Page 229 of 374

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
228 Driving and Operating
When Operating the PTO
For operation of special equipment,
see the manufacturer’s instructions.
Installations, or alterations to the
original equipment vehicle or
chassis, as manufactured and
assembled by General Motors, are
not covered by this warranty. The
body company, assembler,
or equipment installer is solely
responsible for warranties on the
body or equipment and any
alterations to any of the parts,
components, systems,
or assemblies installed by GM.
Examples include, but are not
limited to, special body installation,
such as recreational vehicles, the
installation of any non-GM part,
cutting, welding, or the
disconnecting of original equipment
vehicle or chassis parts and
components, extension of the
wheelbase, suspension, and
driveline modifications, and axle
additions.
The engine control module (ECM)
has the ability to accommodate one
of three different PTO modes. Each mode can be programmed to
accommodate many PTO devices.
Optional PTO switches are available
from your dealer to ease installation
of a PTO.
The optional PTO main switch and
PTO engine speed control switch
can be used increase the engine
idle r/min without additional
programming. Pressing the PTO
main switch once will activate the
PTO mode and raise the idle up
speed up to the preset 800 r/min.
Once in PTO mode the PTO engine
speed control switch can be used to
adjust the idle speeds between the
preset 1,300 and 1,700 r/min.
Moving the selector lever from park
or neutral, applying the brake pedal
or releasing the parking brake will
cancel PTO mode and return the
engine idle speed to normal. For
additional details about PTO
programming, contact your dealer.
Page 232 of 374

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
Vehicle Care 231
Vehicle Checks
Doing Your Own
Service Work
Precautions for Checking and
Adjustments
Your authorized dealer has trained
technicians and genuine parts to
service your vehicle properly. For
expert advice and quality service,
see your authorized dealer.
{Warning
To help avoid personal injury, take
care when doing any
maintenance or making any
check or repair. Follow
manufacturer's instructions for all
materials used during service and
maintenance of this vehicle.
If used or handled improperly,
they may be hazardous. Improper
or incomplete service can also
affect the vehicle and result in(Continued)
Warning (Continued)
personal injury, or damage to the
vehicle or its equipment. If you
have any questions about
carrying out some service, have
the work done by a skilled
technician.
To prevent personal injury, keep
hands, tools and clothing clear of
the engine cooling fan when the
engine is running.
The engine, exhaust pipe and
radiator will be hot immediately
after the vehicle is driven. Be
careful around these parts to
prevent burns. Perform all checks
when the engine is cold.
Do not perform work near an
open flame or other heat sources.
Do not let the engine run in poorly
ventilated garages or sheds. This
could cause carbon monoxide
poisoning.(Continued)
Warning (Continued)
Performing maintenance work on
a truck or chassis can be
dangerous. In trying to do some
jobs, you can be seriously injured.
Do your own maintenance work
only if you have the required
know-how and the proper tools
and equipment for the job. If you
have any doubts, contact your
dealer.
You and others could be seriously
injured.
Pull firmly on the parking brake
lever and move the selector lever to
"P" and make sure the shift indicator
displays "P".
Make sure to turn off the engine and
remove the key from the engine
control switch before performing any
checks.
Select a place with a solid and level
surface to perform the checking and
maintenance work. Make sure to
Page 234 of 374
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
Vehicle Care 233
Cab Tilting
Before Tilting the Cab (Single Cab
Model)
{Warning
To help avoid personal injury and
property damage:. Park the vehicle on level
ground and check that there
is enough space in front of
and above the cab.
. Set the parking brake firmly
and block the front wheels.
. Move the selector lever in
the "P" position.
. Secure loose articles in
the cab.
. Stop the engine.
. Close the cab door.
. Keep the area surrounding
the cab clear.
You and others could be seriously
injured. Tilting the Cab
1. Check that all personnel are clear of the cab.
2. Unlock the handle (2) whilepulling the lever (1).
3. Hold the assist handle (3) andpull the safety hook (4).
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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
242 Vehicle Care
For the crew cab vehicle, the
dipstick is located beneath the
rear-of-engine inspection panel.
After unlatching the A/T fluid
inspection cover, the dipstick will be
visible.
Inspection
Wait at least 30 minutes before
checking the transmission fluid if
you have been driving at high speed
for a long period of time, in city/
heavy traffic or while pulling a trailer.1. Start the engine, and drive the vehicle for approximately
10 minutes to warm up the
engine. During 10 minutes, the automatic transmission fluid
should reach a temperature of
approximately 70 - 80 °C (158 -
176 °F). During the winter
when temperatures are low,
adjust the amount of driving
time according to the actual
conditions.
2. Park the vehicle on level ground, and firmly apply the
parking brake.
3. With the engine idling, move the selector lever from the “P”
position to the “1”position
while pressing the brake pedal,
and then return the lever from
the “1”position to the “P”
position.
4. With the engine still idling, pull out the dipstick and wipe it with
a clean cloth.Transmission Dipstick
5. Reinsert the dipstick into position, pull out the dipstick
slowly, and check whether the
fluid level is within the “H”
marked range. Always check
the fluid level at least twice.
Consistently is important in
maintaining accuracy.
If inconsistent readings persist,
check the transmission
breather to ensure that it is
clean and free of debris.
. Dipstick C (COLD) —
Transmission fluid
temperature Approx. 20 -
30 °C (68 - 86 °F).
Page 265 of 374

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
264 Vehicle Care
Automatic Transmission
Shift Lock Control
Function Check
When the Selector Lever
Cannot be Moved From the "P"
Position
Perform the following when the
selector lever cannot be moved from
the "P" position.
Caution
When the selector cannot be
operated from the P position to
any other position even after
performing the operation below
repeatedly, the shift lock system
may have a failure. Have the
vehicle inspected at your dealer.
When performing the below
operations, make sure the parking
brake is securely engaged. 1. Securely pull the parking brake lever and stop the engine.
2. Remove the cup holder (1) byremoving the three Torx®
bolts (2).
3. Remove the selector levercover by removing the four
screws and lifting it up.
4. Operate the selector lever (1)
while pressing the release
lever (2).
When installing the cover, perform
the removal procedure in reverse
order.
Page 279 of 374

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
278 Vehicle Care
The Location of Fuses and Relays
The fuses (3) and relays (2) are
located in the lower part of the
instrument panel in the center and
in the left rear of the cab.
The cover (1) must be opened in
order to carry out inspection and
replacement. In addition, the
cover (1) of the relay box at the left
rear of the cab must also be opened
at this time.
If you should spill water or a
beverage on the cover, wipe it off
before opening the cover.
The area around the cover may get
warm when the vehicle is being
driven, but this is not abnormal.Replacing Fuses
1. Before replacing fuses, firmly apply the parking brake, move
the selector lever to the
P (Park) position, and turn the
engine control switch to the
LOCK position.
2. The fuse puller is stored in the fuse box inside the cab. Place
the fuse puller on the fuse and
pull it out.
3. If the fuse appears asshown (2), the fuse is blown.
Replace with a spare fuse (1).
Spare fuses are stored in the
fuse box inside the cab.
Page 283 of 374
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
282 Vehicle Care
Relay LocationRelay locations:
No. Description
1 STOP LAMP
2 DAYTIME RUNNING LAMP
3 KEY ON
4 PARKING/NEUTRAL
5 –
6 WIPER MAIN
7 HORN
8 WIPER HI LO
9 TRAILER BRAKE
10 POWER WINDOW
11 BACK UP LAMP
12 POWER WINDOW
13 HEAD LAMP LO
14 VACUUM PUMP
15 HEAD LAMP HI
16 TAIL LAMP
17 CIGAR LIGHTER
18 CORNERING LAMP
Page 304 of 374

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
Vehicle Care 303
the negative (–) terminal which
is grounded (attached to the
engine block, or frame rail).
2. Position the vehicle with the good (charged) battery so that
the booster (jumper) cables will
reach. But never let the
vehicles touch. Also, be sure
the booster cables to be used
do not have loose or missing
insulation.
3. In both vehicles, turn off the ignition (engine control) switch
and all lights and accessories
except the hazard flasher or
any lights needed for the work
area. In both vehicles, apply
the parking brake firmly and
move the selector lever to the
"P" position.
4. Unlatch the latches (1) and
remove the battery cover (2)
and connect the jumper cables
in the numbered sequence in
the drawing below. Make sure
the cable clamps do not touch
any other metal parts. Make sure the cables are not
on or near pulleys, fans or
other parts that will move when
the engine is started.
When it is difficult to start the
engine in a cold area, first start
the engine of the vehicle with
the booster battery or batteries
and a few minutes after that
start the engine of the disabled
vehicle.