GMC Forward Control P3500 (1985-1999) engine controls system Wiring diagrams

1-2 SHIFT SOL 1-2 SHIFT SOLENOID 2-3 SHIFT SOL 2-3 SHIFT SOLENOID 4.3L (VIN W), 5.7L (VIN R) A/C COMPRESSOR RELAY, GENERATOR, SEAT BELT/ HEADLAMPS ALARM MODULE A/T FLUID PRESSURE MANUAL VALVE POSITION SWITCH A/T ISS HI IN A/T ISS LO IN ANTI-LOCK BRAKES, CRUISE CONTROL, SHIFT INTERLOCK SYSTEMS AUTOMATIC TRANSMISSION BATTERY IN BLK WIRE BLK/WHT WIRE BLU/WHT WIRE BRAKE SWITCH INPUT BRN WIRE BRN/WHT WIRE DATA CLASS II DK BLU 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 GAUGES FUSE 8 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 THROTTLE POSITION SENSOR (ON THROTTLE BODY) TP SENS INPUT TRANS FLUID TEMP SENSOR TRANS FUSE 17 TRANS TEMP SIG IN 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 4.3L (VIN W), 5.7L (VIN R) A/C COMPRESSOR RELAY, GENERATOR, SEAT BELT/ HEADLAMPS ALARM MODULE A/T FLUID PRESSURE MANUAL VALVE POSITION SWITCH A/T ISS HI IN A/T ISS LO IN ANTI-LOCK BRAKES, CRUISE CONTROL, SHIFT INTERLOCK SYSTEMS AUTOMATIC TRANSMISSION BATTERY IN BLK WIRE BLK/WHT WIRE BLU/WHT WIRE BRAKE SWITCH INPUT BRN WIRE BRN/WHT WIRE DATA CLASS II DK BLU 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 GAUGES FUSE 8 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 THROTTLE POSITION SENSOR (ON THROTTLE BODY) TP SENS INPUT TRANS FLUID TEMP SENSOR TRANS FUSE 17 TRANS TEMP SIG IN 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

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

0.5 WATT) 1995 VFTC BLK WIRE BLK/YEL WIRE BRAKE IND BRAKE PRESSURE WARNING SWITCH (ON LEFT FRAME RAIL) IGNITION SWITCH BRAKE WARNING ALARM BUZZER (BEHIND LEFT SIDE OF I/P, NEAR FUSE BLOCK) BRN WIRE BRN/WHT WIRE COOLANT TEMP GAUGE CRUISE CONTROL SYSTEM DAYTIME RUNNING LAMPS IND DAYTIME RUNNING LAMPS MODULE (BEHIND LEFT SIDE OF I/P, ABOVE STEERING COLUMN) DAYTIME RUNNING LAMPS RELAY (BEHIND LEFT SIDE OF I/P, ABOVE STEERING COLUMN) DK BLU WIRE DK GRN WIRE DK GRN/YEL WIRE ELECTRONIC DELAY MODULE (BEHIND LEFT SIDE OF I/P, ON PARK BRAKE SUPPORT BRACKET) ENGINE CONTROLS SYSTEM FLOW SWITCH (NEAR POWER STEERING PUMP) FUEL GAUGE FUSE BLOCK GAGES FUSE GRY WIRE HEADLIGHTS SYSTEM HI-BEAM IND HOT IN RUN OR START HYDRO-BOOST PRESSURE WARNING SWITCH (NEAR MASTER CYLINDER) ILLUM LAMP ILLUM. LAMPS IN-LINE DIODE (BEHIND LEFT SIDE OF I/P, ABOVE FUSE BLOCK) IN-LINE DIODE (BEHIND LEFT SIDE OF I/P, ABOVE STEERING COLUMN) INSTRUMENT CLUSTER LEFT TURN IND LOW COOLANT IND LT BLU WIRE LT BLU/BLK WIRE LT GRN WIRE LT GRN/BLK WIRE MAL- FUNCTION IND OIL PRESS GAUGE PARK BRAKE WARNING SWITCH PNK PNK WIRE PNK WIRE PNK/BLK WIRE POWERTRAIN CONTROL MODULE (UNDER DRIVER'S SEAT) PPL RESISTOR RIGHT TURN IND SAFETY BELT IND SPEED- OMETER TAN WIRE TAN/WHT WIRE VEHICLE SPEED SENSOR (REAR OF TRANSMISSION) VEHICLE SPEED SENSOR BUFFER (BEHIND LEFT SIDE OF I/P) VOLT- METER W/ DRL W/ DRL PPL PPL W/O DRL WARNING SYSTEMS WHT WIRE YEL WIRE

1995 VFTC ACCY ALT FUSE AUDIO ALARM MODULE CONVENIENCE CENTER BLK WIRE BRAKE IND BRAKE PRESSURE WARNING SWITCH (NEAR MASTER CYLINDER) BRAKE WARNING ALARM BUZZER MODULE (BRAKE WARNING HARNESS) BRN WIRE BRN/WHT WIRE BULB TEST COOLANT TEMP GAUGE DAYTIME RUNNING LAMPS MODULE (TOP RIGHT SIDE OF SHIPPING HARNESS) DAYTIME RUNNING LAMPS RELAY DAYTIME RUNNING LIGHTS IND DK BLU WIRE DK BLU/WHT WIRE DK GRN WIRE DK GRN/YEL WIRE ELECTRONIC DELAY MODULE (BRAKE WARNING HARNESS) ENGINE CONTROLS SYSTEM ENGINE COOLANT TEMPERATURE SENDER (LEFT FRONT OF ENGINE) FLOW SWITCH (BRAKE BOOSTER) FUEL GAUGE FUEL PUMP OIL PRESSURE SWITCH, SENDER (TOP REAR OF ENGINE) FUEL PUMP, SENDER (IN FUEL TANK) FUSE BLOCK GAUGES FUSE GRY WIRE HEAD- LIGHTS SYSTEM HEADLIGHTS SYSTEM HI-BEAM IND HOT IN RUN OR START HOT IN RUN, BULB TEST OR START HYDRO-BOOST PRESSURE WARNING SWITCH (BRAKE WARNING HARNESS) I/P GROUND (AT LEFT SHIPPING PANEL) IGNITION SWITCH ILLUM. LAMPS INSTRUMENT CLUSTER LEFT TURN IND LOCK OFF LT BLU WIRE LT BLU/BLK WIRE LT GRN WIRE LT GRN/BLK WIRE MAL- FUNCTION IND NCA WIRE OIL PRESS GAUGE PARK BRAKE IND PARK BRAKE WARNING SWITCH (PARK BRAKE PEDAL BRACKET) PNK PPL WIRE PNK WIRE PNK/BLK WIRE POWERTRAIN CONTROL MODULE (LEFT SIDE OF I/P, BEHIND SHIPPING PANEL) PPL RESISTOR RIGHT TURN IND. SAFETY BELT IND. RUN WIRE SHUNT SPEED- OMETER TAN WIRE TAN/WHT WIRE VEHICLE SPEED SENSOR (REAR OF TRANSMISSION) VEHICLE SPEED SENSOR BUFFER (LEFT SIDE OF SHIPPING PANEL) VOLT- METER W/ DRL W/O DRL WHT WIRE YEL WIRE

4 13 PNK WIRE A/T ABS IND. ACCY BULB TEST LOCK OFF ANTI-LOCK BRAKES SYSTEM AUTO PARK IND. BLK WIRE BLK/WHT WIRE BRAKE IND DRL IND BRN/WHT WIRE CHECK GAUGES IND COOLANT TEMPERATURE GAUGE DIESEL DK BLU WIRE DK GRN WIRE DOOR AJAR IND ECM 1 FUSE 12 ENGINE CONTROLS OR STARTING/ CHARGING SYSTEM ENGINE CONTROLS SYSTEM ENGINE CONTROLS SYSTEM ENGINE CONTROLS SYSTEM ENGINE COOLANT LEVEL SWITCH (ON LOWER LEFT END OF RADIATOR SURGE TANK) FUEL GAUGE FUEL SENDER (ON TOP OF FUEL TANK) GAS GAUGES FUSE 8 GRY WIRE GRY/BLK WIRE HEADLIGHTS SYSTEM HI-BEAM IND HOT IN RUN OR START I/P FUSE BLOCK (BEHIND DASH PANEL) (BODY BUILDER INSTALLED) IGNITION SWITCH ILLUMINATION IN-LINE CONNECTOR PROVISIONS FOR BODY BUILDER INSTRUMENT CLUSTER INTERIOR LIGHTS SYSTEM WARNING SYSTEMS LEFT TURN IND LOW COOLANT IND LT BLU WIRE LT GRN (OR WHT) WIRE LT GRN WIRE LT GRN/BLK WIRE MALFUNCTION IND. LAMP (MIL) (SERVICE ENGINE SOON IND) OIL PRESSURE GAUGE PNK WIRE PPL PPL DIESEL PPL GAS PPL RIGHT TURN IND RUN WIRE SEAT BELT IND SERVICE THROTTLE SOON IND SPEEDOMETER TACHOMETER TAN WIRE TAN/WHT WIRE VEHICLE CONTROL MODULE (ON LEFT SIDE OF RADIATOR SUPPORT) VOLTMETER VSS CALIBRATOR (LEFT SIDE OF DRIVER'S ISLAND, UNDER RELAY BRACKET) WAIT TO START IND WATER IN FUEL IND WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK WIRE