Page 216 of 388

Engine Fan Noise
Your 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 fan
is spinning slower and 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 as the
clutch more fully 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 partially disengages.
You may
also hear this fan noise when you start the engine.
It will go away as the fan clutch partially disengages.
If a Tire Goes Flat
It’s unusual for a tire to “blow out” while you’re driving,
especially if you maintain your tires properly.
If air goes
out of a tire, it’s much more likely
to leak out slowly.
But
if you should ever have a “blowout,” here are a
few tips about what to expect and what to do:
If a front tire fails, the flat tire will create a drag that
pulls the vehicle toward that side. Take your foot off the
accelerator pedal and grip the steering wheel firmly.
Steer to maintain lane position, and then gently brake to
a stop
well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like
a skid and may require the same correction you’d use
in a skid. In any rear blowout, remove your foot from
the accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop
-- well off the road if possible.
If a tire goes flat, the next part shows how to use your
jacking equipment to change a flat tire safely.
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Page 246 of 388

Among those acts presumed to constitute tampering are
the acts listed below.
Insulation:
Removal of the noise shields or underhood insulation.
Engine:
Removal or rendering engine speed governor (if
equipped) inoperative
so as to allow engine speed to
exceed manufacturer specifications.
Fan and Drive:
Removal of fan clutch (if equipped) or rendering
clutch inoperative.
Removal of the fan snroud (if equipped).
Air Intake:
Removal of the air cleaner silencer.
Reversing the air cleaner cover.
Exhaust:
Removal of the muffler and/or resonator.
Removal of the exhaust pipes and exhaust pipe clamps.
Engine Oil (Gasoline Engine)
If your vehicle has a diesel engine, see “Engine Oil
(Diesel Engine)” in the Diesel Engine Supplement.
It’s a good idea to check your engine oil every time you
get fuel. In order to get an accurate reading, the oil must
be warm and the vehicle must be on level ground.
Turn
off the engine and give
the oil a few minutes to
drain back into the oil
pan. If you don’t, the oil
dipstick might not show
the actual level.
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Page 297 of 388
Engine Compartment Fuse Relay Center
The fuse block is on the driver's side of the engine
compartment at the rear.
[-I
[)
[T]
Name
BLOWER
ABS
Circuits Protected
Blower Motor
Electronic Brake Control Module
Name
IGN-B
IGN-A
BATT
LIGHTING
RR BLOWER
ENG-
1
A/C SPARE
AUX A
AUX-B
RH-HDLP
Circuits Protected
Ignition Switch
Starter Relay, Ignition Switch
Instrument Panel Fuse Block
Instrument Panel Fuse Block,
Headlamp Switch
Rear Auxiliary Blower
Motor Relays
Heated
02 Sensors, Mass Air
Flow Sensor, EGR Valve
Solenoid, Evap Canister Purge
Valve, Crankshaft Position Sensor,
Secondary Air Injection Relay
(Diesel), Water in Fuel Sensor
(Diesel), Fuel Heater (Diesel),
Glowplug Relay (Diesel),
Wastegate Solenoid (Diesel)
Air Conditioning Clutch Relay
Spare Fuses
Upfitter Provisions
Upfitter Provisions
Right-hand Headlamp
(Export Only)
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Page 298 of 388

Name
RH-HIBM
ECM-I
HORN
LH-HDLP
LH-HIBM
FUEL SOL
IGN-E
ECM-B
Circuits Protected
Right-hand High-beam Headlamp
(Export Only)
Ignition Coil, Crankshaft Position Sensor, VCM, Fuel Injectors,
Coil Driver
Horn Relay, Underhood Lamp(
s)
Left-hand Headlamp
(Export Only)
Left-hand High-beam Headlamp
(Export Only)
PCM, Fuel Solenoid Driver,
Engine Shutoff Solenoid
Air Conditioning Clutch Relay
Fuel Pump Relay, VCM, PCM,
Fuel Pump and Engine Oil
Pressure Switch
Capacities and Specifications
Replacement Parts
Replacement part numbers listed in this section are
based on the latest information available at the time of
printing, and are subject to change. If a part listed in this
manual is not the same as the part used in your vehicle
when
it was built, or if you have any questions, please
contact your GM truck dealer.
These specifications
are for information only. If you
have
any questions, see the service manual for the
chassis or refer to the body manufacturer’s publications.
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