Fuse Usage
RH PARK LP Right-hand Parking Lamps
LH PARK LP Left-hand Parking Lamps
RADIO U Radio
PWR WINDOW Power Windows
BRAKE ISO Brake Warning Lamp
SPARE Spare Fuse
L-RR TRUCK Left Rear Trailer Wiring
SPARE Spare Fuse
SPARE Spare Fuse
SPARE Spare Fuse
R-RR TRUCK Right Rear Trailer Wiring
SPARE Spare Fuse
Relay Usage
BRAKE LAMPC4/C5 Brake Lamps,
C6/C7/C8 Tractor/Trailer Wiring
IGN 4 IgnitionRelay Usage
MARKER LP Sidemarker and Clearance Lamps
HTD FUEL LB7/LG4 Heated Fuel
AIR HTR LG4 Air Heater
ECU MAINTAIN LG4 Electronic Control Unit
DRL Daytime Running Lamps
CHMSL ISO Center High Mounted Stop Lamp
HTD MIRR Heated Mirrors
R-TRN TLR Right Trailer Turn Signal
L-TRN TLR Left Trailer Turn Signal
SPARE Spare Relay
SPARE Spare Relay
SPARE Spare Relay
5-89
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.
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.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 Primary Underhood
Fuse Block
Primary Underhood Fuse Block
5-91
Relay Usage
PTO Power Take-Off
REVERSE Reverse
NEUTRAL
STARTNeutral 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 EmptyFuse Usage
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 2L18/LB7 Fuel, LG4 Powertrain
Control Valve, LG5 Electronic
Control Module
BLANK Empty
STUD A Spare
STUD B Spare
5-92
Scheduled Maintenance
The services shown in this schedule up to 100,000 miles
(166 000 km) should be repeated after 100,000 miles
(166 000 km) at the same intervals for the life of
this vehicle. The services shown after 100,000 miles
(166 000 km) should be repeated at the same miles (km)
after those intervals for the life of this vehicle.
Gasoline engine vehicles have a computer that lets you
know when to change your engine oil. This is not
based on mileage, but on engine revolutions and engine
operating temperature. When the computer has
calculated that the oil needs changing, the GM Oil Life
System will indicate that a change is necessary.
The “Footnotes” at the end of this Maintenance
Schedule further explain maintenance services.
SeeService Publications Ordering Information on
page 7-7.
100 Miles (160 km)
❑Wheel stud nut service.(46)
1,000 Miles (1 600 km)
❑Wheel stud nut service.(46)
❑Rear axle air shift motor service.(11)
7,500 Miles (12 000 km)
❑Gasoline Engine Only: Check Oil Life System. If
engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the Index.(3) (9)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (6)
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(12)
❑Wheels and tires service.(15)
❑Hydraulic brake service (or every 6 months, whichever
occurs first).(7) (46)
❑Parking brake service (or every 6 months, whichever
occurs first).(8)
❑Air brake service (or every 6 months, whichever
occurs first).(39)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(40)
❑Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
❑Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(41)
❑Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever occurs
first).(42)
6-5
10,000 Miles (16 000 km)
❑DURAMAX™ Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first).(2) (3)
15,000 Miles (24 000 km)
❑Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the
Index.(3) (9)
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(12)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (6)
❑Gasoline Engine: Inspect engine air cleaner filter if
you are driving in dusty conditions and replace
filter if necessary. Diesel Engine: Inspect engine air
cleaner filter change indicator. If necessary,
replace the filter. If vehicle is driven in dusty/dirty
conditions, inspect filter change indicator at
every engine oil change. SeeEngine Air
Cleaner/Filter on page 5-30for more
information.† (3)
❑DURAMAX™ Diesel Only: Replace fuel filter.
❑Steering system service.(13)
❑Front and rear suspension service.(14)
❑Spring-to-axle U-bolts and shackle bolts service.(16)❑Exhaust system service (or every 6 months,
whichever occurs first).(3) (4) (17)
❑Wheels and tires service.(15)
❑Hydraulic brake service (or every 6 months,
whichever occurs first).(7) (46)
❑Parking brake service (or every 6 months, whichever
occurs first).(8)
❑Air brake service (or every 6 months, whichever
occurs first).(39)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(40)
❑Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
❑Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(41)
❑Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever occurs
first).(42)
❑Thermostatically controlled engine cooling fan
service.(4) (20)
❑Shields and underhood insulation service.(4) (5) (21)
6-6
20,000 Miles (32 000 km)
❑DURAMAX™ Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first).(2) (3)
❑Air compressor dry element pleated paper air strainer
service (or every 2 months or every 800 hours,
whichever occurs first).
22,500 Miles (36 000 km)
❑Gasoline Engine Only: Check Oil Life System. If
engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the Index.(3) (9)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (6)
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(12)
❑Inspect door hinge pins and bushings and replace as
necessary.
❑Cooling system service. Clean the cooling system filter
cap with clean water, clean the core, pressure test the
cap and the system for proper pressure capability and
inspect condition of cooling and heater hoses and
clamps. Replace hoses if cracked, swollen or
damaged.
❑Wheel bearing (grease type) service (or every
24 months, whichever occurs first, and whenever hubs
are removed).(23) (46)❑Wheels and tires service.(15)
❑Hydraulic brake service (or every 6 months, whichever
occurs first).(7) (46)
❑Parking brake service (or every 6 months, whichever
occurs first).(8)
❑Air brake service (or every 6 months, whichever
occurs first).(39)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(40)
❑Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
❑Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(41)
❑Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever occurs
first).(42)
❑Air intake system service (or every 24 months,
whichever occurs first).(4) (5) (24)
❑Evaporative Control System service (if equipped) (or
every 24 months, whichever occurs first).(3) (26) †
❑Rear axle air shift motor service.(11)
6-7
30,000 Miles (48 000 km)
❑Gasoline Engine Only: Check Oil Life System. If
engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the Index.(3) (9)
❑DURAMAX™ Diesel Only: Change engine oil and filter
(or every 12 months, whichever occurs first).(2) (3)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (6)
❑Gasoline Engine: Replace engine air cleaner filter.
Diesel Engine: Inspect engine air cleaner filter change
indicator. If necessary, replace the filter. If vehicle is
driven in dusty/dirty conditions, inspect filter change
indicator at every engine oil change. SeeEngine Air
Cleaner/Filter on page 5-30for more information.† (3)
❑DURAMAX™ Diesel Only: Replace fuel filter.
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(12)
❑Replace fuel filter(s) (or every 12 months, whichever
occurs first).(3)
❑Steering system service.(13)
❑Front and rear suspension service.(14)
❑Spring-to-axle U-bolts and shackle bolts service.(16)
❑Exhaust system service (or every 6 months, whichever
occurs first).(3) (4) (17)
❑Wheels and tires service.(15)❑Hydraulic brake service (or every 6 months, whichever
occurs first).(7) (46)
❑Parking brake service (or every 6 months, whichever
occurs first).(8)
❑Air brake service (or every 6 months, whichever
occurs first).(39)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(40)
❑Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
❑Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(41)
❑Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever occurs
first).(42)
❑C600, C700 and C800 Gasoline Engines Only: Engine
drive belts service (or every 12 months, whichever
occurs first.)(18)
❑Thermostatically controlled engine cooling fan
service.(4) (20)
❑Shields and underhood insulation service.(4) (5) (21)
6-8
37,500 Miles (60 000 km)
❑Gasoline Engine Only: Check Oil Life System. If
engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the Index.(3) (9)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (6)
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(12)
❑Wheels and tires service.(15)
❑Hydraulic brake service (or every 6 months, whichever
occurs first).(7) (46)
❑Parking brake service (or every 6 months, whichever
occurs first).(8)
❑Air brake service (or every 6 months, whichever
occurs first).(39)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(40)❑Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
❑Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(41)
❑Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever occurs
first).(42)
40,000 Miles (64 000 km)
❑DURAMAX™ Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first).(2) (3)
❑Air compressor dry element pleated paper air strainer
service (or every 2 months or every 800 hours,
whichever occurs first).
6-9