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

2-3 SHIFT SOL 6 9 DATA LINK CONNECTOR BLK WIRE BRN WIRE BRN/WHT WIRE DK BLU WIRE DK BLU/WHT WIRE ECM BAT FUSE ECM I FUSE ENGINE COOLANT TEMPERATURE (ECT) SENSOR (TOP FRONT OF ENGINE) GAUGES FUSE GRY WIRE GRY/RED WIRE HOT AT ALL TIMES HOT IN HOT IN RUN OR START HOT IN RUN, BULB TEST OR START I-3 FUSE I/P FUSE BLOCK INSTRUMENT CLUSTER LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE ORG/ WIRE PNK IGNITION FEED WIRE PNK WIRE POWERTRAIN CONTROL MODULE (PCM) (LEFT SIDE OF DRIVER'S ISLAND) PPL PPL PNK WIRE PPL/WHT WIRE PRESSURE CONTROL SOLENOID RANGE MODE SELECTOR RED WIRE RED/BLK WIRE RUN WIRE SERVICE ENGINE SOON INDIC SPEED SENSOR (LEFT REAR SIDE OF TRANSMISSION) TAN WIRE TCC PWM SOL 1-2 SHIFT SOL TCC/BRAKE SWITCH (ON BRAKE PEDAL BRACKET) THROTTLE POSITION SENSOR (ON SIDE OF THROTTLE BODY) TRANS FLUID TEMP (TFT) SENSOR TRANS FUSE TRANSMISSION TRANSMISSION INPUT SHAFT SPEED SENSOR (FRONT OF TRANSMISSION) VEHICLE SPEED SENSOR BUFFER WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

2-3 SHIFT SOL A/T INPUT SPEED SENSOR (LEFT SIDE OF TRANSMISSION) ANTI-LOCK BRAKES AUTOMATIC TRANSMISSION BLK WIRE BRN WIRE BRN/WHT WIRE BUSS BAR CRUISE CONTROL SYSTEMS DASH FUSE BLOCK DATA LINK CONNECTOR (PARTIAL) (BELOW DASH, NEAR STEERING COLUMN) DK BLU WIRE DK BLU/WHT WIRE ECM BAT FUSE ECM I FUSE ENGINE CONTROLS SYSTEMS ENGINE COOLANT TEMPERATURE SENSOR (TOP FRONT OF ENGINE) FUEL INJECTORS (ENGINE CONTROLS) FUEL PUMP RELAY GAUGES FUSE GRY WIRE GRY/RED WIRE HOT AT ALL TIMES HOT IN HOT IN RUN OR START HOT IN RUN, BULB TEST OR START I-3 FUSE INSTRUMENT CLUSTER LT BLU/WHT WIRE LT GRN WIRE LT GRN/BLK WIRE ORG/ WIRE PNK IGNITION FEED WIRE PNK WIRE POWERTRAIN CONTROL MODULE (LEFT SIDE OF DASH) PPL PPL PNK WIRE PPL/WHT WIRE PRESSURE CONTROL SOL RANGE MODE SELECTOR RED WIRE RED/BLK WIRE RUN WIRE SERVICE ENGINE SOON INDICATOR STOP LAMPS, TORQUE CONVERTER BRAKE SWITCH SWITCH TAN WIRE TCC PWM SOL 1-2 SHIFT SOL THROTTLE POSITION SENSOR (ON SIDE OF THROTTLE BODY) TRANS FLUID TEMP SENSOR TRANS FUSE VEHICLE SPEED SENSOR (LEFT REAR SIDE OF TRANSMISSION) VEHICLE SPEED SENSOR BUFFER (ABOVE ACCELERATOR PEDAL) WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

BLK WIRE DAYTIME RUNNING LAMPS CONTROL MODULE (ATTACHED TO I/P HARNESS) DAYTIME RUNNING LAMPS RELAY (LEFT SIDE OF DASH, ON RELAY BRACKET) DIODE NETWORK (ON I/P HARNESS) DK BLU WIRE DK GRN/WHT WIRE DRL INDICATOR FUSE BLOCK BREAKOUT) FUSIBLE LINK (16 GA- GAUGES FUSE 8 GRN WIRE HEADLAMP DIMMER SWITCH HEADLAMPS SWITCH OFF HI BEAM INDICATOR HI LO HOT AT ALL TIMES HOT IN RUN OR START I/P FUSE BLOCK IGNITION SWITCH INSTRUMENT CLUSTER LEFT HEAD- LAMP LO HI 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 LEVER) PARK HEAD PNK IGNITION LAMP FEED HI BM INPUT HI BM INDICATOR RELAY CONTROL GROUND WIRE PNK WIRE RED WIRE RIGHT HEAD- LAMP RUN WIRE TAN WIRE WHT WIRE YEL WIRE

ACC RADIO FUSE ACCY ACCY BULB TEST LOCK ACCY BULB TEST LOCK OFF AUTO APPLY PARK BRAKE AUX CB AUX CIRCUIT BREAKER HTR FUSE AUXILIARY COOLING FAN RELAY AUXILIARY COOLING FAN RELAY DAYTIME RUNNING LAMPS BATTERY BATTERY JUNCTION BLOCK BLK WIRE BLK/RED WIRE BRAKE WARNING ALARM BUZZER BRN WIRE BULB TEST DAYTIME RUNNING LAMPS RELAY DAYTIME RUNNING LAMPS MODULE DK GRN WIRE FROM PANEL DIMMER SWITCH ASSEMBLY (INTERIOR LIGHTS SYSTEM) FUEL PUMP RELAY FUEL PUMP OIL PRESSURE SWITCH HAZARD FLASHER FUSE BLOCK FUSIBLE FUSIBLE LINK GENERATOR GRY WIRE HEADLIGHT SWITCH HORN RELAY HORN/DM I/P CLUSTER BRAKE PRESSURE WARNING SWITCH IGNITION SWITCH INSTRUMENT CLUSTER LINK LOCK OFF LPS BUS GAGES FUSE INSTR-LPS FUSE OFF ORG/ WIRE PARK BRAKE WARNING SWITCH PCM PNK WIRE PNK/ WHT WIRE PNK/BLK WIRE PNK/WHT WIRE POWERTRAIN CONTROL MODULE PPL PWR ECM-BAT CIRCUIT BREAKER FUSE RED WIRE RELAY RUN WIRE SHUNT STARTER MOTOR STOP- HZ FUSE STOPLAMP SWITCH TAIL LPS FUSE FUSE TAN/WHT WIRE TO ALT, ECM-CRNK, TURN-B/U, TRANS, INJ FUSES AND IGNITION COIL TRANSMISSION POSITION INDICATOR LAMP WHT WIRE WINDSHIELD WIPER MOTOR WIPER SWITCH MODULE WIPER FUSE YEL WIRE

3 121 PNK WIRE 4.3L AND 7.4L 5.7L ACCY ALT FUSE BLK WIRE BLK/RED WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (CENTER REAR OF ENGINE) DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE ENGINE COOLANT TEMPERATURE SENSOR (TOP FRONT OF ENGINE) FUSE BLOCK GRY WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START IDLE SPEED ACTUATOR CONTROL SOLENOID (NO LOCATION AVAILABLE) IGNITION COIL (TOP RIGHT REAR OF ENGINE) IGNITION SWITCH INSTRUMENT CLUSTER KNOCK SENSOR (LEFT REAR OF ENGINE, NEAR OIL PRESSURE SENDER) KNOCK SENSOR MODULE (TOP RIGHT SIDE OF ENGINE) LOCK OFF LT BLU/WHT WIRE LT GRN WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR MANIFOLD ABSOLUTE PRESSURE SENSOR (ABOVE VALVE COVER) NCA WIRE ORG/ WIRE PNK 26 27 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 2 3 4 PPL 24 25 PPL/WHT WIRE PROVISIONS FOR TACHOMETER RED WIRE RED/BLK WIRE RUN WIRE TAN/BLK WIRE TCC/BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) THROTTLE POSITION SENSOR (ON THROTTLE BODY) TRANS FUSE WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

ACCY ALT FUSE BLK WIRE BLK/RED WIRE BLK/WHT WIRE BRN WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (TOP REAR OF ENGINE) DK BLU WIRE DK GRN/WHT WIRE EGR SOLENOID (TOP RIGHT SIDE OF ENGINE) ENGINE GROUND FUEL PUMP AND SENDER (IN FUEL TANK) FUEL PUMP OIL PRESSURE SWITCH (TOP REAR OF ENGINE) FUEL PUMP PRIME CONNECTOR FUEL PUMP RELAY (LOWER LEFT SIDE OF SHIPPING PANEL) FUSE BLOCK GRY WIRE HEATED OXYGEN SENSOR (IN EXHAUST MANIFOLD) HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START IGNITION COIL (TOP OF ENGINE NEAR DISTRIBUTOR) IGNITION SWITCH INSTRUMENT CLUSTER KNOCK SENSOR (RIGHT SIDE OF ENGINE) LOCK OFF LT BLU WIRE LT GRN/YEL WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR NCA WIRE ORG/ WIRE PNK PPL WIRE PNK WIRE PNK/BLK WIRE PPL 3 4 PPL/WHT WIRE PROVISIONS FOR TACHOMETER RED WIRE RUN WIRE TAN/BLK WIRE VEHICLE SPEED SENSOR (LEFT REAR OF TRANSMISSION) VEHICLE SPEED SENSOR BUFFER (BEHIND RIGHT SIDE OF I/P) WHT WIRE

3 121 PNK WIRE 4.3L AND 7.4L 5.7L ACCY ALT FUSE BLK WIRE BLK/RED WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (CENTER REAR OF ENGINE) DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE ENGINE COOLANT TEMPERATURE SENSOR (TOP FRONT OF ENGINE) FUSE BLOCK GRY WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START IDLE SPEED ACTUATOR CONTROL SOLENOID (NO LOCATION AVAILABLE) IGNITION COIL (TOP RIGHT REAR OF ENGINE) IGNITION SWITCH INSTRUMENT CLUSTER KNOCK SENSOR (LEFT REAR OF ENGINE, NEAR OIL PRESSURE SENDER) KNOCK SENSOR MODULE (TOP RIGHT SIDE OF ENGINE) LOCK OFF LT BLU/WHT WIRE LT GRN WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR MANIFOLD ABSOLUTE PRESSURE SENSOR (ABOVE VALVE COVER) NCA WIRE ORG/ WIRE PNK 26 27 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 2 3 4 PPL 24 25 PPL/WHT WIRE PROVISIONS FOR TACHOMETER RED WIRE RED/BLK WIRE RUN WIRE TAN/BLK WIRE TCC/BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) THROTTLE POSITION SENSOR (ON THROTTLE BODY) TRANS FUSE WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

3 121 PNK WIRE ACCY BLK WIRE BLK/RED WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (CENTER REAR OF ENGINE) DK BLU WIRE DK GRN/WHT WIRE ENGINE COOLANT TEMPERATURE SENSOR (TOP FRONT OF ENGINE) FUSE BLOCK GAGES FUSE GRY WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START IGNITION COIL (TOP RIGHT REAR OF ENGINE) IGNITION SWITCH INSTRUMENT CLUSTER KNOCK SENSOR (LEFT REAR OF ENGINE, NEAR OIL PRESSURE SENDER) LOCK OFF LT BLU/WHT WIRE LT GRN WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR MANIFOLD ABSOLUTE PRESSURE SENSOR (ABOVE VALVE COVER) NCA WIRE ORG/ WIRE PNK 22 23 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 20 21 PPL 3 4 PPL/WHT WIRE PROVISIONS FOR TACHOMETER RED WIRE RED/BLK WIRE RUN WIRE TAN/BLK WIRE TCC/BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) THROTTLE POSITION SENSOR (ON THROTTLE BODY) TRANS FUSE WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

3 121 PNK WIRE 4.3L AND 7.4L 5.7L ACCY ALT FUSE BLK WIRE BLK/RED WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (CENTER REAR OF ENGINE) DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE ENGINE COOLANT TEMPERATURE SENSOR (TOP FRONT OF ENGINE) FUSE BLOCK GRY WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START IDLE SPEED ACTUATOR CONTROL SOLENOID (NO LOCATION AVAILABLE) IGNITION COIL (TOP RIGHT REAR OF ENGINE) IGNITION SWITCH INSTRUMENT CLUSTER KNOCK SENSOR (LEFT REAR OF ENGINE, NEAR OIL PRESSURE SENDER) KNOCK SENSOR MODULE (TOP RIGHT SIDE OF ENGINE) LOCK OFF LT BLU/WHT WIRE LT GRN WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR MANIFOLD ABSOLUTE PRESSURE SENSOR (ABOVE VALVE COVER) NCA WIRE ORG/ WIRE PNK 26 27 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 2 3 4 PPL 24 25 PPL/WHT WIRE PROVISIONS FOR TACHOMETER RED WIRE RED/BLK WIRE RUN WIRE TAN/BLK WIRE TCC/BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) THROTTLE POSITION SENSOR (ON THROTTLE BODY) TRANS FUSE WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE

3 121 PNK WIRE ACCY BLK WIRE BLK/RED WIRE BLK/YEL WIRE BRN WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (CENTER REAR OF ENGINE) DK BLU WIRE DK GRN/WHT WIRE ENGINE COOLANT TEMPERATURE SENSOR (TOP FRONT OF ENGINE) FUSE BLOCK GAGES FUSE GRY WIRE HOT AT ALL TIMES HOT IN RUN, BULB TEST OR START IGNITION COIL (TOP RIGHT REAR OF ENGINE) IGNITION SWITCH INSTRUMENT CLUSTER KNOCK SENSOR (LEFT REAR OF ENGINE, NEAR OIL PRESSURE SENDER) LOCK OFF LT BLU/WHT WIRE LT GRN WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR MANIFOLD ABSOLUTE PRESSURE SENSOR (ABOVE VALVE COVER) NCA WIRE ORG/ WIRE PNK 22 23 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 20 21 PPL 3 4 PPL/WHT WIRE PROVISIONS FOR TACHOMETER RED WIRE RED/BLK WIRE RUN WIRE TAN/BLK WIRE TCC/BRAKE SWITCH (ON BRAKE PEDAL SUPPORT BRACKET) THROTTLE POSITION SENSOR (ON THROTTLE BODY) TRANS FUSE WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE