The GMC Topkick medium-duty truck was produced from 2003 to 2010. In this article you will find the 2006, 2007, 2008 and 2009 GMC Topkick fuse box diagrams, information on the location of the fuse boxes in the vehicle and the assignment of each fuse (fuse layout) and relay.
Fuse box location
Instrument panel fuse box
There are two instrument panel fuse blocks located behind the instrument panel on the passenger’s side of the vehicle.
Engine compartment fuse box
Both underhood fuse blocks are located in the engine compartment, on the passenger’s side of the vehicle.
To access the fuse blocks, gently squeeze both sides of the cover to unlatch the tabs at the top. Then, unsnap both attachments at the bottom and remove the cover.
Fuse box diagrams
2006
Primary Underhood Fuse Block
Assignment of the fuses in the Primary Underhood Fuse Block (2006)
| Name | Usage |
|---|---|
| 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 |
| Relay | |
| 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 |
Secondary Underhood Fuse Block
Assignment of the fuses in the Secondary Underhood Fuse Block (2006)
| Name | Usage |
|---|---|
| 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 |
Instrument panel, box1
Assignment of the fuses in the Instrument panel fuse box 1 (2006)
| Circuit Breaker | Usage |
|---|---|
| 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 |
Instrument panel, box 2
Assignment of the fuses in the Instrument panel fuse box 2 (2006)
| Name | Usage |
|---|---|
| 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 |
| Relay | |
| 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 |
2007
Primary Underhood Fuse Block
Assignment of the fuses in the Primary Underhood Fuse Block (2007)
| Name | Usage |
|---|---|
| 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 |
| Relay | |
| 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 |
Secondary Underhood Fuse Block
Assignment of the fuses in the Secondary Underhood Fuse Block (2007)
| Name | Usage |
|---|---|
| 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 |
Instrument panel, box1
Assignment of the fuses in the Instrument panel fuse box 1 (2007)
| Circuit Breaker | Usage |
|---|---|
| 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 |
Instrument panel, box 2
Assignment of the fuses in the Instrument panel fuse box 2 (2007)
| Name | Usage |
|---|---|
| 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 |
| Relay | |
| 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 |
2008, 2009
Primary Underhood Fuse Block
Assignment of the fuses in the Primary Underhood Fuse Block (2008, 2009)
| 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 |
| Relay | |
| 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) |
Secondary Underhood Fuse Block
Assignment of the fuses in the Secondary Underhood Fuse Block (2008, 2009)
| Name | Usage |
|---|---|
| IGN 1 | Ignition 1 |
| 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 |
Instrument panel, box 1
Assignment of the fuses in the Instrument panel fuse box 1 (2008, 2009)
| Circuit Breaker | Usage |
|---|---|
| 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 |
Instrument panel, box 2
Assignment of the fuses in the Instrument panel fuse box 2 (2008, 2009)
| Name | Usage |
|---|---|
| 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 |
| Relay | |
| 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 |
