GMC 2003 C4C042 Owner's Manual page 352

15,000 Miles (24 000 km)
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Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See "Engine Oil" in the Index. (3)(9)
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Chassis lubrication service (or every 6 months,
whichever occurs first). (12)
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Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)
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DURAMAX Diesel Only: Replace fuel filter.
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Steering system service. (13)
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Front and rear suspension service. (14)
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- - -
Spring to axle U bolts and shackle bolts
service. (16)
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Exhaust system service (or every 6 months,
whichever occurs first). (3)(4)(17)
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Wheels and tires service. (15)
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Hydraulic brake service (or every 6 months,
whichever occurs first). (7)(46)
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Parking brake service (or every 6 months, whichever
occurs first). (8)
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Thermostatically controlled engine cooling fan
service. (4)(20)
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Shields and underhood insulation service. (4)(5)(21)
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L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
7-6
20,000 Miles (32 000 km)
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DURAMAX Diesel Only: Change engine oil
and filter (or every 12 months, whichever occurs
first). (2)(3)
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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)
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Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See "Engine Oil" in the Index. (3)(9)
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Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)
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Chassis lubrication service (or every 6 months,
whichever occurs first). (12)
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Inspect door hinge pins and bushings and replace
as necessary.
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Cooling system service. Clean the cooling system
filler 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.