GMC 2003 GMT560 T-Series Owner's Manual page 226

Fuses Usage
1 Ignition Switch
2 Cigarette Lighter
3 ECM Ignition 1
4 Truck Body Controller
5 ALDL Connector
Warning Lamp, Ignition Relay,
Blower Motor, Motor Relay, Auxiliary
6
Relay, Power Window Relay, INT
Relay
5-70
Fuses Usage
Room Lamp, Horn, Electric Parking
7 Brake, Radio Back Up, Rear Body
Dome Lamp
8 Power Window
Exhaust Brake Back Up, Air
Suspension Dump, Differential Lock,
9 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
ID Lamp, Marker Lamp, Tail Lamp,
19
Lighted Mirror, Illumination Lamp