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

1-2 SHIFT SOL 1-2 SHIFT SOLENOID 2-3 SHIFT SOL 2-3 SHIFT SOLENOID A/C COMPRESSOR RELAY, GENERATOR, SEAT BELT/ HEADLAMPS ALARM MODULE A/T INPUT SPEED SENSOR (LEFT SIDE OF TRANSMISSION) A/T ISS HI IN A/T ISS LO IN A/T OUTPUT SPEED SENSOR ANTI-LOCK BRAKES, CRUISE CONTROL, SHIFT INTERLOCK SYSTEMS AUTOMATIC TRANSMISSION BATTERY IN BLK WIRE BLK/WHT WIRE BRAKE SWITCH INPUT BRN WIRE BRN/WHT WIRE BUSS BAR GAUGES FUSE 8 DATA CLASS II DK BLU WIRE DK BLU/WHT WIRE ECM 1 FUSE 12 ECM-BAT FUSE 6 ECT SENS INPUT ELECTRONIC BRAKE CONTROL MODULE, CRUISE CONTROL MODULE ENGINE CONTROLS SYSTEM FUEL INJECTORS (ENGINE CONTROLS SYSTEM) FUEL PUMP RELAY, SWITCH GRY WIRE HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START I-3 FUSE 9 I/P FUSE BLOCK IGNITION IN INSTRUMENT CLUSTER LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE MIL CONTROL ORG/ WIRE PCM GROUND PCS SOL HI OUT PCS SOL LO OUT PNK WIRE PPL PPL DATA LINK CONNECTOR (PARTIAL) (BELOW DASH NEAR STEERING COLUMN) PPL/WHT WIRE PRESS CTRL SOLENOID RANGE SIGNAL "A" RANGE SIGNAL "B" RANGE SIGNAL "C" RED WIRE RED/BLK WIRE SENSOR GROUND SENSOR RETURN SERVICE ENGINE SOON INDICATOR TCC PWM SOL TCC PWM SOLENOID TCC/ STOP LAMPS SWITCH TP SENS INPUT TRANS FLUID TEMP SENSOR TRANS FUSE 17 TRANS RANGE PRESSURE SWITCH ASSEMBLY TRANS TEMP SIG IN TWISTED WIRE PAIR VEHICLE CONTROL MODULE (CENTER FRONT OF ENGINE COMPT) VEHICLE SPEED SENSOR (LEFT REAR OF TRANSMISSION) VSS HI VSS LO YEL WIRE YEL/BLK WIRE

1-2 SHIFT SOL 1-2 SHIFT SOLENOID 2-3 SHIFT SOL 2-3 SHIFT SOLENOID A/C COMPRESSOR RELAY, GENERATOR, SEAT BELT/ HEADLAMPS ALARM MODULE A/T INPUT SPEED SENSOR (LEFT SIDE OF TRANSMISSION) A/T ISS HI IN A/T ISS LO IN A/T OUTPUT SPEED SENSOR ANTI-LOCK BRAKES, CRUISE CONTROL, SHIFT INTERLOCK SYSTEMS AUTOMATIC TRANSMISSION BATTERY IN BLK WIRE BLK/WHT WIRE BRAKE SWITCH INPUT BRN WIRE BRN/WHT WIRE BUSS BAR GAUGES FUSE 8 DATA CLASS II DK BLU WIRE DK BLU/WHT WIRE ECM 1 FUSE 12 ECM-BAT FUSE 6 ECT SENS INPUT ELECTRONIC BRAKE CONTROL MODULE, CRUISE CONTROL MODULE ENGINE CONTROLS SYSTEM FUEL INJECTORS (ENGINE CONTROLS SYSTEM) FUEL PUMP RELAY, SWITCH GRY WIRE HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START I-3 FUSE 9 I/P FUSE BLOCK IGNITION IN INSTRUMENT CLUSTER LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE MIL CONTROL ORG/ WIRE PCM GROUND PCS SOL HI OUT PCS SOL LO OUT PNK WIRE PPL PPL DATA LINK CONNECTOR (PARTIAL) (BELOW DASH NEAR STEERING COLUMN) PPL/WHT WIRE PRESS CTRL SOLENOID RANGE SIGNAL "A" RANGE SIGNAL "B" RANGE SIGNAL "C" RED WIRE RED/BLK WIRE SENSOR GROUND SENSOR RETURN SERVICE ENGINE SOON INDICATOR TCC PWM SOL TCC PWM SOLENOID TCC/ STOP LAMPS SWITCH TP SENS INPUT TRANS FLUID TEMP SENSOR TRANS FUSE 17 TRANS RANGE PRESSURE SWITCH ASSEMBLY TRANS TEMP SIG IN TWISTED WIRE PAIR VEHICLE CONTROL MODULE (CENTER FRONT OF ENGINE COMPT) VEHICLE SPEED SENSOR (LEFT REAR OF TRANSMISSION) VSS HI VSS LO YEL WIRE YEL/BLK WIRE

1-2 SHIFT SOL 1-2 SHIFT SOLENOID 2-3 SHIFT SOL 2-3 SHIFT SOLENOID A/C COMPRESSOR RELAY, GENERATOR, SEAT BELT/ HEADLAMPS ALARM MODULE A/T INPUT SPEED SENSOR (LEFT SIDE OF TRANSMISSION) A/T ISS HI IN A/T ISS LO IN A/T OUTPUT SPEED SENSOR ANTI-LOCK BRAKES, CRUISE CONTROL, SHIFT INTERLOCK SYSTEMS AUTOMATIC TRANSMISSION BATTERY IN BLK WIRE BLK/WHT WIRE BRAKE SWITCH INPUT BRN WIRE BRN/WHT WIRE BUSS BAR GAUGES FUSE 8 DATA CLASS II DK BLU WIRE DK BLU/WHT WIRE ECM 1 FUSE 12 ECM-BAT FUSE 6 ECT SENS INPUT ELECTRONIC BRAKE CONTROL MODULE, CRUISE CONTROL MODULE ENGINE CONTROLS SYSTEM FUEL INJECTORS (ENGINE CONTROLS SYSTEM) FUEL PUMP RELAY, SWITCH GRY WIRE HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START I-3 FUSE 9 I/P FUSE BLOCK IGNITION IN INSTRUMENT CLUSTER LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE MIL CONTROL ORG/ WIRE PCM GROUND PCS SOL HI OUT PCS SOL LO OUT PNK WIRE PPL PPL DATA LINK CONNECTOR (PARTIAL) (BELOW DASH NEAR STEERING COLUMN) PPL/WHT WIRE PRESS CTRL SOLENOID RANGE SIGNAL "A" RANGE SIGNAL "B" RANGE SIGNAL "C" RED WIRE RED/BLK WIRE SENSOR GROUND SENSOR RETURN SERVICE ENGINE SOON INDICATOR TCC PWM SOL TCC PWM SOLENOID TCC/ STOP LAMPS SWITCH TP SENS INPUT TRANS FLUID TEMP SENSOR TRANS FUSE 17 TRANS RANGE PRESSURE SWITCH ASSEMBLY TRANS TEMP SIG IN TWISTED WIRE PAIR VEHICLE CONTROL MODULE (CENTER FRONT OF ENGINE COMPT) VEHICLE SPEED SENSOR (LEFT REAR OF TRANSMISSION) VSS HI VSS LO YEL WIRE YEL/BLK 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

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

6.5L VIN F AUTO APPLY FUSE 19 AUTOMATIC TRANSMISSION BRN WIRE CRANK FUSE 18 DAYTIME RUNNING LAMP CONTROL MODULE DIESEL DIODE NETWORK DK BLU WIRE ENG-1 FUSE TRANS FUSE 17 ENGINE SHUT OFF SOLENOID EVAPORATIVE EMISSIONS CANISTER PURGE VALVE SOLENOID FROM FUSE PANEL) FROM FUSIBLE LINK (DIAGRAM 1 OF 4) FROM I/P FUSE BLOCK) PNK WIRE FUEL SOLENOID DRIVER HARN BREAKOUT) PNK WIRE HEATED OXYGEN SENSOR BANK 1 SENSOR 2 HEATED OXYGEN SENSOR BANK 2 SENSOR 1 CAMSHAFT POSITION SENSOR FAN CONTROL RELAY HEATED OXYGEN SENSOR BANK 2 SENSOR 2 I/P FUSE BLOCK (MOUNTED ON THE DASH) IGNITION SWITCH INSTRUMENT CLUSTER BREAKOUT) INSTRUMENT CLUSTER ENGINE COOLANT LEVEL SWITCH LOCK OFF LT BLU WIRE MASS AIR FLOW SENSOR HEATED OXYGEN SENSOR BANK 1 SENSOR 1 NCA WIRE ORG/ WIRE PARK BRAKE ALARM PARK BRAKE ALARM RELAY PARK BRAKE LOW PRESSURE INDICATOR SWITCH PARK BRAKE PULL BUTTON SWITCH PARK BRAKE PULL BUTTON RELAY PARK BRAKE SWITCH PARK/ NEUTRAL POSITION AND BACKUP LAMPS SWITCH PARK/NEUTRAL POSITION AND BACKUP LAMPS SWITCH PASSTHROUGH 6.5L: ENG HARN, PNK DIMMER SWITCH WIRE PNK PNK WIRE PNK WIRE RADIO FUSE 4 RED WIRE RELAY SOCKETS) RUN WIRE TO AUX FUSE (DIAGRAM 4 OF 4) TO GAUGES FUSE (DIAGRAM 4 OF 4) WHT WIRE WINDSHIELD WIPER MOTOR WIPER FUSE 14 YEL WIRE YEL/BLK WIRE

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