2003 GMC ENVOY trailer

If No Steam Is Coming From Your
Engine
If you get an engine overheat warning but see or hear
no steam, the problem may not be too serious.
Sometimes the engine can get a little too hot when you:
·Climb a long hill on a hot day.
·Stop after high-speed driving.
·Idle for long periods in traffic.
·Tow a trailer.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. In heavy traffic, let the engine idle in neutral while
stopped. If it is safe to do so, pull off the road,
shift to PARK (P) or NEUTRAL (N) and let
the engine idle.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning doesn't come back on, you can drive
normally.
If the warning continues and you have not stopped, pull
over, stop, and park your vehicle right away.
If there's still no sign of steam, you can push down the
accelerator until the engine speed is about twice as
fast as normal idle speed for at least three minutes while
you're parked. If you still have the warning,
turn off
the engine and get everyone out of the vehicleuntil it
cools down.
You may decide not to lift the hood but to get service
help right away.
5-28

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.
8. 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 pressure cap is hand-tight.
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 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.
5-35

Fuses Usage
1Electrically-Controlled Air
Suspension
2Passenger's Side High-Beam
Headlamp
3Passenger's Side Low-Beam
Headlamp
4 Back-Up-Trailer Lamps
5 Driver's Side High-Beam Headlamp
6 Driver's Side Low-Beam Headlamp
7 Wash
8 Automatic Transfer Case
9 Windshield Wipers
10 Powertrain Control Module B
11 Fog Lamps
12 Stop Lamp
13 Cigarette Lighter
14 Ignition Coils
15 Air Suspension Ride
16 TBD-Ignition 1Fuses Usage
17 Crank
18 Air Bag
19 Electric Brake
20 Cooling Fan
21 Horn
22 Ignition E
23 Electronic Throttle Control
24Instrument Panel Cluster, Driver
Information Center
25 Automatic Shift Lock Control System
26 Engine 1
27 Back-Up
28 Powertrain Control Module 1
29 Oxygen Sensor
30 Air Conditioning
31 Truck Body Controller
32 Trailer
33 Anti-Lock Brakes (ABS)
5-93

Fuses Usage
34 Ignition A
35 Blower Motor
36 Ignition B
50 Passenger's Side Trailer Turn
51 Driver's Side Trailer Turn
52 Hazard Flashers
Relays Usage
37 Blank
38 Rear Window Washer
39 Fog Lamps
40 HornFuses Usage
41 Fuel Pump
42 Windshield Wipers/Washer
43 High-Beam Headlamp
44 Air Conditioning
45 Cooling Fan
46 Headlamp Driver Module
47 Starter
Miscellaneous Usage
48 Instrument Panel Battery
49 Blank
5-94

Fuses Usage
1Electrically-Controlled Air
Suspension
2Passenger's Side High-Beam
Headlamp
3Passenger's Side Low-Beam
Headlamp
4 Back-Up-Trailer Lamps
5 Driver's Side High-Beam Headlamp
6 Driver's Side Low-Beam Headlamp
7 Wash
8 Automatic Transfer Case
9 Windshield Wipers
10 Powertrain Control Module B
11 Fog Lamps
12 Stop Lamp
13 Cigarette Lighter
14 Ignition Coils
15 Cannister Vent
16 TBD-Ignition 1
17 Crank
18 Air Bag
19 Electric Brake
20 Cooling Fan
21 HornFuses Usage
22 Ignition E
23 Electronic Throttle Control
24Instrument Panel Cluster, Driver
Information Center
25 Automatic Shift Lock Control System
26 Engine 1
27 Back-Up
28 Powertrain Control Module 1
30 Air Conditioning
31 Truck Body Controller 1
32 Trailer
33 Anti-Lock Brakes (ABS)
34 Ignition A
35 Blower Motor
36 Ignition B
50 Passenger's Side Trailer Turn
51 Driver's Side Trailer Turn
52 Hazard Flashers
53 Oxygen Sensor Bank A
54 Oxygen Sensor Bank B
55 Injector Bank A
56 Injector Bank B
Relays Usage
37 Headlamp Washer
5-96

Fuses Usage
23 Blank
24 Unlock
25 Blank
26 Blank
27 OH Battery/OnStar
žSystem
29 RainsenseŸ Wipers
30 Parking Lamps
31Truck Body Controller 4 Cruise
Control
32 Truck Body Controller 5
33 Front Wipers
34 Vehicle Stop
35 Blank
36 Heat Ventilation Air Conditioning B
37 Front Parking Lamps
38 Left Turn Signal
Fuses Usage
39 Heat Ventilation Air Conditioning 1
40 Truck Body Controller 4
41 Radio
42 Trailer Park
43 Right Turn Signal
44 Heat Ventilation Air Conditioning
45 Rear Fog Lamps
46 Auxiliary Power 1
47 Ignition 0
48 Four-Wheel Drive
49 Blank
50 Truck Body Controller Ignition
51 Brakes
52 Truck Body Controller Run
5-99

Fuses Usage
22 Retained Accessory Power
23 Blank
24 Unlock
25 Blank
26 Blank
27 OH Battery/OnStar
žSystem
28 Sunroof
29 RainsenseŸ Wipers
30 Parking Lamps
31Truck Body Controller 4 Cruise
Control
32 Truck Body Controller 5
33 Front Wipers
34 Vehicle Stop
35 Blank
36 Heat Ventilation Air Conditioning B
37 Front Parking Lamps
Fuses Usage
38 Left Turn Signal
39 Heat Ventilation Air Conditioning 1
40 Truck Body Controller 4
41 Radio
42 Trailer Park
43 Right Turn Signal
44 Heat Ventilation Air Conditioning
45 Rear Fog Lamps
46 Auxiliary Power 1
47 Ignition 0
48 Four-Wheel Drive
49 Blank
50 Truck Body Controller Ignition
51 Brakes
52 Truck Body Controller Run
5-101

50,000 Miles (83 000 km)
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 at 100,000 miles
(166 000 km).
qAutomatic Transfer Case Only: Change transfer case
¯uid.
52,500 Miles (87 500 km)
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 5-55for proper rotation pattern and additional
information.(See footnote +.)
60,000 Miles (100 000 km)
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 5-55for proper rotation pattern and additional
information.(See footnote +.)
qReplace fuel ®lter.An Emission Control Service. (See
footnote ².)
qReplace engine air cleaner ®lter on vehicles without
a restriction indicator. If equipped with a change
indicator, inspect the indicator. If necessary, replace
the ®lter. If vehicle is driven in dusty/dirty conditions,
inspect the change indicator (if equipped) at every
engine oil change. See
Engine Air Cleaner/Filter on
page 5-20for more information.An Emission
Control Service. (See footnote ².)
67,500 Miles (112 500 km)
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 5-55for proper rotation pattern and additional
information.(See footnote +.)
6-8