GMC 2003 C4C042 Owner's Manual page 263

If it comes on, use this chart.
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.
Water In Fuel Indicator Chart
Problem Recommended Action
Indicator comes Drain water from fuel filter.
on intermittently.
Indicator
stays on:
S
At Drain fuel filter immediately.
temperatures If no water can be drained and
above freezing. light stays on, see your dealer
for assistance.
S
At Drain fuel filter immediately. If no
temperatures water can be drained
below freezing. be frozen in water drain system.
Water may be frozen in the fuel
lines. Move the vehicle to a warm
location to thaw out, and then
drain filter system.
S
Immediately Fuel tank purging required. See
after refueling, your dealer for assistance.
large amount of
water possibly
pumped into
fuel tank.
--
water may
6-9