GMC Forward Control P3500 (1985-1999) ignition switch Wiring diagrams

ABS IND. ACCY ACCY ANTI-LOCK BRAKES SYSTEM BLK WIRE BLK/WHT WIRE BRAKE IND BRAKE PRESSURE DIFFERENTIAL SWITCH (INTERNAL TO ELECTRONIC BRAKE CONROL MODULE) BRN/WHT WIRE CHECK GAUGES IND COOLANT TEMPERATURE GAUGE DIESEL DIODE NETWORK (DASH HARN, DK BLU WIRE DK GRN WIRE DOOR AJAR IND DRL IND ECM 1 FUSE 12 ELECTRONIC BRAKE CONTROL MODULE (EBCM) (BELOW RADIATOR, ON LOWER CROSSMEMBER) ENG 1 FUSE 15 ENGINE CONTROLS OR STARTING/CHARGING SYSTEM ENGINE CONTROLS SYSTEM ENGINE CONTROLS SYSTEM ENGINE CONTROLS SYSTEM TRANSMISSIONS SYSTEM ENGINE COOLANT LEVEL SWITCH (ON LOWER LEFT END OF RADIATOR SURGE TANK) FOOT BRAKE (PARK BRAKE APPLY OPPTION) FUEL GAUGE FUEL SENDER (ON TOP OF FUEL TANK) GAS GAUGES FUSE 8 GRY WIRE GRY/BLK WIRE HAND BRAKE HEADLIGHTS SYSTEM HI-BEAM IND HOT IN RUN OR START I/P FUSE BLOCK I/P FUSE BLOCK (BODY BUILDER INSTALLED) I/P FUSE BLOCK) INSTRUMENT CLUSTER IGNITION SWITCH ILLUMINATION IN-LINE CONNECTOR PROVISIONS FOR BODY BUILDER INTERIOR LIGHTS SYSTEM WARNING SYSTEMS LEFT TURN IND LOCK LOCK OFF OFF LOW COOLANT IND LT BLU WIRE LT BLU/BLK WIRE LT GRN (OR WHT) WIRE LT GRN WIRE MALFUNCTION IND (MIL) (SERVICE ENGINE SOON IND) NCA WIRE OIL PRESSURE GAUGE PNK 4 13 WIRE 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 TRANS IND. VEHICLE CONTROL MODULE (ON LEFT SIDE OF RADIATOR SUPPORT) VOLTMETER VSS CALIBRATOR (LEFT SIDE OF DRIVER'S ISLAND, UNDER RELAY BRACKET) W/ DRL W/O DRL WAIT TO START IND WATER IN FUEL IND WHT WIRE WHT/BLK WIRE YEL WIRE YEL/BLK 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

ACC RADIO FUSE ACCY BATTERY JUNCTION BLOCK BLK WIRE BODY BUILDER'S DAYTIME RUNNING LAMPS JUNCTION BLOCK RELAY BRAKE WARNING SYSTEM (WARNING SYSTEMS) BRN WIRE BULB TEST CLUTCH DAYTIME RUNNING LAMPS MODULE WIPER MOTOR DK GRN WIRE ECM BAT FUSE FROM PANEL DIMMER SWITCH FROM PARK BRAKE WARNING SWITCH FUEL CYCLE MODULE DAYTIME RUNNING LAMPS RELAY FUEL PUMP RELAY, FUEL PUMP/ OIL PRESSURE SWITCH FUSE BLOCK FUSE BLOCK, GLOW PLUG CONTROLLER FUSIBLE FUSIBLE LINK E GAGES FUSE SHUNT GENERATOR GRY WIRE HAZARD FLASHER HEADLIGHT SWITCH ASSEMBLY HORN RELAY HORN/DM TAIL LPS FUSE FUSE HTR FUSE IGNITION SWITCH INSTR LPS FUSE INSTRUMENT TRANSMISSION CLUSTER RANGE INDICATOR LAMP LINK A LINK B LINK C LINK D LINK F LOCK LOCK OFF OFF ORG/ WIRE PCM PNK WIRE PNK/WHT WIRE POWERTRAIN CONTROL MODULE PPL RED WIRE RIGHT FRONT BATTERY LEFT REAR BATTERY RUN WIRE SHUNT STARTER RELAY STARTER SOLENOID STOP- HZ FUSE STOPLAMP SWITCH SWITCH TAN/WHT WIRE TO GLOW PLUG CONTROLLER W/ AUTO TRANSMISSION W/ MANUAL TRANSMISSION ONLY PPL WHT WIRE WIPER FUSE WIPER SWITCH

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/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 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 25 26 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 2 3 4 PPL 23 24 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 5.7L ACCY ALT FUSE BLK WIRE BLK/RED WIRE BLK/WHT WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (TOP REAR OF ENGINE) DK BLU WIRE DK GRN/WHT WIRE 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 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) KNOCK SENSOR MODULE (TOP RIGHT SIDE OF ENGINE) LOCK OFF LT GRN/BLK WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR NCA WIRE ORG/ WIRE OXYGEN SENSOR (IN EXHAUST MANIFOLD) HEATED OXYGEN SENSOR (IN EXHAUST MANIFOLD) PNK PPL PPL WIRE PNK WIRE PNK/BLK WIRE PPL 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/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 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 25 26 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 2 3 4 PPL 23 24 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 5.7L ACCY ALT FUSE BLK WIRE BLK/RED WIRE BLK/WHT WIRE BRN/WHT WIRE BULB TEST DISTRIBUTOR (TOP REAR OF ENGINE) DK BLU WIRE DK GRN/WHT WIRE 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 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) KNOCK SENSOR MODULE (TOP RIGHT SIDE OF ENGINE) LOCK OFF LT GRN/BLK WIRE MALFUNCTION (SERVICE ENGINE SOON) INDICATOR NCA WIRE ORG/ WIRE OXYGEN SENSOR (IN EXHAUST MANIFOLD) HEATED OXYGEN SENSOR (IN EXHAUST MANIFOLD) PNK PPL PPL WIRE PNK WIRE PNK/BLK WIRE PPL 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/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 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 25 26 WIRE PNK WIRE PNK/BLK WIRE PPL PPL 2 3 4 PPL 23 24 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