Share this

GMC T-Series mk3 (2003 - 2006) - fuse box diagram

avatar Jonathan Yarden Mar 25, 2021 · 5 min. read

In this article you will find a description of fuses and relays GMC, with photos of block diagrams and their locations. Highlighted the cigarette lighter fuse (as the most popular thing people look for).
Get tips on blown fuses, replacing a fuse, and more.

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.

Still have questions or want to supplement the article? Discuss On Telegram


Access the private club

Become a member of Fuses.guru and get access to our private telegram bot. Accelerated access and smart search of fuse box & wiring diagrams.
P.S. We never spam!

May Be Useful