GMC Forward Control P3500 (1985-1999) red Wiring diagrams

1-2 SHIFT SOL 1-2 SHIFT SOLENOID 2-3 SHIFT SOL 2-3 SHIFT SOLENOID A/T ISS HI IN A/T ISS LO IN AUTO TRANSMISSION INPUT SHAFT SPEED SENSOR (INSIDE FRONT OF TRANSMISSION) AUTOMATIC TRANSMISSION BATTERY IN BLK WIRE BLK/WHT WIRE BRAKE SWITCH INPUT BRN WIRE BRN/WHT WIRE DATA CLASS II DK BLU WIRE DK BLU/WHT WIRE ECM BATT FUSE ECM I FUSE ECT SENS INPUT ENG 1 FUSE ENGINE COOLANT TEMP SENSOR (TOP FRONT OF ENGINE) FUSE GAUGES FUSE GRY WIRE HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START I/P FUSE BLOCK IGNITION IN INSTRUMENT CLUSTER LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE MALFUNCTION INDICATOR LAMP MIL CONTROL ORG/ WIRE PCM GROUND PCS SOL HI OUT PCS SOL LO OUT PNK WIRE PPL PPL DATA LINK CONNECTOR PPL/WHT WIRE PRESS CTRL SOLENOID RANGE SIGNAL "A" RANGE SIGNAL "B" RANGE SIGNAL "C" RED WIRE RED/BLK WIRE SENSOR GROUND SENSOR RETURN TCC PWM SOL TCC PWM SOLENOID TCC/STOP- LAMP SWITCH (ON BRAKE PEDAL BRACKET) THROTTLE POSITION SENSOR (MOUNTED TO SIDE OF THROTTLE BODY) TP SENS INPUT TRANS FLUID TEMP SENSOR TRANS FUSE TRANS RANGE PRESSURE SWITCH ASSEMBLY TRANS TEMP SIG IN VEHICLE CONTROL MODULE (VCM) (BEHIND LEFT HEADLIGHT) VEHICLE SPEED SENSOR (LEFT REAR OF TRANSMISSION) VSS HI VSS LO YEL WIRE YEL/BLK WIRE

1-3 FUSE 9 12 2 DATA LINK CONNECTOR (BELOW DASH, NEAR STEERING COLUMN) PPL ABS IND. BATTERY GROUND BLK (OR BLK/WHT) WIRE BLK WIRE BRAKE IND BRAKE PRESSURE DIFFERENTIAL SWITCH (INTERNAL TO ELECTRONIC BRAKE CONTROL MODULE) BRN WIRE DIESEL DIESEL: ENGINE HARN, 32 CM FROM BREAKOUT TO BATTERY JUNCTION BLOCK) DIODE NETWORK (ON I/P HARNESS, BODY BUILDER INSTALLED) DK GRN WIRE ELECTRONIC BRAKE CONTROL MODULE (BELOW RADIATOR, ON LOWER CROSSMEMBER) FUSE LINK (IN BATTERY JUNCTION BLOCK, AT LEFT REAR OF ENGINE COMPT) GAS GAS DIESEL GAUGES FUSE 8 HOT AT ALL TIMES HOT IN RUN HOT IN RUN AND START I/P FUSE BLOCK (BEHIND DASH PANEL) (BODY BUILDER INSTALLED) IGNITION ABS LAMP CONTROL BRAKE SW INPUT INSTRUMENT CLUSTER LEFT FRONT WHEEL SPEED SENSOR LT BLU WIRE LT GRN WIRE NCA WIRE PNK WIRE PPL PPL PPL 1807 680 RED WIRE RIGHT FRONT WHEEL SPEED SENSOR SENSOR LOW SENSOR LOW SENSOR HIGH SENSOR HIGH 873 833 STOPLAMPS SWITCH (AT BRAKE PEDAL SUPPORT) TAN WIRE TAN/WHT WIRE VEHICLE SPEED SENSOR CALIBRATOR (LEFT SIDE OF DRIVER'S ISLAND ON RELAY BRACKET) WARNINGS SYSTEM YEL WIRE YEL/BLK WIRE

ABS IND. BLK WIRE BLK/ WHT WIRE BRAKE IND BRAKE PRESSURE DIFFERENTIAL SWITCH BRAKE/ BRN WIRE DIESEL GASOLINE DK GRN WIRE ELECTRONIC BRAKE CONTROL MODULE (BELOW RADIATOR OF FIRST CROSSMEMBER) FUSIBLE LINK HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START GAUGES FUSE I-3 FUSE I/P FUSE BLOCK IGN ABS LAMP CONTROL BRAKE SW INPUT INSTRUMENT CLUSTER LEFT FRONT WHEEL SPEED SENSOR LFT FRT SENSOR (-) LT BLU WIRE LT GRN WIRE PNK WIRE PPL PPL PPL PUMP MOTOR POWER PUMP MOTOR GROUND RED WIRE RIGHT FRONT WHEEL SPEED SENSOR RT FRT SENSOR (-) LFT FRT SENSOR (+) RT FRT SENSOR (+) TAN WIRE TAN/WHT WIRE TCC/ STOPLAMP SWITCH UNDERHOOD FUSE-RELAY CENTER VEHICLE CONTROL MODULE (LEFT SIDE OF ENGINE COMPT) VEHICLE SPEED SIG VSS BUFFER (LEFT SIDE OF INTERIOR BULKHEAD) VSS SIG SERIAL DATA LINE SERIAL DATA SIGNAL BRAKE LAMP CONTROL EBCM GROUND WHT WIRE YEL WIRE YEL/BLK WIRE

BLK WIRE BLU WIRE BREAKOUT FOR HEADLAMP SWITCH) BULB TEST DAYTIME RUNNING LAMPS MODULE (ATTACHED TO I/P HARNESS AT STEERING COLUMN) DAYTIME RUNNING LAMPS RELAY (ON MAIN SUPPORT BRACKET AT DRIVER'S ISLAND) DAYTIME RUNNING LAMPS RELAY 2 DIODE NETWORK DK BLU WIRE DK GRN/WHT WIRE DRL INDICATOR FOR LEFT HEADLAMP) FUSIBLE LINK (16 GA- GAUGES FUSE GRN WIRE HEAD- LAMP DIMMER SWITCH HEADLAMPS SWITCH HI BEAM INDICATOR HI LO HOT AT ALL TIMES HOT IN RUN OR START I/P FUSE BLOCK IGNITION SWITCH INSTRUMENT CLUSTER INSTRUMENT CLUSTER SYSTEM LEFT HEAD- LAMP LEFT HIGH BEAM HEAD- LAMP LO HI LOCK OFF LT BLU WIRE LT GRN WIRE LT GRN/BLK WIRE ORG/ WIRE PARK BRAKE IN FOG LAMPS PARK BRAKE INDICATOR SWITCH (ON PARK BRAKE) PARK HEAD OFF PNK IGNITION LAMP FEED HI BM FEED HI BM INDICATOR RELAY OUT GROUND WIRE PNK WIRE RED WIRE RIGHT HEAD- LAMP RIGHT HIGH BEAM HEAD- LAMP RUN WIRE TAN WIRE WHT WIRE YEL WIRE

BLK WIRE BLK/WHT WIRE FOR LEFT HEADLAMP) GRN WIRE HEAD PARK HEADLAMPS SWITCH HOT AT ALL TIMES INSTRUMENT CLUSTER HI BEAM INDICATOR LEFT HEAD- LAMP HI HI LO LEFT HIGH BEAM HEAD- LAMP LO HEADLAMPS DIMMER SWITCH LT GRN WIRE LT LT OFF RED WIRE RIGHT HEAD LAMP LO RIGHT HIGH BEAM HEAD- LAMP TAN WIRE YEL WIRE

BLK WIRE BLU WIRE BREAKOUT FOR HEADLAMP SW) BULB TEST DAYTIME RUNNING LAMPS MODULE (ATTACHED TO I/P HARNESS AT STEERING COLUMN) DAYTIME RUNNING LAMPS RELAY (ON MAIN SUPPORT BRACKET AT DRIVER'S ISLAND) DIODE NETWORK DK BLU WIRE DK GRN/WHT WIRE DRL INDICATOR FUSIBLE LINK (16 GA- GAUGES FUSE GRN WIRE HEAD- LAMP DIMMER SWITCH HEADLAMPS SWITCH HI BEAM INDICATOR HOT AT ALL TIMES HOT IN RUN OR START I/P FUSE BLOCK IGNITION SWITCH INSTRUMENT CLUSTER INSTRUMENT CLUSTER SYSTEM LEFT HEAD- LAMP LO HI HI LO LOCK OFF LT BLU WIRE LT GRN WIRE LT GRN/BLK WIRE LT LT ORG/ WIRE PARK BRAKE IN FOG LAMPS PARK BRAKE INDICATOR SWITCH (ON PARK BRAKE) PARK HEAD OFF PNK IGNITION LAMP FEED HI BM FEED HI BM INDICATOR RELAY OUT GROUND WIRE PNK WIRE RED WIRE RIGHT HEAD- LAMP RUN WIRE TAN WIRE WHT WIRE YEL WIRE

BLK WIRE BLK/WHT WIRE FUSIBLE LINK (16 GA- GRN WIRE HEAD HEADLAMPS SWITCH HI BEAM INDICATOR HOT AT ALL TIMES INSTRUMENT CLUSTER LEFT HEADLAMP HI LO HEADLAMPS DIMMER SWITCH LT GRN WIRE OFF PARK RED WIRE RIGHT HEADLAMP HI LO TAN WIRE YEL WIRE

A/C COMPRESSOR RELAY ACCESSORY JUNCTION BLOCK (LEFT INTERIOR BULKHEAD, NEAR RELAY BRACKET) AUXILIARY ENGINE COOLANT FAN RELAY (DIESEL ONLY) GLOW PLUG CONTROLLER (DIESEL) BATT BUS BATTERY BATTERY JUNCTION BLOCK (LEFT SIDE OF ENGINE BULKHEAD) BLK WIRE BLU WIRE DATA LINK CONNECTOR DIESEL DOME LAMP (PROVISIONS FOR) ECM-BAT FUSE 6 ELECTRONIC BRAKE CONTROL MODULE ENG BAT FUSE 10 FUEL PUMP RELAY VEHICLE CONTROL MODULE FUSIBLE LINK (10 GA-RUST) FUSIBLE LINK (12 GA- FUSIBLE LINK (14 GA- FUSIBLE LINK (16 GA- FUSIBLE LINK (18 GA- GAS GENERATOR GRY WIRE HAZARD LAMP FLASHER HEADLAMPS SWITCH HORN DM FUSE 3 HORN RELAY I/P FUSE BLOCK (DASH PANEL PROVIDED BY BODY BUILDER) ORG/ WIRE OTHERS POWERTRAIN CONTROL MODULE PWR BUS PWR CIRCUIT BREAKER RED WIRE REMOTE BATTERY ACCESS TERMINAL BLOCK (REAR OF RIGHT RADIATOR CORE SUPPORT PANEL) SEAT BELT ALARM MODULE SECONDARY BATTERY (DIESEL ONLY) STARTER RELAY STARTER SOLENOID STOP-HAZ FUSE 11 STUD TAIL LPS FUSE 7 TO IGNITION SWITCH (DIAGRAM 2 OF 4) TORQUE CONVERTER CLUTCH, STOPLAMPS SWITCH TRANSMISSION CONTROL MODULE (A/T ONLY) FUEL PUMP RELAY W/DELUXE SCHOOL BUS OPTION

4.3L A/T ACC BUS AUTOMATIC TRANSMISSION AUXILIARY ENGINE COOLANT FAN RELAY BRN WIRE CAMSHAFT POSITION SENSOR (5.7L) CLUTCH PEDAL POSITION SWITCH COLD ADVANCE SOLENOID AND ENGINE COOLANT TEMPERATURE SWITCH FUEL HEATER CRANK FUSE 18 CRK (START) LOCK ON (RUN) OFF CRK (START) ON (RUN) LOCK OFF CRK (START) ON (RUN) OFF DIESEL DK BLU WIRE ENG 1 FUSE 15 ENGINE SHUT-OFF SOLENOID FUEL SOLENOID DRIVER EVAP CANISTER VENT VALVE (4.3L) EVAPORATIVE EMISSIONS CANISTER PURGE VALVE FROM FUSIBLE LINK GAS GLOW PLUG CONTROLLER HEATED OXYGEN SENSOR BANK 1 SENSOR 1 CAMSHAFT POSITION SENSOR (4.3L) HEATED OXYGEN SENSOR BANK 2 SENSOR 1 HEATED OXYGEN SENSOR BANK 1 SENSOR 2 HEATED OXYGEN SENSOR BANK 2 SENSOR 2 IGNITION SWITCH IN-LINE FUSE BLOCK (NEAR RIGHT SIDE OF STEERING COLUMN) LOCK M/T MASS AIR FLOW SENSOR (4.3L/ 5.7L) ORG/ WIRE PARK/NEUTRAL POSITION AND BACKUP LAMPS SWITCH PNK PNK WIRE PNK WIRE PROVISIONS FOR WINDSHIELD WASHER MOTOR RADIO FUSE 4 RED WIRE TO I/P FUSE BLOCK (DIAGRAM 4 OF 4) TRANS FUSE 17 WATER IN FUEL INDICATOR SENSOR WHT WIRE WINDSHIELD WIPER/ WASHER SWITCH WIPER FUSE 14 YEL WIRE

7.4L 7.4L VIN J 6.5L VIN F A/C COMPRESSOR RELAY FAN CONTROL RELAY ALTERNATOR BATTERY BATTERY JUNCTION BLOCK (ON FORWARD LEFT SIDE OF THE BULKHEAD) BLK WIRE BLU WIRE BUSS BAR CONNECTOR FOR DOME LAMP DATA LINK CONNECTOR DIESEL ECM-BAT FUSE 6 ELECTRONIC BRAKE CONTROL MODULE ENG BAT FUSE 10 FAN CONTROL RELAY GLOW PLUG CONTROLLER FUEL PUMP RELAY FUSIBLE LINK FUSIBLE LINK (10 GA- FUSIBLE LINK (10 GA-RUST) FUSIBLE LINK (14 GA- FUSIBLE LINK (16 GA- FUSIBLE LINK (18 GA. FUSIBLE LINK (12 GA. GRY WIRE HAZARD FLASHER HEADLAMPS SWITCH HEADLAMPS SWITCH STOPLAMP SWITCH HORN DM FUSE 3 HORN RELAY I/P FUSE BLOCK (MOUNTED ON THE DASH) IGNITION SWITCH (DIAGRAM 2 OF 4) ORG/ WIRE PARK BRAKE PUMP MOTOR RELAY POWERTRAIN CONTROL MODULE VEHICLE CONTROL MODULE PWR CIRCUIT BREAKER 2 RED WIRE SEATBELT AND LAMPS ALARM MODULE SECONDARY BATTERY (DIESEL ONLY) STARTER MOTOR STARTER RELAY STOP-HAZ FUSE 11 TAIL LAMPS FUSE 7