GMC Pickup C2500 (1985-2000) underhood fuse-relay center Wiring diagrams

1827 33 VSS SIG IND OUT SERIAL DATA LINE ABS FUSE ABS IND. BLK WIRE BLK/WHT WIRE BRAKE FUSE 18 BRAKE IND BRAKE SW OUTPUT BRN WIRE DAYTIME RUNNING LAMPS MODULE (LEFT SIDE OF DASH) DK GRN WIRE EBCM GROUND ELECTRONIC BRAKE CONTROL MODULE (LEFT SIDE OF ENGINE COMPT) HOT AT ALL TIMES HOT IN RUN HOT IN RUN, BULB TEST OR START GAUGES FUSE 4 I/P FUSE BLOCK IGN ABS LAMP CONTROL BRAKE SW INPUT INSTRUMENT CLUSTER LEFT FRONT WHEEL SPEED SENSOR LFT FRT SENSOR (-) LT BLU WIRE LT GRN WIRE LT GRN/BLK WIRE PNK WIRE PPL PPL/WHT WIRE PUMP MOTOR POWER PUMP MOTOR GROUND RED WIRE RIGHT FRONT WHEEL SPEED SENSOR RT FRT SENSOR (-) LFT FRT SENSOR (+) RT FRT SENSOR (+) TAN WIRE TAN/WHT WIRE TCC/ STOPLAMP SWITCH (TOP OF BRAKE PEDAL) UNDERHOOD FUSE-RELAY CENTER VEHICLE CONTROL MODULE (LEFT SIDE OF ENGINE COMPT) VEHICLE SPEED SENSOR (LEFT SIDE OF TRANSMISSION/ TRANSFER CASE) VEHICLE SPEED SIG VSS YEL WIRE YEL/BLK WIRE

A/T ONLY ABS FUSE ABS IND. BLK WIRE BLK/WHT WIRE BRAKE FUSE 18 BRAKE IND BRAKE PRESSURE WARNING SWITCH BRN WIRE DAYTIME RUNNING LAMPS MODULE (BEHIND LEFT SIDE OF DASH) DIODE 1 (UNDERHOOD FUSE/RELAY CENTER) DK GRN WIRE ELECTRONIC BRAKE CONTROL MODULE (LEFT SIDE OF ENGINE COMPT) FRONT AXLE ACTUATOR (RIGHT FRONT OF DRIVE AXLE) HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START GAUGES FUSE 4 I/P FUSE BLOCK IGN ABS LAMP CONTROL BRAKE SW INPUT INPUT INSTRUMENT CLUSTER LEFT FRONT WHEEL SPEED SENSOR LFT FRT SENSOR (-) LT BLU WIRE LT GRN WIRE PNK WIRE PPL PPL PPL PUMP MOTOR POWER PUMP MOTOR GROUND RED WIRE RIGHT FRONT WHEEL SPEED SENSOR RT FRT SENSOR (-) LFT FRT SENSOR (+) RT FRT SENSOR (+) TAN WIRE TAN/WHT WIRE TCC/ STOPLAMP SWITCH (TOP OF BRAKE PEDAL) UNDERHOOD FUSE-RELAY CENTER VEHICLE SPEED SENSOR BUFFER (BEHIND RIGHT SIDE OF DASH) VSS SIG OUT VSS SIG SERIAL DATA LINE SERIAL DATA SIGNAL BRAKE LAMP CONTROL EBCM GROUND YEL WIRE YEL/BLK WIRE

1 2 3 4 5 6 7 8 9 10 ILLUMINATION GROUND A/C DISABLE AUX FAN CTRL IGNITION A/C COMPRESSOR CLUTCH A/C COMPRESSOR CLUTCH CYCLING SWITCH (IN LOW PRESSURE LINE NEAR COMPRESSOR) A/C COMPRESSOR CLUTCH RELAY (IN UNDERHOOD FUSE/RELAY CENTER) A/C CTRL A/C HIGH PRESSURE CUTOUT SWITCH (AT A/C COMPRESSOR) A/C MAXI FUSE 3 CENTER A/C REQ AUX FAN MINI FUSE AUXILIARY COOLING FAN A/C PRESSURE SWITCH AUXILIARY COOLING FAN MOTOR AUXILIARY COOLING FAN RELAY (7.4L VIN J) (IN UNDERHOOD FUSE/RELAY CENTER) BATTERY IGNITION GROUND DEFOGGER ELEMENT BLK WIRE BLOWER MOTOR BLOWER RESISTOR (UNDER RIGHT SIDE OF I/P, ON HEATER HOUSING) BLOWER SWITCH BRN WIRE DIODE DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE GAS DIESEL GRY WIRE GRY/BLK WIRE HEATER AND A/C CONTROL MODULE HIGH BLOWER RELAY (UNDER I/P ON TOP OF HEATER-A/C CASE) HOT AT ALL TIMES HOT IN RUN HOT IN RUN OR START IGN MINI FUSE A/C COMP MINI FUSE HOT IN RUN, BULB TEST OR START FUSE BLOCK HTR A/C FUSE 12 IGN E MINI FUSE LT BLU WIRE LT GRN WIRE NCA WIRE OFF LO ORG/ WIRE PNK WIRE PPL REAR DEFOGGER SYSTEM RECIRCULATION DOOR MOTOR (UNDER I/P ON HEATER- A/C CASE) RED WIRE TAN WIRE UNDERHOOD FUSE-RELAY UNDERHOOD FUSE-RELAY CENTER VALVE CTRL AIR TEMP DR SENSOR MODE SIGNAL A/C SWITCH WATER VALVE (SUBURBAN, UTILITY, CREW CAB ONLY) (RIGHT CENTER OF INTAKE AREA) WHT WIRE YEL WIRE

1 2 3 4 5 6 7 8 9 10 ILLUMINATION GROUND A/C MAXI FUSE 3 AIR TEMP DR SENSOR MODE SIGNAL BATTERY IGNITION GROUND DEFOGGER ELEMENT BLK WIRE BLOWER MOTOR BLOWER RESISTOR (UNDER RIGHT SIDE OF I/P, ON HEATER HOUSING) BLOWER SWITCH BRN WIRE DK BLU WIRE DK GRN WIRE FRONT MODE DOOR MOTOR (UNDER I/P ON HEATER- A/C CASE) FRONT TEMPERATURE DOOR MOTOR (UNDER I/P ON HEATER- A/C CASE) FUSE BLOCK GRY WIRE HEATER AND A/C CONTROL MODULE HIGH BLOWER RELAY (UNDER I/P ON TOP OF HEATER-A/C CASE) HOT IN RUN HTR A/C FUSE 12 LT BLU WIRE OFF LO ORG/ WIRE PPL REAR DEFOGGER SYSTEM RECIRC CTRL IGNITION RECIRCULATION DOOR MOTOR (UNDER I/P ON HEATER- A/C CASE) RED WIRE TAN WIRE UNDERHOOD FUSE-RELAY CENTER WHT WIRE YEL WIRE

& CRUISE FUSES A/T M/T AUX FAN MINI FUSE AUXILIARY COOLING FAN RELAY BLK WIRE BLK/RED WIRE BRAKE LAMP RELAY BRAKE PRESSURE MODULATOR VALVE BRN WIRE CRANK FUSE 8 DIAGNOSTIC ENERGY RESERVE MODULE FUEL PUMP RELAY FUSIBLE HEATER-A/C CONTROL I/P FUSE BLOCK IGNITION SWITCH INSTRUMENT CLUSTER LEFT RIGHT BATTERY BATTERY LINK LOCK LOCK OFF MAXI FUSE MAXI FUSE 2 MAXI FUSE 4 MAXI FUSE 5 MAXI FUSE 6 MAXI FUSE 7 MAXI FUSE 8 NCA WIRE OFF ORG/ WIRE PNK WIRE PPL RED WIRE REMOTE BATTERY STUD RR-DEFOG MINI FUSE RUN WIRE STARTER GENERATOR MOTOR SOLENOID TO BLOWER RELAYS TO CTSY, PK LPS, DRL/FOG FUSES, HEAD- LAMP SWITCH TO ECM-B, HORN, A/C COMP FUSES TO GAUGES, AIR BAG FUSES TO HTR-A/C, TO IGN-E, ECM-I, ENG-1 FUSES TO RADIO/ BATT, CIG LTR, AUX PWR FUSES, PWR ACCY BREAKER TO WIPER, RADIO, REAR WIPER FUSES TRANS FUSE 20 TRANS- MISSION TRANSMISSION CLUTCH RANGE SWITCH SWITCH UNDERHOOD FUSE-RELAY CENTER WHT WIRE YEL WIRE

A/C COMP MINI FUSE A/C LOW PRESSURE CUTOUT SWITCH AUXILIARY COOLING FAN RELAY BRN WIRE CONVENIENCE CENTER ECM-B MINI FUSE ECM-I MINI FUSE ELECTRONIC INJECTION PUMP ENG-I MINI FUSE FROM AUX FAN FUSE FROM IGNITION SWITCH FROM MAXI FUSE 6 FUEL PUMP OIL PRESSURE SWITCH/ SENDER FUEL PUMP RELAY FUEL SOL MINI FUSE GLOW PLUG RELAY HIGH BLOWER RELAY HORN MINI FUSE HORN RELAY I/P FUSE BLOCK IGN E MINI FUSE LOW BLOWER RELAY MAXI FUSE 3 MEDIUM BLOWER RELAY ORG/ WIRE PNK WIRE POWERTRAIN CONTROL MODULE (PCM) RADIO RADIO FUSE 17 REAR WIPER FUSE 23 REAR WIPER/ WASHER SWITCH RED WIRE SUBURBAN ONLY SUBURBAN, UTILITY ONLY TO POWER WINDOW CIRCUIT BREAKER UNDER HOOD FUSE-RELAY CENTER UNDERHOOD FUSE-RELAY CENTER UNDERHOOD REEL LAMP WATER EGR IN FUEL SOLENOID SENSOR VALVE WHT WIRE WIPER FUSE 11 WIPER MOTOR MODULE WIPER/ WASHER SWITCH YEL WIRE

& CRUISE FUSES A/T M/T AUX FAN MINI FUSE AUXILIARY COOLING FAN RELAY BATTERY BLK WIRE BLK/RED (OR BLK) WIRE BRAKE LAMP RELAY BRAKE PRESSURE MODULATOR VALVE BRN WIRE CRANK FUSE 8 DIAGNOSTIC ENERGY RESERVE MODULE EXCEPT 4.3L FUSIBLE HEATER-A/C CONTROL I/P FUSE BLOCK IGNITION SWITCH INSTRUMENT CLUSTER LINK LOCK LOCK OFF M/T ONLY MAXI FUSE MAXI FUSE 2 MAXI FUSE 4 MAXI FUSE 5 MAXI FUSE 6 MAXI FUSE 7 MAXI FUSE 8 NCA WIRE OFF ORG/ WIRE PNK WIRE POWERTRAIN CONTROL MODULE (PCM) PPL RED WIRE REMOTE BATTERY STUD RR-DEFOG MINI FUSE RUN WIRE STARTER GENERATOR MOTOR SOLENOID TO BLOWER RELAYS TO CTSY, PK LPS, DRL/FOG FUSES, HEAD- LAMP SWITCH TO ECM-B, HORN, A/C COMP FUSES TO GAUGES, AIR BAG FUSES TO HTR-A/C, TO IGN-E, ECM-I, ENG-1 FUSES TO RADIO/ BATT, CIG LTR, AUX PWR FUSES, PWR ACCY BREAKER TO WIPER, RADIO, REAR WIPER FUSES TRANS FUSE 20 TRANS- MISSION TRANSMISSION CLUTCH RANGE SWITCH SWITCH UNDERHOOD FUSE-RELAY CENTER WHT WIRE YEL WIRE

4.3L, 5.0L, 5.7L ONLY 5.7L W/ H/D A/T A/C COMP MINI FUSE A/C LOW PRESSURE CUTOUT SWITCH AUXILIARY FUEL COOLING CYCLE FAN CONTROL RELAY MODULE BRN WIRE CONVENIENCE CENTER ECM-B MINI FUSE ECM-I MINI FUSE EGR ELECTRONIC VACUUM REGULATOR SOLENOID ELECTRONIC HEATED SPARK OXYGEN CONTROL SENSOR MODULE ENG-I MINI FUSE EXCEPT 4.3L 5.7L H/D W/ M/T FROM AUX FAN FUSE FROM IGNITION SWITCH FROM MAXI FUSE 6 FUEL INJECTOR 1 FUEL INJECTOR 2 FUEL PUMP OIL PRESSURE SWITCH/ SENDER FUEL PUMP RELAY HIGH BLOWER RELAY HORN MINI FUSE HORN RELAY I/P FUSE BLOCK IGN E MINI FUSE LOW BLOWER RELAY M/T ONLY MAXI FUSE 3 MEDIUM BLOWER RELAY ORG/ WIRE PNK WIRE POWERTRAIN CONTROL MODULE POWERTRAIN CONTROL MODULE (PCM) RADIO RADIO FUSE 17 REAR WIPER FUSE 23 REAR WIPER/ WASHER SWITCH RED WIRE SUBURBAN ONLY SUBURBAN, UTILITY ONLY TO POWER WINDOW CIRCUIT BREAKER UNDER HOOD FUSE-RELAY CENTER UNDERHOOD FUSE-RELAY CENTER UNDERHOOD REEL LAMP WHT WIRE WIPER FUSE 11 WIPER MOTOR MODULE WIPER/ WASHER SWITCH YEL WIRE

16 PPL 6 7 8 8 9 PNK WIRE AUTOMATIC TRANSMISSION INPUT SHAFT SPEED (A/T ISS) SENSOR BALANCE FUEL PUMP (ON INSIDE LEFT FRAME RAIL NEAR FRONT OF REAR TANK) BLK (OR WIRE BLK WIRE BLK/WHT WIRE BLU WIRE BLU/WHT WIRE BRN WIRE BRN/WHT WIRE DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE FUEL PUMP BALANCE MODULE (INSIDE LEFT SIDE OF FRAME RAIL) FUEL PUMP BALANCE RELAY (ON FUEL PUMP BALANCE MODULE) FUEL PUMP, SENDER (IN FUEL TANK) FUEL PUMP/ OIL PRESSURE SWITCH (TOP CENTER REAR OF ENGINE, BEHIND DISTRIBUTOR) FUEL TANK PRESSURE SENSOR (CALIF ONLY) (IN FUEL TANK) GAUGES FUSE 4 GRN WIRE GRY WIRE HOT IN OFF, RUN OR START HOT IN RUN OR START I/P FUSE BLOCK IGN E FUSE INPUT FUEL GAUGE INPUT OIL GAUGE INPUT TACHOMETER INSTRUMENT CLUSTER INTAKE AIR TEMPERATURE SENSOR (IN AIR INTAKE DUCT) LT BLU/WHT WIRE LT GRN WIRE M/T ONLY MAP SENSOR PRESSURE (MAP) SENSOR (TOP RIGHT OF ENGINE, NEAR FUEL INJECTORS) MASS AIR FLOW SENSOR (IN AIR INTAKE DUCT) ORG/ WIRE OUTPUT TO GAUGE PNK (TAILLAMP EXTENSION HARN, 6 CM FROM THE FUEL PUMP HARN BREAKOUT) WIRE PNK IGNITION WIRE PNK PNK PNK WIRE PNK WIRE PPL PPL PPL PPL/WHT WIRE PRIMARY TANK FUEL LVL SIG RED WIRE RED/BLK WIRE RELAY CTRL SERVICE ENGINE SOON INDICATOR SPEEDOMETER INPUT TAN WIRE TAN/BLK WIRE THROTTLE POSITION SENSOR (ON THROTTLE BODY ASSEMBLY) TRANS FUSE 20 UNDERHOOD FUSE-RELAY CENTER UPSHIFT LAMP W/ DUAL FUEL TANKS W/O DUAL FUEL TANKS W/O DUAL FUEL TANKS W/ DUAL FUEL TANKS WHT (OR WIRE WHT WIRE YEL WIRE

A/C REQUEST SIGNAL AIR CONDITIONING SYSTEM AIR INLET VLV MTR CTLR BLK WIRE BLK/WHT WIRE BLU WIRE BLU/WHT WIRE BRAKE FUSE 18 BRN WIRE BRN/WHT WIRE CLUTCH PEDAL POSITION (CPP) SWITCH (AT TOP OF CLUTCH PEDAL) CPP SW INPUT FOUR WHL DR SIG LO CRUISE CTRL SIG ENG 23 24 CRUISE CONTROL MODULE (LEFT REAR OF ENGINE COMPARTMENT, ON FIREWALL) DATA LINK CONNECTOR (UNDER LEFT SIDE OF DASH) DISTRIBUTOR DK BLU WIRE DK GRN WIRE DK GRN/WHT WIRE ELECTRONIC BRAKE CONTROL MODULE (EBCM) (ON LEFT SIDE OF ENGINE COMPARTMENT) EVO/PASSLOCK STEERING CONTROL MODULE (CENTER OF DASH) FORCE MOTOR FEED TRANS INPUT SPEED RTN TRANS INPUT SPEED SIG EST OUTPUT SIG FORCE MOTOR RETURN GROUND GROUND SENSOR GROUND FUEL LEVEL INPUT SWITCH SIGNAL FUEL PUMP PRIME CONNECTOR FUEL PUMP RELAY FUEL PUMP RLY CTRL 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 GRN WIRE GROUND GRY WIRE GRY/BLK WIRE HIGH VOLTAGE COIL WIRE HOT AT ALL TIMES UNDERHOOD FUSE- RELAY CENTER ECMB FUSE HOT IN RUN I/P FUSE BLOCK IGN BRAKE INPUT INPUT INPUT DATA SW SIG INPUT IGNITION IGNITION COIL (TOP LEFT REAR OF ENGINE) IGNITION COIL DRIVER (LEFT REAR SIDE OF ENGINE) IGNITION FEED IGN TIMING SIG. IGN COIL OUT IGNITION PRESSURE SWITCH INPUT PRESSURE SWITCH INPUT LT BLU/BLK WIRE LT BLU/WHT WIRE LT VSS SERIAL ORG/ WIRE PNK IGNITION FOUR WHL DR SIG EGR VLV GROUND WIRE PNK PNK PNK WIRE PNK WIRE PPL PPL (OR PPL A/T M/T PPL PPL PPL PPL 420 OR PPL/WHT WIRE PRESSURE SWITCH INPUT RADIO RED WIRE RED/BLK WIRE SENSOR RETURN SHIFT IND LP OUT EGR VLV FEED SPEED SENSOR SPEED STOPLAMP/ VCM SENSOR CLUTCH SIG INPUT SWITCH INPUT STOPLAMP SWITCH (TOP OF BRAKE PEDAL) SWITCH SIGNAL TAN/BLK WIRE TRANSFER CASE CONTROL MODULE (UNDER DASH ON STEERING COLUMN SUPPORT BRACKET) TRANSFER CASE SWITCH (LEFT TOP OF TRANSFER CASE) TRANSMISSIONS SYSTEM (FOUR WHEEL DRIVE INDICATOR CIRCUIT UNDERHOOD FUSE-RELAY CENTER VEHICLE CONTROL MODULE (VCM) (LEFT SIDE OF ENGINE COMPT) VSS SIG OUT VSS SIG OUT CHECK ENG LP CTRL 389 419 WHT WIRE WHT/BLK WIRE