GMC T-Series mk3 (2003 – 2006) – fuse box diagram
Year of production: 2003, 2004, 2005, 2006
Instrument Panel Circuit Breaker and Relay Blocks
These circuit breaker and relay blocks are located on top of the instrument panel on the passenger’s side of the cab.
GMC T-Series – fuse box – instrument panel
| Number |
Circuits Protected |
| 1 |
Ignition Switch |
| 2 |
Cigarette Lighter |
| 3 |
ECM Ignition 1 |
| 4 |
Truck Body Controller |
| 5 |
ALDL Connector |
| 6 |
Warning Lamp, Ignition Relay, Blower Motor, Motor Relay, Auxiliary Relay, Power Window Relay, INT Relay |
| 7 |
Room Lamp, Horn, Electric Parking Brake, Radio Back Up, Rear Body Dome Lamp |
| 8 |
Power Window |
| 9 |
Exhaust Brake Back Up, Air Suspension Dump, Differential Lock, Air Dryer, Moisture Ejection Heater, Electric Air Compressor, Power Take Off |
| 10 |
ECM Ignition Power |
| 11 |
Trailer Turn (LH) Lamp |
| 12 |
Auxiliary (Ignition ON) |
| 13 |
Auxiliary (Battery Direct) |
| 14 |
Headlamp (LH) |
| 15 |
Headlamp (RH) |
| 16 |
Headlamp |
| 17 |
Heated Fuel |
| 18 |
Meter Truck Body Controller |
| 19 |
ID Lamp, Marker Lamp, Tail Lamp, Lighted Mirror, Illumination Lamp |
| 20 |
Cool Condenser Fan Motor, Cooler Compressor |
| 21 |
Wiper Motor, Washer Motor |
| 22 |
Heated Mirror, Two-Speed Axle Relay |
| 23 |
Empty |
| 24 |
Blower Motor, Air Conditioner Relay |
| 25 |
Trailer Turn (RH) Lamp, Flasher Unit |
| 26 |
Power Post (Consent) |
Maxi-Fuse Block
Maxi-Fuse block is located outside of the cab at the rear, on the driver’s side.
| Name |
Circuits/Circuit Breakers Protected |
| ST/TURN/HAZ |
Stoplamp, Turn Signals/Hazard Warning Flashers |
| IGN SW3 |
Air Conditioner, Axle, Chassis |
| INT/EXT LIGHTS |
Parking Lamps, Dome Lamp, Instrument Panel Lights |
| HEAD LAMP |
Headlamps, Daytime Running Lamps |
| AUX WRG |
Auxiliary, Parking Brake |
| IGN SW1 |
Ignition Switch, Washer/Wiper, Crank, Radio |
| HYD PUMP |
Hydraulic Brake, Brake Pump Motor |
| ABS |
Anti-Lock Brake System Module |
| ELECT TRANS |
Ignition Relay |
| PARK BRAKE |
Parking Brake Motor |
| BLOWER HORN |
Blower, Horn, Cigarette Lighter, Auxiliary |
| TRAILER ABS |
Trailer Anti-Lock Brake System, Trailer Stoplamps |
| PWR WDO/LOCKS |
Power Windows, Power Door Locks |
Relay Blocks
There are three relay blocks in your vehicle.
GMC T-Series – fuse box – relay blocks
| Relay |
Relay block |
| A |
Relay Block A |
| B |
Relay Block B |
| C |
Relay Block C |
Relay Block A
GMC T-series – fuse box – relay block A
| Relay Block A |
Usage |
| 1 |
Power Window |
| 2 |
Back Lamp (Reverse) |
| 3 |
High Beam |
| 4 |
Lighting |
| 5 |
Lighting (Low, High) |
| 6 |
Trailer Turn Signal (Left Headlamp) |
| 7 |
Tail Lamp |
| 8 |
Marker Lamp |
| 9 |
Trailer Turn Signal (Right Headlamp) |
Relay Block B
GMC T-Series – fuse box – relay block B
| Relay Block B |
Usage |
| 1 |
Air Conditioning Condenser |
| 2 |
Air Conditioning Compressor |
| 3 |
Heater Fan |
| 4 |
Ignition Accessory |
| 5 |
Ignition 1 |
| 6 |
Ignition 2 |
| 7 |
Auxiliary |
| 8 |
Horn |
| 9 |
Ignition 3 |
| 10 |
Dome Lamp |
| 11 |
Exhaust Brake |
| 12 |
Power Take Off Control |
Relay Block C
GMC T-series – fuse box – relay block C
| Relay Block C |
Usage |
| 1 |
Parking Brake |
| 2 |
Daytime Running Lamps On |
| 3 |
Daytime Running Lamp Off |
| 4 |
Parking Lamps/Daytime Running Lamps |
| 5 |
Neutral |
| 6 |
Stop Lamp |
WARNING: Terminal and harness assignments for individual connectors will vary depending on vehicle equipment level, model, and market.
