN START OR RUN FUSE BLOCK TRANS FUSE IGNITION FEED TCC DIAGNOSTIC REQUEST LT BLU WIRE LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE ORG/ WIRE ORG/BLK WIRE PNK WIRE PNK/BLK WIRE POWERTRAIN CONTROL MODULE PPL PPL APP #2 PPL TCC/BRAKE SW PPL/WHT WIRE PRESSURE CONTROL SOLENOID RANGE MODE SELECTOR RED WIRE RED/BLK WIRE SPEED SENSOR (LEFT REAR SIDE OF TRANSMISSION) TAN WIRE TCC SOL 2-3 SHIFT SOL TCC/ BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) TRANS FLUID TEMP (TFT) SENSOR TRANS INPUT SPD SIG LO TRANSFER CASE SWITCH TRANSMISSION INPUT SPEED SENSOR (LEFT SIDE OF TRANSMISSION) VEHICLE SPEED SENSOR BUFFER (UNDER RIGHT END OF I/P) WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

AUDIO ALARM MODULE (ON CONVENIENCE CENTER) AUTOMATIC TRANSFER CASE CONTROL SWITCH (LUXURY) AUTOMATIC TRANSFER CASH SELECT SWITCH AUXILIARY HEATER CONTROL BASE BLK WIRE CARGO LAMP SWITCH (PICKUP ONLY) TRANSFER CASE SWITCH CONVEN- IENCE CENTER DAYTIME RUNNING LAMP (DRL)/ RADIO OVERRIDE SWITCH DAYTIME RUNNING LAMPS (DRL)/ RADIO OVERRIDE SWITCH DISPLAY DIM SIG DISPLAY DISPLAY DIM DIM SIG SIG FOG LAMP SWITCH FRONT AUXILIARY HVAC CONTROL LAMP GRN WIRE GRY WIRE HEADLAMP, PANEL DIMMER SWITCH HOT AT ALL TIMES HVAC CONTROL LAMP I/P FUSE BLOCK ILLUM FUSE 14 ILLUMINATION INFLATABLE RESTAINT I/P MODULE SWITCH INSTRUMENT CLUSTER LIFTGATE RELEASE SWITCH (SUBUR- BAN/ UTILITIY ONLY) LUXURY OFF ORG/ WIRE PARADE MODE SW PARK PARK LPS FUSE 9 PICKUP/ EXTENDED CAB ONLY PPL PPL PPL RADIO RADIO INFLATABLE RESTAINT I/P MODULE SWITCH REAR AUXILIARY HVAC CONTROL LAMP REAR AUXILIARY HVAC CONTROL SWITCH REAR WINDOW WIPER/ WASHER SWITCH RHEO- STAT SUBURBAN, UTILITY ONLY SWITCH (SUBUR- BAN/ UTILITIY ONLY) TRANSFER CASE SHIFT ILLUMINATION LAMP TRANSFER CASE SWITCH WHT WIRE

AUDIO ALARM MODULE (ON CONVENIENCE CENTER) AUTOMATIC TRANSFER CASE CONTROL SWITCH (LUXURY) AUTOMATIC TRANSFER CASH SELECT SWITCH AUXILIARY HEATER CONTROL BASE BLK WIRE CARGO LAMP SWITCH (PICKUP ONLY) TRANSFER CASE SWITCH CONVEN- IENCE CENTER DAYTIME RUNNING LAMP (DRL)/ RADIO OVERRIDE SWITCH DAYTIME RUNNING LAMPS (DRL)/ RADIO OVERRIDE SWITCH DISPLAY DIM SIG DISPLAY DISPLAY DIM DIM SIG SIG FOG LAMP SWITCH FRONT AUXILIARY HVAC CONTROL LAMP GRN WIRE GRY WIRE HEADLAMP, PANEL DIMMER SWITCH HOT AT ALL TIMES HVAC CONTROL LAMP I/P FUSE BLOCK ILLUM FUSE 14 ILLUMINATION INFLATABLE RESTAINT I/P MODULE SWITCH INSTRUMENT CLUSTER LIFTGATE RELEASE SWITCH (SUBUR- BAN/ UTILITIY ONLY) LUXURY OFF ORG/ WIRE PARADE MODE SW PARK PARK LPS FUSE 9 PICKUP/ EXTENDED CAB ONLY PPL PPL PPL RADIO RADIO INFLATABLE RESTAINT I/P MODULE SWITCH REAR AUXILIARY HVAC CONTROL LAMP REAR AUXILIARY HVAC CONTROL SWITCH REAR WINDOW WIPER/ WASHER SWITCH RHEO- STAT SUBURBAN, UTILITY ONLY SWITCH (SUBUR- BAN/ UTILITIY ONLY) TRANSFER CASE SHIFT ILLUMINATION LAMP TRANSFER CASE SWITCH WHT WIRE

A/C CLUTCH RELAY A/C CONTROL MODULE ANTILOCK BRAKE MODULE AUXILLIARY AUXILLIARY HEATER-A/C HEATER-A/C REAR LOGIC CONTROL MODULE AUXILLIARY HEATER-A/C FRONT CONTROL BLU WIRE BRAKE FUSE BRN WIRE BRN/WHT WIRE CONVENIENCE CENTER DK BLU WIRE DK GRN WIRE ELECTRONIC TRANSMISSION 4-SPEED AUTOMATIC W/OVERDRIVE FUSE FUSE BLOCK FUSIBLE LINK GLOW PLUG CONTROL MODULE GLOW PLUG FUSE GRY WIRE HEATER BLOWER SWITCH HEAVY DUTY ELECTRONIC TRANSMISSION 4-SPEED AUTOMATIC W/OVERDRIVE HIGH BLOWER RELAY HTR A/C FUSE IGNITION SWITCH INSTRUMENT CLUSTER PRINTED CIURCUIT LEFT GLOW PLUGS LINK FUSIBLE LOW BLOWER RELAY MED BLOWER RELAY MODE DOOR MOTOR ORG/ WIRE PANEL DIMMER SWITCH ASSEMBLY (INTERIOR LIGHTS SYSTEM) PNK WIRE PNK/BLK WIRE PNK/WHT WIRE PNL LPS FUSE POWERTRAIN CONTROL MODULE RIGHT GLOW PLUGS RR HVAC FUSE TEMP DOOR MOTOR TRANS FUSE TRANSFER CASE SWITCH VEHICLE SPEED SENSOR BUFFER MODULE W/ AIR CONDITIONING

A/C CLUTCH RELAY A/C CONTROL MODULE ANTILOCK BRAKE MODULE AUXILLIARY AUXILLIARY HEATER-A/C HEATER-A/C REAR LOGIC CONTROL MODULE AUXILLIARY BATTERY RELAY AUXILLIARY HEATER-A/C FRONT CONTROL BRAKE FUSE BRN WIRE BRN/WHT WIRE CONVENIENCE CENTER DK GRN WIRE ELECTRONIC TRANSMISSION 4-SPEED AUTOMATIC W/OVERDRIVE EXCEPT VIN Z FUSE FUSE BLOCK GRY WIRE HEATED OXYGEN SENSOR HEATER BLOWER SWITCH HEAVY DUTY ELECTRONIC TRANSMISSION 4-SPEED AUTOMATIC W/OVERDRIVE HIGH BLOWER RELAY HTR A/C FUSE IGNITION SWITCH INJ FUSE LOW BLOWER RELAY MED BLOWER RELAY MODE DOOR MOTOR ORG/ WIRE PANEL DIMMER SWITCH ASSEMBLY (INTERIOR LIGHTS SYSTEM) PNK WIRE PNK/BLK (OR PNK) WIRE PNK/BLK WIRE PNK/WHT WIRE PNL LPS FUSE RED WIRE RR HVAC FUSE TEMP DOOR MOTOR THROTTLE THROTTLE BODY FUEL BODY FUEL INJECTOR A INJECTOR B TRANS FUSE TRANSFER CASE SWITCH VEHICLE SPEED SENSOR BUFFER MODULE VIN Z ONLY W/ AIR CONDITIONING WHT WIRE