Engine Checks Before Operating - GMC 2010 T-Series Owner's Manual

Exhaust Restrictor
If the vehicle is equipped with this feature, there is an
exhaust restrictor valve located in the exhaust stream.
The valve closes to provide back pressure to the engine
for the purpose of warming the engine quickly.
The exhaust restrictor operates:
while the engine is running.
while the vehicle is not moving.
while the accelerator, brake and clutch pedals are
not pressed on a manual transmission vehicle.
while idling in cold temperatures.
when the shifter is in N (Neutral) or P (Park) on an
automatic transmission vehicle.
On vehicles equipped with a diesel engine exhaust
brake, the exhaust brake switch must be on. See Diesel
Engine Exhaust Brake on page 2 16 for more
information. The indicator in the exhaust brake switch
will be lit when the exhaust restrictor is active. The
exhaust brake indicator light in the center of the
instrument panel will also be lit whenever the exhaust
restrictor is active. See Exhaust Brake Indicator Light
on page 3 35 for more information.
When the engine coolant temperature is below
149°F (65°C) and the outside temperature is below
50°F (10°C), the exhaust restrictor will come on within
60 seconds of starting the engine. After running the
engine for an additional 10 seconds, the engine idle
will increase.
The exhaust restrictor will shut off and engine idle will
return to normal once the engine is warmed up, or the
brake pedal is pressed.

Engine Checks Before Operating

When you have started the engine, let it run for
20 to 30 seconds before you put a load on it. But do
not leave the vehicle while the engine is running.
Avoid unnecessary idling of diesel engine equipped
vehicles.
If the engine idles too long, the temperature of the
engine coolant will fall below the normal operating
range. Low engine operating temperature causes
several conditions which affect engine operation and
reduce engine life.
The engine should be permitted to go through a
warm-up period. Operate the vehicle at a minimum of
600 rpm during the warm-up period. During this period
and during operation, the following observations should
be made.
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