engine CHEVROLET LOW CAB FORWARD 2020 Repair Manual

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
60 Instruments and Controls
Engine Coolant
Temperature Gauge
With the engine control switch in the
ON position, this gauge indicates
the temperature of the engine
coolant.“C”means cold while “H”
means hot. During operation, the
needle should stay in the safety
zone. See Engine Overheating
0 249.
{Warning
If the engine coolant temperature
gauge shows an overheat
condition or you have any other
reason to suspect the engine may
be overheating, continued
operation of the engine, even for
a short time, may result in a fire
and the risk of personal injury and
severe vehicle damage. Take
immediate action as outlined in
Engine Overheating. See Engine
Overheating 0249.
Caution
If the needle goes up above the
upper limit and enters the H zone,
the engine is likely to overheat.
Immediately pull safely off the
road out of the way of traffic and
take the necessary actions to
deal with engine overheating.
If the needle nears the H zone but
(Continued)
Caution (Continued)
does not cross into it, this is not a
problem, but check the engine
coolant level in the reservoir. Add
engine coolant as necessary.
See “Engine Overheat Warning
Light” under Driver Information
Center (DIC) 070 and
Engine Coolant 0243.
Diesel Exhaust Fluid
(DEF) Gauge
The DEF gauge is part of the Driver
Information Center (DIC). See
Driver Information Center (DIC)
070.
Seat Belt Reminders
Seat Belt Warning Light
There is a driver seat belt reminder
light on the instrument cluster.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
Instruments and Controls 61
This warning light comes on and a
warning buzzer sounds when the
driver is not wearing the seat belt
while the engine control switch is in
the ON position.
When the vehicle speed exceeds
20 km/h (12 mph) with the seat belt
unbuckled, the warning light will
flash and the buzzer will continue to
sound. The warning light will go out
and the warning buzzer will stop
when the driver buckles the
seat belt.
Battery Warning Light
This 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 (such as a loose or broken
fan belt). Pull off to a safe place well
clear of traffic and contact your
dealer. Driving while this light is on
could drain the battery.
Check and Corrective Action1. Check to see if the fan belt is broken or loose.
2. If the fan belt is loose, adjust the tension.
3. If the fan belt is broken or there is no abnormality in the fan
belt, see your dealer for
service.
See Battery - North America 0259,
Jump Starting - North America
0 301, and Engine Drive Belt
Routing 0355.Malfunction Indicator
Lamp (Check Engine
Light)
This light should come on to show
that it is working when the engine
control switch is turned to the ON
position, and then should go out
after the engine is started.
If this light stays on or comes on
while the engine is running, it
indicates a malfunction with the
engine electronic emission control
system. Avoid driving at high
speeds and have the vehicle
inspected by your dealer.
If this light comes on when the fuel
tank is empty, you do not need to
have your vehicle serviced. See
Running Out of Fuel 0224.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
62 Instruments and Controls
If this light comes on intermittently
or continuously while driving,
service is required. Even if the
vehicle is drivable and does not
require towing, see your dealer as
soon as possible. Continued driving
without having the system serviced
could cause damage to the
emission control system. It could
also affect fuel economy and
drivability.
Service Vehicle Soon
Light
This light comes on briefly when the
engine control switch is in the ON
position, 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, the vehicle control
system may be malfunctioning. Take
the vehicle to your dealer for service
as soon as possible.
Brake System Warning
Light (Parking Brake
Light)
This light should come on briefly
when the engine control switch is
turned to the ON position, and then
should go out after the engine is
started.
Brake System Warning Light
If the light remains on after engine
start up or comes on during
operation of the vehicle, it means
that there is something wrong with
part of the brake system.The brake system warning light
comes on while the engine is
running (after startup) in the
following situations:
.
Drop in the level of brake fluid
(due to brake lining wear or fluid
leakage).
. Abnormality in the charging
system (such as an alternator
malfunction or loose or split
fan belt).
. Abnormality in the anti-lock
brake system (ABS) and
Electronic Braking force
Distribution (EBD) functions.
(The ABS warning light and
brake system warning light will
illuminate at the same time.) See
Antilock Brake System (ABS)
Warning Light 064.
To serve as a reminder, the light
should stay on when the parking
brake is not fully released, and the
engine control switch is on. Have
the system repaired if the light does
not come on when it should. If this

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
Instruments and Controls 63
warning light does not go away,
brake inspection and maintenance
should be performed.
Check and Corrective Action
1. Check to see that the parkingbrake has been fully released.
If it has, check the following:
2. Turn on the exhaust brake to help slow the vehicle.
3. Pull off the road and stop carefully. Remember that
stopping distances may be
longer, the pedal may be
harder to push, and the pedal
may go down farther than
normal.
4. Check the brake fluid reservoir on the left side of the
instrument panel. If low, add
fluid as needed.
5. If the brake fluid is not low: Try out the brakes by starting and
stopping on the shoulder of the
road, then either drive
cautiously at a safe speed to
the nearest dealer for repair,
if you judge driving to be safe; or have the vehicle towed to
the nearest dealer for repair.
Continued driving without the
necessary repairs could be
dangerous.
If this warning light stays on, see
your dealer.
The regular braking system is a split
system designed so that one part
will provide some braking if there is
a loss of hydraulic pressure in the
other part of the system.
{Warning
If this warning light comes on
while the engine is running,
immediately stop the vehicle at a
safe place well clear of traffic and
contact your dealer for inspection.
When the brake system warning
light is illuminated, brake
effectiveness may be decreased.
When this happens, strongly
press the brake pedal.
See Brakes 0253.
Parking Brake Light
This indicator light comes on when
the parking brake lever is pulled
with the engine control switch on.
This light also stays on when the
parking brake is not fully released
and the engine control switch is on.
If this warning light stays on, see
your dealer.
The illumination of the parking brake
light does not necessarily ensure
firm application of the parking brake.
The parking brake lever must be
sufficiently pulled up and locked.
Be careful not to drive the vehicle
with the parking brake lever still
pulled up.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
64 Instruments and Controls
Brake Low Vacuum Warning
Light
This light should come on briefly
when the engine control switch is
turned to the ON position, and then
should go out after the engine is
started. If the light does not come
on when the engine control switch is
turned to ON, it could indicate a
burned out bulb or a blown fuse.
Have the system repaired if the light
does not come on during this check.
The warning light and buzzer will
come on simultaneously when the
brake booster’s vacuum or pressure
becomes insufficient either during
driving or when the engine control
switch is in the ON position, or when
there is an abnormality in the
charging system, such as an
alternator malfunction or loosening
or splitting of the fan belt or whenever the hydraulic brake
booster (HBB) becomes faulty. The
warning buzzer will stop sounding
when the parking brake is engaged.
On 4500HD and 4500XD, the brake
low vacuum warning light and
warning buzzer should come on to
indicate low vacuum reserve for
brake power assist. At the same
time, the Back up Electric Vacuum
Pump operates.
(5500HD, 5500XD models) When
the HBB pressure is low, and/or the
HBB fluid (Dexron
–VI) level is low,
the light and warning buzzer should
come on. Do not use brake fluid in
the brake booster reservoir. Use
only Dexron –VI ATF.
If this happens while driving:
. Do not pump the brakes. The
system is designed to stop the
truck with reserve power assist if
the pedal is held down. This
reserve is greatly reduced each
time you apply and release the
brakes.
. Stopping distance may be
longer. .
You may have to push much
harder on the brake pedal.
. Have the vehicle repaired before
you continue driving.
The buzzer stops when the selector
lever is shifted to the P position.
{Warning
Do not drive while the buzzer
sounds as the brakes are not
operating to their full capacity.
You and others could be seriously
injured.
Antilock Brake System
(ABS) Warning Light
This light comes on briefly when the
engine control switch is turned to
the ON position, and then should go

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
Instruments and Controls 65
out after approximately
three seconds. If the light does not
come on, have it fixed so it will be
ready to warn if there is a problem.
If this warning light stays on more
than three seconds or comes on
while driving, there is a problem in
the Anti-lock Brake System (ABS).
In this case, the ABS stops working
but the brakes still function as
ordinary service brakes.
{Warning
If this warning light comes on
while driving, immediately stop
your vehicle at a safe place well
clear of traffic and take the
following actions.1. Stop the engine.
2. Restart the engine. Check ifthe ABS warning light
comes on and then goes
out. If it does, there is no
problem. The ABS operates
normally.
(Continued)
Warning (Continued)
3. Move the vehicle slowlyforward. Gradually increase
the speed to 15 km/h
(9 mph). If the light goes off,
the ABS is normal.
If the light does not come on or
go out, or comes on frequently,
contact your dealer immediately
and have the system repaired.
Even if a problem has occurred in
the ABS, the brakes will still work
as normal brakes. In this case,
the ABS has no influence on the
operation of the brake system.
See Brake System Warning Light
(Parking Brake Light) 062 and
Antilock Brake System (ABS) 0207.
Exhaust Brake Light
This light comes on when the
exhaust switch is pulled and the
engine is running. See Exhaust
Brake 0213.
Service Transmission
Warning Light
This light comes on briefly when the
engine control switch is in the ON
position, as a check to show the
light is working. It should go out
when the engine is started.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
66 Instruments and Controls
If this light comes on while driving, it
indicates that there is a malfunction
in the automatic transmission’s
electronic control system. If the
warning light is on, see your dealer
for service.
Automatic Transmission
Fluid Temperature
Warning Light
This light comes on briefly when the
engine control switch is in the ON
position as a check to show the light
is working. It should go out when
the engine is started.
The Automatic Transmission Fluid
(ATF) Temperature warning light
comes on if the ATF temperature is
high. This usually occurs when the
transmission is overfilled and maybe accompanied by leakage of fluid
from the transmission
breather hose.
If the light stays on, or comes on
while driving, slow down and pull off
the road. Stop the vehicle at a safe
place and put the vehicle in
P (Park). With the engine idling, wait
until the light goes off. If the light
goes off, you can drive the vehicle
again. Continuing to drive while this
light is on may damage the
transmission. While this light is on,
the transmission cannot operate in
all gears. If you attempt to shift
gears, the vehicle may not continue
to move. If you cannot drive to a
dealer immediately, have the vehicle
towed.
Caution
Driving with the ATF warning light
constantly on can cause serious
mechanical damage to the
automatic transmission.
See Automatic Transmission 0196.
Overdrive Off Light
This light should come on briefly
when the engine control switch is
turned on as a check to make sure
the light is working. It should go out
automatically.
This light comes on when the
overdrive off switch on the selector
lever is turned on. Overdrive will not
operate even when the automatic
transmission is in D, unless engine
speed is excessive.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
Instruments and Controls 67
Wait-to-Start Light
This light comes on when the
engine control switch is turned to
the ON position and goes out when
preheating is complete.
SeeStarting and Stopping the
Vehicle 0159.
Engine Oil Pressure Light
This light should come on briefly
when the engine control switch is
turned to the ON position, and then
should go out after the engine is
started. This light comes on when the
engine oil pressure has fallen below
the normal level while the engine is
running or the oil pressure across
the oil filter rises above the normal
level while the engine is running.
If the warning light comes on while
driving, immediately pull off to a
safe place and stop the engine.
Check the oil level in the engine
crankcase. If the oil level is normal,
restrictions are in the oil filter or
within the lubricating system. Have
the vehicle inspected at your dealer.
Do not run the engine with this light
on. It could damage the engine.
When this light comes on while
driving, a warning tone also sounds.
The oil level varies while the engine
is running right after it has stopped
or if the vehicle is on uneven
ground. As a result, the red engine
oil pressure warning light may
light up.
When checking the oil level, press
the engine oil level check switch on
level ground while the engine is
cool. The red engine oil pressurewarning light in combination with the
green engine oil level indicator light
can indicate if the engine oil level is
OK or low.
While driving, this light will also
activate the engine alarm and
automatic shutdown system.
See
Engine Oil Level Indicator Light
0 67 and
Engine Oil 0235.
Engine Oil Level Indicator
Light
When the engine oil level check
switch is pushed with the engine
control switch in LOCK, the green
engine oil level indicator light will
come on if the engine oil level
is OK.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
68 Instruments and Controls
SeeEngine Oil Pressure Light 067
and
Engine Oil 0235.
Diesel Exhaust Fluid
(DEF) Warning Light
This light should come on briefly
when the engine control switch is
turned to the ON position, and go off
when the engine has started.
This light comes on as a warning
related to the selective catalytic
reduction (SCR) system. If this light
comes on, check the DEF gauge.
Add DEF if necessary. If DEF level
is OK, have your vehicle serviced
by your dealer.
Also see Diesel Exhaust Fluid
0 180.
Engine Shutdown
Warning Light
The Engine Shutdown Warning light
comes on briefly when the engine
control switch is turned to the ON
position, as a check to show the
light is working. The light turns off
when the engine is started.
This light will come on when the
engine alarm and automatic
shutdown system is active. See
Engine Alarm and Automatic
Shutdown 0164.
Idle Shutdown Light
This light comes on briefly when the
engine control switch is in the ON
position and then should go out
when the engine has started.
Idle stop is a dealer programmable
function which will automatically turn
off the engine, at idle, when specific
programmed conditions are met.
See your dealer for details.
This light comes on as an alert that
programmed conditions have been
met and the engine is about to shut
down. This light stays on after the
engine has stopped. See Idle
Shutdown 0164.

Chevrolet Low Cab Forward 5.2L Diesel Engine 4500 HD/XD/5500 HD/XD
Owner Manual (GMNA-Localizing-U.S.-13337621) - 2020 - crc - 12/5/18
Instruments and Controls 69
Reduced Engine Power
Light
This light comes on briefly when the
engine control switch is turned to
the ON position, and then should go
out after the engine is started.
If this light comes on while the
engine is running, it indicates power
is being reduced due to one or more
of the following conditions:
.Malfunction of the engine or
exhaust electronic control
system.
. DEF level is too low or empty.
If this light comes on with the
malfunction indicator lamp, see your
dealer immediately. If this light comes on with the Refill
Diesel Exhaust Fluid (DEF) warning
light and the DEF warning light, refill
DEF as soon as possible.
See
“Refill Diesel Exhaust Fluid
(DEF) Warning Light” underDriver
Information Center (DIC) 070. See
Malfunction Indicator Lamp (Check
Engine Light) 061 and
Diesel Exhaust Fluid (DEF) Warning
Light 068.
High-Beam On Light
This light comes on when the
high-beam headlamps are in use or
the headlamps are cycled between
high and low beams (passing
signal).
See Headlamp High/Low-Beam
Changer 081.
Daytime Running Lamps
(DRL) Indicator Light
This light comes on when the DRL
are on. If the vehicle is started
during the daytime with the lighting
switch off and the parking brake
released, the low beam headlamps
will come on at a reduced
brightness. The light will go out
when the lighting switch is
turned on.
See Exterior Lamp Controls 080.