2003 CHEVROLET ASTRO CARGO VAN trailer

6. Start the engine and let it run until you can feel the
upper radiator hose getting hot. Watch out for the
engine cooling fan.
7. By this time, the coolant level inside the radiator
®ller neck may be lower. If the level is lower, add
more of the proper DEX-COOL
žcoolant mixture
through the ®ller neck until the level reaches
the base of the ®ller neck.
Then replace the pressure cap. At any time during
this procedure if coolant begins to ¯ow out of
the ®ller neck, reinstall the pressure cap. Be sure
the arrow on the pressure cap lines up.
Engine Fan Noise
This vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions, the clutch is not fully engaged. This improves
fuel economy and reduces fan noise. Under heavy
vehicle loading, trailer towing and/or high outside
temperatures, the fan speed increases when the clutch
engages. So you may hear an increase in fan noise.
This is normal and should not be mistaken as the
transmission slipping or making extra shifts. It is merely
the cooling system functioning properly. The fan will
slow down when additional cooling is not required and
the clutch disengages.
You may also hear this fan noise when you start the
engine. It will go away as the fan clutch disengages.
5-39

Fuse/Circuit
BreakerUsage
1Stop/Turn/Hazard Lamps, Center
High Mounted Stop Lamp, Anti-Lock
Brakes
2Radio Accy, Rear Seat Audio
ControlsFuse/Circuit
BreakerUsage
3Courtesy Lamps, Glove Box Lamp,
Dome Reading Lamps, Vanity Mirror
Lamps, Courtesy Lamps
4Daytime Running Lamps Relay,
Instrument Panel Cluster
5 Rear Defogger
6Cruise Module, Truck Body Control
Module, Instrument Panel Cluster,
Cruise Control Switch,
Electrochromic Mirror
7Power Outlets, DLC, Subwoofer
Ampli®er
8Crank Circuit Fuse, Park/Neutral
Switch, Starter Enabler Relay
9License Plate Lamp, Tailamps,
Parking Lamps, Ashtray Lamp,
Panel Lights, Trailer Taillamps, Front
and Rear Sidemarker Lamps, Door
Switch Illumination, Headlamp
Switch Illumination, Rear Seat Audio
Illumination, Truck Body
Control Module
5-94

Fuse/Circuit
BreakerUsage
10 Air Bag System
11 Not Used
12L, M1, M2 Blower Motor, Rear Air
Conditioning Relay Coil, Front Cont.
Temp. Door Motor, HI Blower Relay,
Defogger Timer Coil
13Cigarette Lighter, Door Lock
Switches, Dutch Door Release
Module
14Cluster Illum, Climate Controls,
Chime Module, Radio Illumination,
Rear Heat Switch Illumination, Rear
Wiper/Washer Switch Illumination,
Rear Liftgate Switch Illumination,
Remote Cassette Illumination,
Overhead Console, Truck Body
Control Illumination
15Truck Body Module, Headlamp
Relay
16Front Turn Signals, Rear Turn
Signals, Trailer Turn Signals,
Back-Up Lamps, Brake
Transmission Shift Interlock SolenoidFuse/Circuit
BreakerUsage
17 Front Wipers, Front Washer Pump
18VCM-Ign 3, VCM-Brake, Cruise
Stepper Motor Signal, ATC Module
19Instrument Panel Radio: ATC (Main
Feed), 2000 Series (Standby)
20PRNDL/Odometer, TCC Enable and
PWM Solenoid, Shift A and Shift B
Solenoids, 3±2 Downshift Solenoid,
Instrument Panel Cluster, VCM
Module
21 Powr Adjust Mirrors
22 Not Used
23 Rear Wiper, Rear Washer Pump
24 Not Used
A(Circuit Breaker) Power Door Lock
Relay, 6±Way Power Seats
B (Circuit Breaker) Power Windows
5-95

Relays Usage
A/C Relay
(Rear Heat and
A/C)Rear/Heat and Air Conditioning
Up®tter-ACCY
RelayUp®tter Accessory
Starter Enable
RelayStarter
A/C Enable
RelayAir Conditioning
Headlamps
RelayHeadlamps
Fuel Pump
RelayFuel Pump
Fuse/Circuit
BreakerUsage
UPFITTER-BATTUp®tter Battery Power Stud, Trailer
Wiring Harness
UPFITTER-ACCY Up®tter Accessory Relay
Spare Not used
Spare Not used
Spare Not usedFuse/Circuit
BreakerUsage
ECM-1BFuel Pump Relay and Motor, VCM,
Oil Pressure Switch/Sender
HORN Horn Relay and Horn
A/C COMPAir Conditioning Enable Relay and
Compressor
RR HTR/AC Rear Heater and Air Conditioning
ATC Active Transfer Case-L Van
FRT HVAC Front Heater and Air Conditioning
ENG-IOxygen Sensors, Camshaft Position
Sensor, Mass Air Flow Sensor,
Evaporative Emission Canister Vent
Solenoid
IGN-E Air Conditioning Enable Relay Coil
ECM-IFuel Injectors 1±6, Crankshaft
Position Sensot, VCM, Coil Driver
Module (EST), Ignition Coil
Blank Not Used
RH HDLMP Right Headlamp
LH Headlamp Left Headlamp
Blank Not Used
Blank Not Used
5-97

Selecting the Right Schedule
First you'll need to decide which of the two schedules is
right for your vehicle. Here's how to decide which
schedule to follow:
Short Trip/City De®nition
Follow the Short Trip/City Scheduled Maintenance if any
one of these conditions is true for your vehicle:
·Most trips are less than 5 miles (8 km). This is
particularly important when outside temperatures
are below freezing.
·Most trips include extensive idling (such as frequent
driving in stop-and-go traffic).
·You frequently tow a trailer or use a carrier on top
of your vehicle.
·If the vehicle is used for delivery service, police,
taxi or other commercial application.
One of the reasons you should follow this schedule if
you operate your vehicle under any of these conditions
is that these conditions cause engine oil to break
down sooner.
Short Trip/City Intervals
Every 3,000 Miles (5 000 km):Engine Oil and Filter
Change (or 3 months, whichever occurs ®rst). Chassis
Lubrication (or 3 months, whichever occurs ®rst).
Drive Axle Fluid Check.
Every 6,000 Miles (10 000 km):Tire Rotation.
Every 15,000 Miles (25 000 km):Engine Air Cleaner
Filter Inspection. Front Wheel Bearing Repack
(two±wheel drive only) (or at each brake relining,
whichever occurs ®rst). Automatic Transmission Service
(severe conditions only).
Every 30,000 Miles (50 000 km):Engine Air Cleaner
Filter Replacement. Fuel Filter Replacement.
Every 50,000 Miles (83 000 km):Automatic
Transmission Service (normal conditions). Transfer
Case Fluid Change.
Every 100,000 Miles (166 000 km):Spark Plug Wire
Inspection. Spark Plug Replacement. Positive
Crankcase Ventilation (PCV) Valve Inspection.
Every 150 000 Miles (240 000 km):Cooling System
Service (or every 60 months, whichever occurs
®rst). Engine Accessory Drive Belt Inspection.
These intervals only summarize maintenance services.
Be sure to follow the complete scheduled maintenance
on the following pages.
6-5

Long Trip/Highway De®nition
Follow this scheduled maintenanceonlyif none of the
conditions from the Short Trip/City Scheduled
Maintenance are true. Do not use this schedule if the
vehicle is used for trailer towing, driven in a dusty area
or used off paved roads. Use the Short Trip/City
schedule for these conditions
Driving a vehicle with a fully warmed engine under
highway conditions will cause engine oil to break down
slower.
Long Trip/Highway Intervals
Every 7,500 Miles (12 500 km):Engine Oil and Filter
Change (or every 12 months, whichever occurs ®rst).
Chassis Lubrication (or 12 months, whichever occurs
®rst). Drive Axle Fluid Check. Tire Rotation.
Every 15,000 Miles (25 000 km):Engine Air Cleaner
Filter Inspection. Automatic Transmission Service
(severe conditions only).Every 30,000 Miles (50 000 km):Fuel Filter
Replacement. Engine Air Cleaner Filter Replacement.
Front Wheel Bearing Repack (two±wheel drive only)
(or at each brake relining, whichever occurs ®rst).
Every 50,000 Miles (83 000 km):Automatic
Transmission Service (normal conditions). Transfer
Case Fluid Change.
Every 100,000 Miles (166 000 km):Spark Plug Wire
Inspection. Spark Plug Replacement. Positive
Crankcase Ventilation (PCV) Valve Inspection.
Every 150,000 Miles (240 000 km):Cooling System
Service (or every 60 months, whichever occurs
®rst). Engine Accessory Drive Belt Inspection.
These intervals only summarize maintenance services.
Be sure to follow the complete scheduled maintenance
on the following pages.
6-6

12,000 Miles (20 000 km)
qChange engine oil and ®lter (or every 3 months,
whichever occurs ®rst).An Emission Control Service.
qLubricate chassis components (or every 3 months,
whichever occurs ®rst).(See footnote #.)
qCheck rear/front axle ¯uid level and add ¯uid as
needed. Check constant velocity joints and axle seals
for leaking.
qRotate tires. See
Tire Inspection and Rotation on
page 5-64for proper rotation pattern and additional
information.(See footnote +.)
15,000 Miles (25 000 km)
qChange engine oil and ®lter (or every 3 months,
whichever occurs ®rst).An Emission Control Service.
qLubricate chassis components (or every 3 months,
whichever occurs ®rst).(See footnote #.)
qInspect engine air cleaner ®lter. If necessary, replace
the ®lter. If vehicle is driven in dusty/dirty conditions,
inspect ®lter at every engine oil change. See
Engine
Air Cleaner/Filter on page 5-24for more information.An Emission Control Service. (See footnote ².)
qCheck rear/front axle ¯uid level and add ¯uid as
needed. Check constant velocity joints and axle seals
for leaking.qFor Two-Wheel-Drive vehicles only: Clean and repack
the front wheel bearings (or at each brake relining,
whichever occurs ®rst).
qChange automatic transmission ¯uid and ®lter if the
vehicle is mainly driven under one or more of these
conditions:
þ In heavy city traffic where the outside
temperature regularly reaches 90ÉF (32ÉC)
or higher.
þ In hilly or mountainous terrain.
þ When doing frequent trailer towing.
þ Uses such as found in taxi, police or delivery
service.
If you do not use your vehicle under any of these
conditions, change the ¯uid and ®lter every 50,000 miles
(83 000 km).
18,000 Miles (30 000 km)
qChange engine oil and ®lter (or every 3 months,
whichever occurs ®rst).An Emission Control Service.
qLubricate chassis components (or every 3 months,
whichever occurs ®rst).(See footnote #.)
qCheck rear/front axle ¯uid level and add ¯uid as
needed. Check constant velocity joints and axle seals
for leaking.
qRotate tires. See
Tire Inspection and Rotation on
page 5-64for proper rotation pattern and additional
information.(See footnote +.)
6-8

qChange automatic transmission ¯uid and ®lter if the
vehicle is mainly driven under one or more of these
conditions:
þ In heavy city traffic where the outside
temperature regularly reaches 90ÉF (32ÉC) or
higher.
þ In hilly or mountainous terrain.
þ When doing frequent trailer towing.
þ Uses such as found in taxi, police or delivery
service.
If you do not use your vehicle under any of these
conditions, change the ¯uid and ®lter every 50,000 miles
(83 000 km).
qRotate tires. SeeTire Inspection and Rotation on
page 5-64for proper rotation pattern and additional
information.(See footnote +.)
33,000 Miles (55 000 km)
qChange engine oil and ®lter (or every 3 months,
whichever occurs ®rst).An Emission Control Service.
qLubricate chassis components (or every 3 months,
whichever occurs ®rst).(See footnote #.)
qCheck rear/front axle ¯uid level and add ¯uid as
needed. Check constant velocity joints and axle seals
for leaking.
36,000 Miles (60 000 km)
qChange engine oil and ®lter (or every 3 months,
whichever occurs ®rst).An Emission Control Service.
qLubricate chassis components (or every 3 months,
whichever occurs ®rst).(See footnote #.)
qRotate tires. SeeTire Inspection and Rotation on
page 5-64for proper rotation pattern and additional
information.(See footnote +.)
qCheck rear/front axle ¯uid level and add ¯uid as
needed. Check constant velocity joints and axle seals
for leaking.
39,000 Miles (65 000 km)
qChange engine oil and ®lter (or every 3 months,
whichever occurs ®rst).An Emission Control Service.
qLubricate chassis components (or every 3 months,
whichever occurs ®rst).(See footnote #.)
qCheck rear/front axle ¯uid level and add ¯uid as
needed. Check constant velocity joints and axle seals
for leaking.
6-10