GMC TopKick 2007 Owner's Manual page 253

If the light comes on, use this chart to determine
what action to take.
Water In Fuel Light
Problem
Light comes on
intermittently.
Light stays on at
temperatures above
freezing.
Light stays on at
temperatures below
freezing.
Light stays on
immediately after
refueling, and a large
amount of water was
possibly pumped into the
fuel tank.
Recommended Action
Drain water from
the fuel filter.
Drain the fuel filter
immediately. If no water
can be drained and the
light stays on, see your
dealer for assistance.
Drain the fuel filter
immediately. If no water
can be drained, water
may be frozen in the
water drain system, or in
the fuel lines. Move the
vehicle to a warm location
to thaw out, and then
drain the filter system.
Fuel tank purging is
required. See your dealer
for assistance.
Notice: If you drive when this warning
indicator is on, you can damage your fuel
injection system and your engine. If the
indicator comes on right after you refuel, it
means water was pumped into your fuel tank.
Turn off your engine immediately. Then,
have the water drained at once.
To drain water, do the following:
1. Stop and park the vehicle in a safe place.
Turn off the engine and apply the parking
brake.
2. Remove the fuel cap.
3. Place a fuel-resistant container under the fuel
filter. The filter drain valve is located on the
bottom of the fuel filter.
If your vehicle has the 6.6L engine, the fuel filter
is located in the engine compartment on the
driver's side of the vehicle. If your vehicle has
either the 7.2L or 7.8L engine, the fuel filters
are located in the engine compartment on the
driver's side of the vehicle, and on the driver's
side frame rail in front of the fuel tank.
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