2020 GMC SIERRA service

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
126 Instruments and Controls
2. Redistributions in binary formmust reproduce the above
copyright notice, this list of
conditions and the following
disclaimer in the
documentation and/or other
materials provided with the
distribution.
3. Neither the name of the copyright holder nor the names
of its contributors may be used
to endorse or promote products
derived from this software
without specific prior written
permission.
THIS SOFTWARE IS PROVIDED
BY THE COPYRIGHT HOLDERS
AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT
NOT LIMITED TO, THE IMPLIED
WARRANTIES OF
MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT
SHALL THE COPYRIGHT HOLDER
OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF
SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA,
OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY
OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF
THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.Warning Lights,
Gauges, and
Indicators
Warning lights and gauges can
signal that something is wrong
before it becomes serious enough
to cause an expensive repair or
replacement. Paying attention to the
warning lights and gauges could
prevent injury.
Some warning lights come on briefly
when the engine is started to
indicate they are working. When
one of the warning lights comes on
and stays on while driving, or when
one of the gauges shows there may
be a problem, check the section that
explains what to do. Waiting to do
repairs can be costly and even
dangerous.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 133
Uplevel English Fuel Gauge
Shown, Base Level and Midlevel Fuel Gauge Similar
When the ignition is on, the fuel
gauge indicates about how much
fuel is left in the tank.
There is an arrow near the fuel
gauge pointing to the side of the
vehicle the fuel door is on.
When the indicator nears empty, the
low fuel light comes on. There still is
a little fuel left, but the vehicle
should be refueled soon.
Here are four things that some
owners ask about. None of these
show a problem with the fuel gauge: .
At the service station, the fuel
pump shuts off before the gauge
reads full.
. It takes a little more or less fuel
to fill up than the gauge
indicated. For example, the
gauge may have indicated the
tank was half full, but it actually
took a little more or less than
half the tank's capacity to fill
the tank.
. The gauge moves a little while
turning a corner or speeding up.
. The gauge takes a few seconds
to stabilize after the ignition is
turned on, and goes back to
empty when the ignition is
turned off.
Engine Oil Pressure
Gauge
Uplevel Metric Shown, Base Level
and Midlevel Similar

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
134 Instruments and Controls
Uplevel English Shown, BaseLevel and Midlevel Similar
The engine oil pressure gauge
shows the engine oil pressure
in kPa (kilopascals) or psi (pounds
per square inch) when the engine is
running.
Oil pressure can vary with engine
speed, outside temperature, coolant
temperature, and oil viscosity.
On some models, the oil pump will
vary engine oil pressure according
to engine needs. Oil pressure may
change quickly as the engine speed
or load varies. This is normal. If the
oil pressure warning light or Driver Information Center (DIC) message
indicates oil pressure outside the
normal operating range, check the
vehicle's oil as soon as possible.
See
Engine Oil 0339.
Caution
Lack of proper engine oil
maintenance can damage the
engine. Driving with the engine oil
low can also damage the engine.
The repairs would not be covered
by the vehicle warranty. Check
the oil level as soon as possible.
Add oil if required, but if the oil
level is within the operating range
and the oil pressure is still low,
have the vehicle serviced. Always
follow the maintenance schedule
for changing engine oil.
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
Engine Coolant
Temperature Gauge
Uplevel Metric Shown, Base Level and Midlevel Similar

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 135
Uplevel English Shown, BaseLevel and Midlevel Similar
This gauge measures the
temperature of the vehicle's engine
coolant.
While driving under normal
operating conditions, if the needle
moves into the red warning area,
the engine is too hot. Pull off the
road, stop the vehicle, and turn off
the engine as soon as possible.
Voltmeter Gauge
Uplevel Shown, Base Level and Midlevel Similar
When the ignition is on, this gauge
indicates the battery voltage.
When the engine is running, this
gauge shows the condition of the
charging system. The gauge can
transition from a higher to lower or a
lower to higher reading. This is
normal. If the vehicle is operating
outside the normal operating range,
the charging system light comes on.
See Charging System Light 0138. The voltmeter gauge may also read
lower when in fuel economy mode.
This is normal.
Readings outside the normal
operating range can also occur
when a large number of electrical
accessories are operating in the
vehicle and the engine is left idling
for an extended period. This
condition is normal since the
charging system is not able to
provide full power at engine idle. As
engine speeds are increased, this
condition should correct itself as
higher engine speeds allow the
charging system to create maximum
power.
The vehicle can only be driven for a
short time with the readings outside
the normal operating range. If the
vehicle must be driven, turn off all
accessories, such as the radio and
air conditioner.
Readings outside the normal
operating range indicate a possible
problem in the electrical system.
Have the vehicle serviced as soon
as possible.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 137
The airbag readiness light comes on
for several seconds when the
vehicle is started. If the light does
not come on then, have it fixed
immediately.
{Warning
If the airbag readiness light stays
on after the vehicle is started or
comes on while driving, it means
the airbag system might not be
working properly. The airbags in
the vehicle might not inflate in a
crash, or they could even inflate
without a crash. To help avoid
injury, have the vehicle serviced
right away.
If there is a problem with the airbag
system, a Driver Information Center
(DIC) message may also come on.
Passenger Airbag Status
Indicator
The vehicle has a passenger
sensing system. See Passenger
Sensing System 078 for important safety information. The overhead
console has a passenger airbag
status indicator.
United States
Canada
When the vehicle is started, the
passenger airbag status indicator
will light ON and OFF, or the
symbols for on and off, for several
seconds as a system check. Then,
after several more seconds, the
status indicator will light either ON
or OFF, or either the on or off
symbol, to let you know the status of
the front outboard passenger frontal
airbag. If the word ON or the on symbol is
lit on the passenger airbag status
indicator, it means that the front
outboard passenger frontal airbag is
allowed to inflate.
If the word OFF or the off symbol is
lit on the passenger airbag status
indicator, it means that the
passenger sensing system has
turned off the front outboard
passenger frontal airbag.
If, after several seconds, both status
indicator lights remain on, or if there
are no lights at all, there may be a
problem with the lights or the
passenger sensing system. See
your dealer for service.
{Warning
If the airbag readiness light ever
comes on and stays on, it means
that something may be wrong
with the airbag system. To help
avoid injury to yourself or others,
have the vehicle serviced right
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
138 Instruments and Controls
Warning (Continued)
away. SeeAirbag Readiness
Light 0136 for more information,
including important safety
information.
Charging System Light
The charging system light comes on
briefly when the ignition is turned
on, but the engine is not running, as
a check to show the light is working.
It should go out when the engine is
started.
If the light stays on, or comes on
while driving, there may be a
problem with the electrical charging
system. Have it checked by your
dealer. Driving while this light is on
could drain the battery. When this light comes on, or is
flashing, the Driver Information
Center (DIC) also displays a
message.
If a short distance must be driven
with the light on, be sure to turn off
all accessories, such as the radio
and air conditioner.
Malfunction Indicator
Lamp (Check Engine
Light)
This light is part of the vehicle’s
emission control on-board
diagnostic system. If this light is on
while the engine is running, a
malfunction has been detected and
the vehicle may require service. The
light should come on to show that it
is working when the ignition is on
and the engine is not running. See
Ignition Positions (Keyless Access)
0
208 or
Ignition Positions (Key Access)
0 210.
Malfunctions are often indicated by
the system before any problem is
noticeable. Being aware of the light
and seeking service promptly when
it comes on may prevent damage.
Caution
If the vehicle is driven continually
with this light on, the emission
control system may not work as
well, the fuel economy may be
lower, and the vehicle may not
run smoothly. This could lead to
costly repairs that might not be
covered by the vehicle warranty.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Instruments and Controls 139
Caution
Modifications to the engine,
transmission, exhaust, intake,
or fuel system, or the use of
replacement tires that do not
meet the original tire
specifications, can cause this light
to come on. This could lead to
costly repairs not covered by the
vehicle warranty. This could also
affect the vehicle’s ability to pass
an Emissions Inspection/
Maintenance test. See
Accessories and Modifications
0329.
If the light is flashing : A
malfunction has been detected that
could damage the emission control
system and increase vehicle
emissions. Diagnosis and service
may be required.
To help prevent damage, reduce
vehicle speed and avoid hard
accelerations and uphill grades. If towing a trailer, reduce the
amount of cargo being hauled as
soon as possible.
If the light continues to flash, find a
safe place to park. Turn the vehicle
off and wait at least 10 seconds
before restarting the engine. If the
light is still flashing, follow the
previous guidelines and see your
dealer for service as soon as
possible.
If the light is on steady :
A
malfunction has been detected.
Diagnosis and service may be
required.
Check the following:
. If fuel has been added to the
vehicle using the capless funnel
adapter, make sure that it has
been removed. See “Filling the
Tank with a Portable Gas Can”
under Filling the Tank (Pickup
Model) 0283 or
Filling the Tank (Chassis Cab
Model) 0285. The diagnostic
system can detect if the adapter
has been left installed in the
vehicle, allowing fuel to evaporate into the atmosphere.
A few driving trips with the
adapter removed may turn off
the light.
. Poor fuel quality can cause
inefficient engine operation and
poor driveability, which may go
away once the engine is warmed
up. If this occurs, change the
fuel brand. It may require at
least one full tank of the proper
fuel to turn the light off. See
Recommended Fuel (Except
6.2L V8 Engine) 0280 or
Recommended Fuel (6.2L
V8 Engine) 0281.
If the light remains on, see your
dealer.
Emissions Inspection and
Maintenance Programs
If the vehicle requires an Emissions
Inspection/Maintenance test, the
test equipment will likely connect to
the vehicle's Data Link
Connector (DLC).

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
140 Instruments and Controls
The DLC is under the instrument
panel to the left of the steering
wheel. Connecting devices that are
not used to perform an Emissions
Inspection/Maintenance test or to
service the vehicle may affect
vehicle operation. SeeAdd-On
Electrical Equipment 0322. See
your dealer if assistance is needed.
The vehicle may not pass
inspection if:
. The light is on when the engine
is running.
. The light does not come on
when the ignition is on while the
engine is off.
. Critical emission control systems
have not been completely
diagnosed. If this happens, the
vehicle would not be ready for
inspection and might require
several days of routine driving before the system is ready for
inspection. This can happen if
the 12-volt battery has recently
been replaced or run down, or if
the vehicle has been recently
serviced.
See your dealer if the vehicle will
not pass or cannot be made ready
for the test.
Brake System Warning
Light
MetricEnglish
This light should come on briefly
when the vehicle is turned on. If it
does not come on then, have it fixed
so it will be ready to warn you if
there is a problem.
If the light comes on and stays on at
start up, there is a brake problem.
Have the brake system inspected
right away. If the light comes on while driving,
pull off the road and stop carefully.
If equipped with electric brake
boost, vehicle speed may be limited
when the brake system warning
light comes on. The brake pedal
might be harder to push, or the
brake pedal may go closer to the
floor. It could take longer to stop.
If the light is still on, have the
vehicle towed for service. See
Towing the Vehicle
0424.
{Warning
The brake system might not be
working properly if the brake
system warning light is on.
Driving with the brake system
warning light on can lead to a
crash. If the light is still on after
the vehicle has been pulled off
the road and carefully stopped,
have the vehicle towed for
service.