
Device Usage
DEFOG Rear Defogger Relay
HDLNR 1 Headliner Wiring Connector 1
SPARE RELAY Not Used
CB SEATDriver and Passenger Seat
Module Circuit Breaker
CB RT DOORRight Power Windows Circuit
Breaker
SPARE Not Used
INFOInfotainment Harness
ConnectionUnderhood Fuse Block
The underhood fuse block in the engine compartment
on the driver’s side of the vehicle near the battery.
Lift the cover for access to the fuse/relay block.
To remove fuses hold the end of the fuse between your
thumb and index nger and pull straight out.
SeeEngine Compartment Overview on page 5-14for
more information on its location.
5-125

*1— Gasoline Engine and Diesel Engine.
*2— Gasoline Engine; ECMRPV — Diesel Engine.
*3— Gasoline Engine; FUEL HT — Diesel Engine.
*4— Gasoline Engine; ECM I — Diesel Engine.
*5— IGN/EDU
Fuses Usage
GLOW PLUGDiesel Glow Plugs and Intake
Air Heater
CUST FEED Gasoline Accessory Power
HYBRID Hybrid
STUD #1Auxiliary Power (Single
Battery and Diesels Only)/
Dual Battery (TP2) Do not
install fuse.
MBECMid Bussed Electrical Center
Power Feed, Front Seats,
Right Doors
BLOWER Front Climate Control Fan
LBECLeft Bussed Electrical Center,
Door Modules, Door Locks,
Auxiliary Power Outlet—Rear
Cargo Area and Instrument
Panel
STUD 2Accessory Power/Trailer
Wiring Brake Feed
Fuses Usage
ABS Anti-Lock Brakes
VSES/ECAS Vehicle Stability
IGN A Ignition Power
IGN B Ignition Power
LBEC 1Left Bussed Electrical Center,
Left Doors, Truck Body
Controller, Flasher Module
TRL PARK Parking Lamps Trailer Wiring
RR PARKRight Rear Parking and
Sidemarker Lamps
LR PARKLeft Rear Parking and
Sidemarker Lamps
PARK LP Parking Lamps Relay
STRTR Starter Relay
INTPARK Interior Lamps
STOP LP Stoplamps
TBC BATTTruck Body Controller Battery
Feed
S/ROOF Sunroof
SEO B2 Off-Road Lamps
4WSVent Solenoid
Canister/Quadrasteer Module
Power
RR HVAC Not Used
5-127

Fuses Usage
AUX PWRAuxiliary Power
Outlet — Console
IGN 1 Ignition Relay
PCM 1 Powertrain Control Module
ETC/ECMElectronic Throttle Control,
Electronic Brake Controller
IGN EInstrument Panel Cluster, Air
Conditioning Relay, Turn
Signal/Hazard Switch, Starter
Relay
RTD Ride Control
TRL B/U Backup Lamps Trailer Wiring
PCM BPowertrain Control Module,
Fuel Pump
F/PMP Fuel Pump (Relay)
B/U LPBack-up Lamps, Automatic
Transmission Shift Lock
Control System
RR DEFOG Rear Window Defogger
HDLP-HI Headlamp High Beam Relay
PRIME Not Used
02B Oxygen Sensors
AIRBAGSupplemental In atable
Restraint System
FRT PARKFront Parking Lamps,
Sidemarker LampsFuses Usage
DRLDaytime Running Lamps
(Relay)
SEO IGN Rear Defog Relay
TBC IGN1 Truck Body Controller Ignition
HI HDLP-LT High Beam Headlamp-Left
LH HID Not Used
DRL Daytime Running Lamps
RVC Regulated Voltage Control
IPC/DICInstrument Panel
Cluster/Driver Information
Center
HVAC/ECAS Climate Control Controller
CIG LTR Cigarette Lighter
HI HDLP-RT High Beam Headlamp-Right
HDLP-LOW Headlamp Low Beam Relay
A/C COMP Air Conditioning Compressor
A/C COMPAir Conditioning Compressor
Relay
RR WPR Not Used
RADIO Audio System
SEO B1Mid Bussed Electrical Center,
Rear Heated Seats,
HomeLink
LO HDLP-LT Headlamp Low Beam-Left
5-128

Fuses Usage
BTSIBrake Transmission Shift
Interlock System
CRNK Starting System
LO HDLP-RT Headlamp Low Beam-Right
FOG LP Fog Lamp Relay
FOG LP Fog Lamps
HORN Horn Relay
W/S WASHWindshield Washer Pump
Relay
W/S WASH Windshield Washer Pump
INFOOnStar
®/Rear Seat
Entertainment
RADIO AMP Radio Ampli er
RH HID Not Used
HORN Horn
EAP Not Used
TREC All-Wheel Drive Module
SBA Supplemental Brake Assist
Auxiliary Electric Cooling Fan
Fuse Block
The auxiliary electric
cooling fan fuse block is
located in the engine
compartment on the
driver’s side of the vehicle
next to the underhood
fuse block.
Lift the cover for access to the fuse/relay block.
Fuses Usage
COOL/FAN Cooling Fan
COOL/FAN Cooling Fan Relay Fuse
COOL/FAN Cooling Fan Fuse
Relays Usage
COOL/FAN 1 Cooling Fan Relay 1
COOL/FAN 3 Cooling Fan Relay 3
COOL/FAN 2 Cooling Fan Relay 2
5-129

(b)Visually inspect front and rear suspension and
steering system for damaged, loose or missing parts,
signs of wear or lack of lubrication. Inspect power
steering lines and hoses for proper hook-up, binding,
leaks, cracks, cha ng, etc. Visually check constant
velocity joints, rubber boots and axle seals for leaks.
(c)Visually inspect hoses and have them replaced if they
are cracked, swollen or deteriorated. Inspect all pipes,
ttings and clamps; replace with genuine GM parts as
needed. To help ensure proper operation, a pressure test
of the cooling system and pressure cap and cleaning the
outside of the radiator and air conditioning condenser is
recommended at least once a year.
(d)Visually inspect wiper blades for wear or cracking.
Replace blade inserts that appear worn or damaged
or that streak or miss areas of the windshield.
(e)Make sure the safety belt reminder light and all your
belts, buckles, latch plates, retractors and anchorages
are working properly. Look for any other loose or
damaged safety belt system parts. If you see anything
that might keep a safety belt system from doing its
job, have it repaired. Have any torn or frayed safety belts
replaced. Also look for any opened or broken airbag
coverings, and have them repaired or replaced.
(The airbag system does not need regular maintenance.)(f)Lubricate all key lock cylinders, body door hinges,
hood latch assembly, secondary latch, pivots, spring
anchor, release pawl, tailgate hinges, tailgate linkage,
tailgate handle pivot points, latch bolt, fuel door
hinge, locks and folding seat hardware. More frequent
lubrication may be required when exposed to a corrosive
environment. Applying silicone grease on weatherstrips
with a clean cloth will make them last longer, seal
better and not stick or squeak.
(g)Check vent hose at transfer case for kinks and
proper installation.
(h)Change automatic transmission uid and lter if the
vehicle GVWR is over 8600 lbs or if the vehicle is
mainly driven under one or more of these conditions:
In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
In hilly or mountainous terrain.
When doing frequent trailer towing.
Uses such as found in taxi, police or delivery
service.
(i)Drain, ush and re ll cooling system. This service
can be complex; you should have your dealer perform
this service. See Engine Coolant on page 5-35for
what to use. Inspect hoses. Clean radiator, condenser,
pressure cap and ller neck. Pressure test the cooling
system and pressure cap.
6-9

At Least Once a Year
Starter Switch Check
{CAUTION:
When you are doing this inspection, the
vehicle could move suddenly. If the vehicle
moves, you or others could be injured.
1. Before you start, be sure you have enough room
around the vehicle.
2. Firmly apply both the parking brake and the regular
brake. SeeParking Brake on page 2-48if
necessary.
Do not use the accelerator pedal, and be ready to
turn off the engine immediately if it starts.
3. Try to start the engine in each gear. The starter
should work only in PARK (P) or NEUTRAL (N).
If the starter works in any other position, contact
your GM Goodwrench
®dealer for service.
Automatic Transmission Shift Lock
Control System Check
{CAUTION:
When you are doing this inspection, the
vehicle could move suddenly. If the vehicle
moves, you or others could be injured.
1. Before you start, be sure you have enough room
around the vehicle. It should be parked on a level
surface.
2. Firmly apply the parking brake. SeeParking Brake
on page 2-48if necessary.
Be ready to apply the regular brake immediately if
the vehicle begins to move.
3. With the engine off, turn the ignition to RUN, but do
not start the engine. Without applying the regular
brake, try to move the shift lever out of PARK (P)
with normal effort. If the shift lever moves out
of PARK (P), contact your GM Goodwrench
®dealer
for service.
6-12

Ignition Transmission Lock Check
While parked, and with the parking brake set, try to turn
the ignition to LOCK in each shift lever position.
The ignition should turn to LOCK only when the
shift lever is in PARK (P).
The key should come out only in LOCK.
Contact your GM Goodwrench
®dealer if service is
required.
Parking Brake and Automatic
Transmission Park (P) Mechanism Check
{CAUTION:
When you are doing this check, your vehicle
could begin to move. You or others could be
injured and property could be damaged. Make
sure there is room in front of your vehicle in
case it begins to roll. Be ready to apply the
regular brake at once should the vehicle begin
to move.Park on a fairly steep hill, with the vehicle facing
downhill. Keeping your foot on the regular brake, set the
parking brake.
To check the parking brake’s holding ability: With
the engine running and transmission in
NEUTRAL (N), slowly remove foot pressure from
the regular brake pedal. Do this until the vehicle is
held by the parking brake only.
To check the PARK (P) mechanism’s holding ability:
With the engine running, shift to PARK (P). Then
release the parking brake followed by the regular
brake.
Contact your GM Goodwrench
®dealer if service is
required.
Underbody Flushing Service
At least every spring, use plain water to ush any
corrosive materials from the underbody. Take care to
clean thoroughly any areas where mud and other debris
can collect.
6-13