GMC 2014 Sierra Owner's Manual page 451

2. If you have a vehicle with a
diesel engine with two batteries,
you should know before you
begin that, especially in cold
weather, you may not be able to
get enough power from a single
battery in another vehicle to start
your diesel engine. If your
vehicle has more than one
battery, using the battery that is
closer to the starter will reduce
electrical resistance. This is
located on the passenger side,
in the rear of the engine
compartment.
3. Get the vehicles close enough
so the jumper cables can reach,
but be sure the vehicles are not
touching each other. If they are,
it could cause an unwanted
ground connection. You would
not be able to start your vehicle,
and the bad grounding could
damage the electrical systems.
To avoid the possibility of the
vehicles rolling, set the parking
brake firmly on both vehicles
involved in the jump start
procedure. Put the automatic
transmission in P (Park) or a
manual transmission in Neutral
before setting the parking brake.
If you have a four-wheel-drive
vehicle, be sure the transfer
case is in a drive gear, not in
N (Neutral).
If any accessories are left on or
plugged in during the jump
starting procedure, they could be
damaged. The repairs would not
be covered by the vehicle
warranty. Whenever possible, turn
off or unplug all accessories on
either vehicle when jump starting.
4. Turn off the ignition on both
vehicles. Unplug unnecessary
accessories plugged into the
accessory power outlets. Turn
off the radio and all the lamps
that are not needed. This will
avoid sparks and help save both
batteries. And it could save the
radio!
5. Open the hood on the other
vehicle and locate the
positive (+) and negative ( )
terminal locations on that
vehicle.
The positive (+) terminal is under
a red plastic cover at the positive
battery post. To uncover the
positive (+) terminal, open the
red plastic cover.
For more information on the
location of the remote
positive (+) and remote negative
( ) terminals, see
.