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

7.4L BACK-UP LAMPS CIRCUIT BLK WIRE BLK/WHT WIRE BLU WIRE BRN WIRE CRUISE CONTROL SYSTEM DK BLU WIRE DK GRN WIRE ENGINE CONTROLS SYSTEM GRN WIRE HAZARD HAZARD LAMPS FLASHER (INNER LEFT SIDE OF STEERING COLUMN SUPPORT BRACKET) HEAD OFF HEADLAMPS SWITCH HOT AT ALL TIMES HOT IN I/P FUSE BLOCK INSTRUMENT CLUSTER RIGHT TURN INDIC INTERIOR LAMPS SYSTEM LEFT FRONT PARK/ TURN SIGNAL LAMP LEFT FRONT SIDE MARKER LAMP LEFT REAR SIDE MARKER LAMP LEFT TAIL/ STOP/ TURN SIGNAL LAMP LEFT TURN INDIC LT BLU WIRE NCA WIRE NORMAL ORG/ WIRE PARK PARK TURN PPL PROVISION FOR CENTER HIGH MOUNTED STOP LAMP PROVISIONS FOR MARKER LAMPS RIGHT FRONT PARK/ TURN SIGNAL LAMP RIGHT FRONT SIDE MARKER LAMP RIGHT REAR SIDE MARKER LAMP RIGHT LICENSE LAMP LEFT LICENSE LAMP RIGHT TAIL/ STOP/ TURN SIGNAL LAMP RUN WIRE STOP-HAZ FUSE 11 TAIL LPS FUSE 7 TORQUE CONVERTER CLUTCH, STOP LAMPS SWITCH (BRAKE PEDAL SUPPORT BRACKET) TURN TURN B/U FUSE 5 TURN LEFT TURN RIGHT TURN SIGNAL FLASHER TURN SIGNAL SWITCH WHT WIRE YEL WIRE

7.4L BACKUP LAMPS CIRCUIT BLK WIRE BLK/WHT WIRE BLU WIRE BRN WIRE COOLING FAN NOTOR HARN BREAKOUT) CRUISE CONTROL SYSTEM DK BLU WIRE DK GRN WIRE ENGINE CONTROLS SYSTEM GRN WIRE HAZARD HAZARD LAMPS FLASHER (INNER LEFT SIDE OF MAIN SUPPORT BRACKET) HEAD OFF HEADLAMP BREAKOUT) HEADLAMP SWITCH CONNECTOR) HEADLAMPS SWITCH HOT AT ALL TIMES HOT IN I/P FUSE BLOCK INSTRUMENT CLUSTER RIGHT TURN INDIC INTERIOR LAMPS SYSTEM LEFT FRONT PARK, TURN SIGNAL (T/S) LAMP LEFT FRONT SIDE MARKER LAMP LEFT HEAD- LAMP BREAKOUT) LEFT HEADLAMP BREAKOUT) LEFT REAR SIDE MARKER LAMP LEFT TURN INDIC LT BLU WIRE NCA WIRE NORMAL ORG/ WIRE PARK PARK TURN PPL PROVISION FOR CENTER HIGH MOUNTED STOP LAMP PROVISIONS FOR LEFT TAIL, STOP, TURN SIGNAL (T/S) LAMPS PROVISIONS FOR MARKER LAMPS PROVISIONS FOR RIGHT TAIL, STOP, TURN SIGNAL (T/S) LAMPS RIGHT FRONT PARK, TURN SIGNAL (T/S) LAMP RIGHT FRONT SIDE MARKER LAMP RIGHT REAR SIDE MARKER LAMP RIGHT REAR LICENSE LAMP LEFT REAR LICENSE LAMP RUN WIRE STOP-HAZ FUSE 11 TAIL LAMPS FUSE 7 TORQUE CONVERTER CLUTCH, STOP LAMPS SWITCH (BRAKE PEDAL SUPPORT BRACKET) TURN TURN B/U FUSE 5 TURN LEFT TURN RIGHT TURN SIGNAL FLASHER TURN SIGNAL SWITCH WHT WIRE WINDSHIELD WIPER MOTOR BREAKOUT) YEL 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 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

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

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

1226 1225 TR SWITCH C TR SWITCH B TR SWITCH A 2-3 SHIFT SOLENOID VALVE 27 28 29 30 31 PPL 379 (OR 420) A/C SYSTEM A/T A/T M/T ANTILOCK BRAKES SYSTEM AUTOMATIC TRANSMISSION BATTERY BLK WIRE BLK/WHT WIRE BLU WIRE BLU/WHT WIRE BRN (OR LT BLU) WIRE BRN WIRE BRN/WHT (OR PPL) WIRE BRN/WHT WIRE CLOSURE SIGNAL BOOST SENSOR SIG PRESS CTRL SOL VLV LO CLUTCH PEDAL POSITION SWITCH (TOP OF CLUTCH PEDAL SUPORT) DK BLU WIRE DK BLU/WHT WIRE DK GRN WIRE DK GRN/WHT WIRE DK PNK/ PNK WIRE ECT SIGNAL GRN WIRE GRY WIRE LT BLU WIRE LT BLU/WHT WIRE LT GRN WIRE LT GRN/WHT WIRE ORG/ WIRE ORG/BLK WIRE PNK PNK PPL 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 WIRE PNK WIRE PNK/BLK WIRE POWERTRAIN CONTROL MODULE (PCM) (LEFT SIDE OF DRIVER'S ISLAND ON RELAY BRACKET) PPL PPL APP 2 GROUND APP 1 GROUND APP 1 SIG PPL CKP SEN GRD A/C REQUEST SIG PPL PPL PPL/WHT WIRE PRESSURE CONTROL SOLENOID VALVE RANGE MODE SELECTOR RED WIRE RED/BLK WIRE SENSOR GND SOLENOID VALVE 1-2 SHIFT SOLID STATE TAN WIRE TAN/BLK WIRE TCC PWM SOLENOID VALVE TCC/ABS BRAKE SW STOPLAMP SWITCH TIMING STEPPER MTR (HIGH) TIMING STEPPER MTR (LOW) TIMING STEPPER MTR (LOW) TRANSMISSION OUTPUT SPEED SENSOR (LEFT SIDE OF TRANS- MISSION, NEAR THE MIDDLE) TRANSMISSION SPEED INPUT TRANSMISSION TEMPERATURE SENSOR WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

27 28 29 30 31 PPL 5 VOLT REF ACCELERATOR PEDAL POSITION MODULE (ATTACHED TO ACCELERATOR PEDAL) APP 1 SENSOR APP 2 SENSOR APP 3 SENSOR BLK WIRE BLU WIRE BRN (OR LT BLU) WIRE BRN WIRE BRN/WHT WIRE CLOSURE GRD CLOSURE SIGNAL DK BLU/WHT WIRE DK GRN WIRE DK GRN/WHT WIRE ECM 1 FUSE 12 ELECTRONIC BRAKE CONTROL MODULE (BELOW RADIATOR, ON LOWER CROSSMEMBER) ENG 1 FUSE 15 ENGINE SHUT-OFF SOLENOID (AT FUEL INJECTION PUMP) FUEL SOL CTRL FUEL SOL HIGH FUEL SOL LOW FUEL SOLE- NOID FUEL SOLENOID DRIVER (ON SIDE OF FUEL INJECTION PUMP) GRN WIRE GRY WIRE HIGH LOW HIGH RES SIG HOT AT ALL TIMES HOT IN HOT IN RUN OR START I-3 FUSE 9 I/P FUSE BLOCK IGNITION IGNITION TIMING STEPPER MOTOR (PART OF FUEL INJECTION PUMP) LOW HIGH LT BLU WIRE LT GRN WIRE LT PPL OPTICAL FUEL TEMPERATURE SENSOR (PART OF FUEL INJECTION PUMP ASSEMBLY) ORG/ WIRE ORG/BLK WIRE PNK PNK PPL 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 WIRE PNK WIRE PNK/BLK WIRE PPL PPL (ENG HARN, APPROX 32 CM FROM BREAKOUT FOR BATTERY JUNCTION BLOCK) PUMP CAM SIG RED WIRE RED/BLK WIRE RUN WIRE SENSOR GROUND STOP/HAZ FUSE 11 TAN WIRE TAN/BLK WIRE TORQUE CONVERTER CLUTCH (TCC), STOPLAMPS SWITCH (AT BRAKE PEDAL SUPPORT) TRANS FUSE 17 WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

A/T A/T M/T BLK WIRE BLK/WHT WIRE BLU WIRE BRN (OR LT BLU) WIRE BRN WIRE BRN/WHT WIRE DK BLU WIRE DK BLU/WHT WIRE DK GRN WIRE DK GRN/WHT WIRE ECM-BAT FUSE 6 ENG BAT FUSE 10 FUEL HEATER (PART OF FUEL/WATER SEPARATOR) FUEL LIFT PUMP (INSIDE RIGHT FRAME RAIL) FUEL PUMP PRIME CONNECTOR (TAPED TO FUEL PUMP RELAY BREAKOUT) FUEL PUMP RELAY (ON ENGINE FIREWALL RELAY BRACKET, UNDER BATTERY JUNCTION BLOCK) GAUGES FUSE 8 GRN WIRE GRY WIRE HOT AT ALL TIMES HOT IN RUN AND START I/P FUSE BLOCK INDICATOR INSTRUMENT CLUSTER LT BLU WIRE LT GRN WIRE M/T MALFUNCTION INDICATOR LAMP (MIL) ORG/ WIRE PNK FEDERAL WIRE PNK PNK WIRE PNK WIRE RED WIRE SERVICE THROTTLE SOON INDICATOR SPEED METER TAN WIRE WAIT TO WASTEGATE SOLENOID (TOP LEFT REAR OF ENG) WATER IN FUEL INDICATOR WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

A/T A/T M/T BATTERY FEED BATTERY JUNCTION BLOCK (ON LEFT REAR OF ENG COMPT) BLK WIRE BLU WIRE BRN WIRE CRANK FUSE (UPPER RIGHT SIDE OF STEERING COLUMN SUPPORT) DK BLU WIRE ENG 1 FUSE 15 FUEL HEATER (REAR OF INTAKE MANIFOLD, PART OF FUEL/ WATER SEPARATOR) FUEL INJECTION PUMP COLD ADVANCE SOLENOID (AT FUEL INJECTION PUMP) FUSIBLE LINK FUSIBLE LINK (12 GA- FUSIBLE LINK (16 GA- FUSIBLE LINK (22 GA-RUST) FUSIBLE LINKS GLOW PLUG CONTROLLER (LEFT REAR OF ENG, NEAR FIREWALL) GLOW PLUG CTRL GLOW PLUG OUT GROUND HOT AT ALL TIMES HOT IN RUN OR START I/P FUSE BLOCK (BEHIND DASH PANEL) (BODY BUILDER INSTALLED) IDLE SPEED CONTROL ACTUATOR SOLENOID (ON BRACKET ON FRONT FUEL INJECTION PUMP) IGN FEED IND LAMP OUT GROUND IGNITION SWITCH LEFT BANK GLOW PLUGS LOCK OFF LT GRN/BLK WIRE NOT USED STARTER FEED ORG/ WIRE PNK IGN FEED WIRE PNK WIRE PPL PPL PPL PPL S STUD RED WIRE RIGHT BANK GLOW PLUGS RUN WIRE STARTER RELAY (ON ENG FIREWALL RELAY BRACKET, UNDER BATTERY JUNCTION BLOCK) STARTER SOLENOID (ON STARTER, AT LOWER RIGHT SIDE OF ENGINE) STUD WATER IN FUEL INDICATOR SENSOR WHT WIRE YEL WIRE YEL/BLK WIRE