GMC Duramax Diesel 2015 Owner's Manual page 56

Caution
Water in the diesel fuel can
corrode internal components of
the fuel system and lead to
severe damage. It can also
support fungus or bacteria
growth, which can damage the
fuel system and fuel operated
heater (FOH) (if equipped). Even
with a diesel fuel biocide, the fuel
system may still need to be
cleaned. Your dealer can advise
of the appropriate solution.
If the fuel tank needs to be
purged to remove water, see your
dealer or a qualified technician.
Improper purging can damage the
fuel system and block the FOH.
Water in Fuel Troubleshooting
If the WATER IN FUEL SERVICE
REQUIRED message comes on:
Recommended
Problem
Message The fuel filter is
displays but approximately
goes off during half full of water.
the ignition Drain the water
cycle. immediately.
See "Removing
Water from Fuel
Filter" later in
this section.
Driving and Operating
Problem
Message
displays and
Action
stays on.
9-29
Recommended
Action
Drain the fuel
filter
immediately.
If no water can
be drained, and
the temperature
is below
freezing, then
water may be
frozen in the
filter. Move the
vehicle to a
warm location to
thaw, then drain
the fuel. If still
no water drains,
see your dealer.