Fuses and relays GMC Topkick (2003-2010)

The medium duty truck GMC Topkick was produced from 2003 to 2010.

Fuse Layout GMC Topkick 2003-2010

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

Fuses and relays GMC Topkick (2003-2010)

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

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