The wiring circuits in your vehicle are protected from short circuits by a combination of fuses, circuit breakers, maxi-fuses and fusible links. This greatly reduces the chance of a fire caused by an electrical problem. There may be a fuse taped to the wiring harness near the hydraulic brake booster.
Instrument Panel Fuse Block
There is an instrument panel fuse block located behind the instrument panel on the passenger's side of the vehicle.
Be sure to replace fuses with fuses of the same rating. Do not use fuses of higher amperage than those indicated on the fuse block.
Circuit Breaker | Usage |
|---|---|
1 | Stoplamps |
2 | Radio |
3 | Parking Lamps |
4 | Powertrain Control Module |
5 | Transmission |
6 | Heater/Air Conditioning |
7 | Hazard Warning Flashers |
8 | Power Steering |
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 | Daytime Running Lamps |
15 | Exterior/Interior Lamps |
16 | Air Bag System |
17 | Ignition |
18 | Parking Brake |
19 | Accessory Power |
20 | Sidemarker Lamps |
21 | Auxiliary Wiring |
22 | Turn Signal/Backup Lamps |
23 | Not Used |
24 | Hydraulics/Air Brake |
A | Spare |
B | Spare |
Fuse | Usage |
|---|---|
HTD/MIRR | Heated Mirrors |
Blank | Not Used |
Blank | Not Used |
Blank | Not Used |
LT TRN TRLR | Trailer Left Turn Signal |
Blank | Not Used |
BRK | Brake Warning Lamp |
RT PRK | Right-hand Parking Lamps |
RT TRN TRLR | Trailer Right Turn Signal |
RT LOW BEAM | Right Low-Beam |
LT HI BEAM | Left High-Beam |
LT PARK | Left-hand Parking Lamps |
Blank | Not Used |
RT REAR TRN/STOP | Right Rear Turn Signal/Stoplamp |
LT REAR TRN/STOP | Left Rear Turn Signal/Stoplamp |
RADIO | Radio |
Blank | Not Used |
Blank | Not Used |
Blank | Not Used |
PWR WNDW | Power Windows |
Relay | Usage |
|---|---|
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 |
Underhood Fuse Block
When a circuit goes out, the problem could be in either the primary or secondary underhood fuse blocks. These blocks uses blade-type fuses.
Primary Underhood Fuse Block
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.
Be sure to replace fuses with fuses of the same rating. Do not use fuses of higher amperage than those indicated on the fuse block.
Primary Underhood Fuse Block
Relay | Usage |
|---|---|
NOTE 1 | LG4 Powertrain Control Valve, L18/LB7 Fuel Pump, LG5 Heated Fuel |
IGN B | Ignition |
STARTER | Starter |
HORN | Horn |
IGN A | Ignition |
PTO | Power Take-Off |
REVERSE | Reverse |
NEUTRAL START | Neutral Start |
Fuse | Usage |
|---|---|
RR DEFOG | Rear Defog |
ENG 1 | Engine 1 |
ENG 3 | Engine 3 |
PCM-B | Powertrain Control Module |
BLANK | Empty |
ENG 4 | Engine 4 |
ENG 2 | Engine 2 |
HTD FUEL | Heated Fuel |
BLANK | Empty |
BLANK | Empty |
BLANK | Empty |
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/LB7 Fuel, LG4 Powertrain Control Valve, LG5 Electronic Control Module |
BLANK | Empty |
STUD A | Spare |
STUD B | Spare |
Secondary Underhood Fuse Block
Fuse | 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 | Comfort Control System |
NOTE | C4/C5 Electric Brake, C6/C7/C8 Brake Lamps |
