Find GMC Topkick fuse box diagrams and electrical details in this straightforward guide. In this article, we cover the medium-duty GMC Topkick, available from 2003 to 2009 , with fuse box diagrams for GMC Topkick 2003, 2004, 2005, 2006, 2007, 2008 and 2009 , plus clear information on the location of the fuse panels and the assignment of each fuse and relay (fuse layout).
There are two fuse box located behind the instrument panel on the passenger’s side of the vehicle.
Both fuse box are located in the engine compartment, on the passenger’s side of the vehicle.
Assignment of the fuses in the Primary Under-hood Fuse Block (2003-2006)
Fuse Data
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Short-Code Description RR DEFOG Rear Defog ENG 1 Engine 1 ENG 3 Engine 3 PCM-B Powertrain Control Module BLANK Not Used ENG 4 Engine 4 ENG 2 Engine 2 HTD FUEL Heated Fuel BLANK Not Used BLANK Not Used O2A Emissions A/C COMP Air Conditioning Compressor ABS 1 Anti-lock Brake System 1 ABS 2 Anti-lock Brake System 2 ABS 3 Anti-lock Brake System 3 ENGINE Engine E/A PUMP Electronic/Automatic Pump HORN Horn NOTE 2 L18 Fuel, LG4 Powertrain Control Valve, LG5 Electronic Control Module NOTE 3 L18 Fuel, LG4 Powertrain Control Valve, LG5 Electronic Control Module STUD A Spare STUD B Spare
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Assignment of the relays in the Primary Under-hood Fuse Block (2003-2006)
Fuse Data
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Short-Code Description NOTE 1 LG4 Powertrain Control Valve, L18 Fuel Pump, LG5 Heated Fuel IGN B Ignition STARTER Starter HORN Horn IGN A Ignition PTO/ECU Power Take-Off/Engine Control Unit “Diesel 7.8L DURAMAX REVERSE Reverse NEUTRAL START Neutral Start
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Assignment of the fuses in the Secondary Under-hood Fuse Block (2003-2006)
Fuse Data
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Short-Code Description IGN 1 Four-Wheel Drive Module IGN 4 Ignition 4 IGN 3 Ignition 3 BATT/HAZ Battery/Hazard Warning Flashers HEADLAMP Headlamps LIGHTING Interior/Exterior Lamps HVAC Climate Control System NOTE C4/C5 Electric Brake, C6/C7/C8 Brake Lamps
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Assignment of the fuses in the Instrument panel fuse box 1 (2003-2006)
Fuse Data
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No. Description 1 Stoplamps 2 Center High-Mounted Stoplamp 3 Parking Lamps 4 Powertrain Control Module 5 Auxiliary Wiring 6 Heater/Air Conditioning 7 Hazard Warning Flashers 8 Power Post 9 Courtesy Lamps 10 Warning Lights, Gages and Indicators 11 Starter 12 Rear Axle/Four-Wheel-Drive 13 Trailer Turn Signals/Hazard Warning Flashers 14 Radio/Chime 15 Daytime Running Lamps 16 Airbag System 17 Exterior/lnterior Lamps 18 Parking Brake 19 Accessory Power 20 Ignition 4 21 Sidemarker Lamps 22 Turn Signal/Backup Lamps 23 Transmission 24 Hydraulics/Air Brake A Spare B Spare
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Assignment of the fuses in the Instrument panel fuse box 2 (2003-2006)
Fuse Data
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Short-Code Description HTD/MIRR Heated Mirrors Blank Not Used RT TRN TRLR Passenger’s Side Trailer Turn Signal Blank Not Used LT TRN TRLR Driver’s Side Trailer Turn Signal Blank Not Used BRK Brake Warning Lamp RT PRK Passenger’s Side Parking Lamps Blank Not Used Blank Not Used Blank Not Used LT PARK Driver’s Side Parking Lamps Blank Not Used RT REAR TRN/STOP Passenger’s Side Rear Turn Signal/Stoplamp LT REAR TRN/STOP Driver’s Side Rear Turn Signal/Stoplamp RADIO Radio Blank Not Used Blank Not Used Blank Not Used PWR WNDW Power Windows
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Assignment of the relays in the Instrument panel fuse box 2 (2003-2006)
Fuse Data
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Short-Code Description ECU/PTO Engine Control Unit/Power Take-Off “Diesel 7.8 DURAMAX® BRK LAMP C4/C5 Brake Lamps, C6/C7/C8 Tractor/Trailer Wiring DRL Daytime Running Lamps IGN-4 Ignition CHMSL Center High Mounted Stop Lamp MRK LTS Sidemarker and Clearance Lamps
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Assignment of the fuses in the Primary Under-hood Fuse Block (2007)
Fuse Data
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Short-Code Description RR DEFOG Rear Defog ENG 1 Engine 1 ENG 3 Engine 3 PCM-B Powertrain Control Module BLANK Not Used ENG 4 Engine 4 ENG 2 Engine 2 HTD FUEL Heated Fuel BLANK Not Used BLANK Not Used O2A Emissions A/C COMP Air Conditioning Compressor ABS 1 Anti-lock Brake System 1 ABS 2 Anti-lock Brake System 2 ABS 3 Anti-lock Brake System 3 ENGINE Engine E/A PUMP Electronic/Automatic Pump HORN Horn NOTE 2 L18 Fuel, LG4 Powertrain Control Valve, LG5 Electronic Control Module NOTE 3 L18 Fuel, LG4 Powertrain Control Valve, LG5 Electronic Control Module STUD A Spare STUD B Spare
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Assignment of the relays in the Primary Under-hood Fuse Block (2007)
Fuse Data
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Short-Code Description NOTE 1 LG4 Powertrain Control Valve, L18 Fuel Pump, LG5 Heated Fuel IGN B Ignition STARTER Starter HORN Horn IGN A Ignition PTO/ECU Power Take-Off/Engine Control Unit ‘Diesel 7.8L DURAMAX’ REVERSE Reverse NEUTRAL START Neutral Start
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Assignment of the fuses in the Secondary Underhood Fuse Block (2007)
Fuse Data
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No. Description 1 Four-Wheel Drive Module 2 Ignition 4 3 Ignition 3 4 Battery/Hazard Warning Flashers 5 Headlamps 6 Interior/Exterior Lamps 7 Climate Control System 8 C4/C5 Electric Brake, C6/C7/C8 Brake Lamps
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Assignment of the fuses in the Instrument panel fuse box #1 (2007)
Fuse Data
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No. Description 1 Stoptamps 2 Center High-Mounted Stoplamp 3 Parlang Lamps 4 Powertrain Control Module 5 Auxiliary Wiring 6 Heater/Air Conditioning 7 Hazard Warning Flashers 8 Power Post 9 Courtesy Lamps 10 Warning Lights, Gages and Indicators 11 Starter 12 Rear Axle/Four-Wheel-Drive 13 Trailer Turn Signals/Hazard Warning Flashers 14 Radio/Chime 15 Daytime Running Lamps 16 Airbag System 17 Exterior/Interior Lamps 18 Parlang Brake 19 Accessory Power 20 Ignition 4 21 Sidemarker Lamps 22 Turn Signal/Backup Lamps 23 Transmission 24 Hydraulics/Air Brake A Spare B Spare
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Assignment of the fuses in the Instrument panel fuse box #2 (2007)
Fuse Data
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Short-Code Description Blank Not Used RT PRK Passenger’s Side Parking Lamps Blank Not Used Blank Not Used LT PARK Driver’s Side Pairing Lamps RT REAR TRN/STOP Passenger’s Side Rear Turn Signal/Stoplamp LT REAR TRN/STOP Driver’s Side Rear Turn Signal/Stoplamp RADIO Radio Blank Not Used Blank Not Used PWRWNDW Power Windows
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Assignment of the relays in the Instrument panel fuse box 2 (2007)
Fuse Data
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Short-Code Description ECU/PTO Engine Control Unit/Power Take-Off ‘Diesel 7.8 DURAMAX BRK LAMP C4/C5 Brake Lamps, C6/C7/C8 Tractor/Trailer Wiring DRL Daytime Running Lamps IGN-4 Ignition CHMSL Center High Mounted Stop Lamp MRKLTS Sidemarker and Clearance Lamps HTD/MIRR Heated Mirrors HTR Diesel Heated Fuel RT TRN TRLR Passenger’s Side Trailer Turn Signal Blank Not Used LT TRN TRLR Driver’s Side Trailer Turn Signal Blank Not Used Blank Not Used Blank Not Used
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Assignment of the fuses in the Primary Under-hood Fuse Block (2008, 2009)
Fuse Data
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Name Usage RR DEFOG Rear Defog ENG 1 Engine 1 ENG 3 Engine 3 (L18/LF6/LF8) PCM-B Powertrain Control Module TCM Transmissions (LF8) ENG 4 Engine 4 (LMM/LF6/LF8) ENG 2 Engine 2 (L18/LMM) HTD FUEL Heated Fuel (LMM) BLANK Not Used BLANK Not Used NOTE 3 Fan Relay (LMM), Emissions (L18) A/C COMP Air Conditioning Compressor ABS 1 Anti-lock Brake System 1 ABS 2 Anti-lock Brake System 2 ABS 3 Anti-lock Brake System 3 ENGINE Engine E/A PUMP Electronic/Automatic Pump HORN Horn NOTE 2 Fuel (L18/LMM), Electronic Control Module (LF6) NOTE 3 Electronic Control Module (LF6) STUD A Spare STUD B Spare
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Assignment of the relays in the Primary Under-hood Fuse Block (2008, 2009)
Fuse Data
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Short-Code Description NOTE 1 LMM/L18 Fuel Pump Relay IGN B RELAY Ignition Relay STARTER RELAY Starter Relay HORN RELAY Horn Relay IGN A RELAY Ignition Relay PTO/ECU RELAY Power Take-Off/Engine Control Unit (*Diesel 7.8L LF8) REVERSE RELAY Reverse Relay FAN RELAY Fan Relay (LMM)
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Assignment of the fuses in the Secondary Under-hood Fuse Block (2008, 2009)
Fuse Data
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No. Description 1 Ignition 1 2 Ignition 4 3 Ignition 3 4 Battery/Hazard Warning Flashers 5 Headlamps 6 Interior/Exterior Lamps 7 Climate Control System 8 C4/C5 Electric Brake, C6/C7/C8 Brake Lamps
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Assignment of the fuses in the Instrument panel fuse box 1 (2008, 2009)
Fuse Data
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No. Description 1 Stoplamps 2 Not Used 3 Parking Lamps 4 Powertrain Control Module 5 Auxiliary Wiring 6 Heater/Air Conditioning 7 Hazard Warning Flashers 8 Power Post 9 Courtesy Lamps 10 Warning Lights, Gages and Indicators 11 Starter 12 Rear Axle/Four-Wheel-Drive 13 Trailer Turn Signals/Hazard Warning Flashers 14 Radio/Chime 15 Daytime Running Lamps 16 Airbag System 17 Exterior/lnterior Lamps 18 Parking Brake 19 Accessory Power 20 Ignition 4 21 Sidemarker Lamps 22 Turn Signal/Backup Lamps 23 Transmission 24 Hydraulics/Air Brake A Spare B Spare
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Assignment of the fuses in the Instrument panel fuse box 2 (2008, 2009)
Fuse Data
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Short-Code Description Blank Not Used RT PRK Passenger’s Side Parking Lamps Blank Not Used Blank Not Used LT PARK Driver’s Side Parking Lamps RT REAR TRN/STOP Passenger’s Side Rear Turn Signal/Stoplamp LT REAR TRN/STOP Driver’s Side Rear Turn Signal/Stoplamp RADIO Radio Blank Not Used Blank Not Used PWR WNDW Power Windows
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Assignment of the relays in the Instrument panel fuse box 2 (2008, 2009)
Fuse Data
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Short-Code Description ECU/PTO Engine Control Unit/Power Take-Off “Diesel 7.8 DURAMAX® BRK LAMP C4/C5 Brake Lamps, C6/C7/C8 Tractor/Trailer Wiring DRL Daytime Running Lamps IGN-4 Ignition CHMSL Center High Mounted Stop Lamp MRK LTS Sidemarker and Clearance Lamps HTD/MIRR Heated Mirrors HTR Diesel Heated Fuel RT TRN TRLR Passenger’s Side Trailer Turn Signal Blank Not Used LT TRN TRLR Driver’s Side Trailer Turn Signal Blank Not Used Blank Not Used Blank Not Used
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