Chevrolet 2007 TrailBlazer Owner's Manua page 124

Shifting Into Four-Wheel Low
To shift to Four-Wheel Low, the vehicle's engine
must be running and the vehicle must be stopped
or moving less than 2 mph (3.2 km/h) with the
transmission in NEUTRAL (N). The preferred
method for shifting into Four-Wheel Low is to have
your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h).
Turn the knob to Four-Wheel Low. You must
wait for the Four-Wheel Low indicator light to stop
flashing and stay on before shifting the
transmission into gear.
If you turn the knob to Four-Wheel Low when your
vehicle is in gear and/or moving, the Four-Wheel
Low indicator light will flash for 30 seconds and not
complete the shift unless your vehicle is moving
less than 2 mph (3.2 km/h) and the transmission is
in NEUTRAL (N). After 30 seconds, the transfer
case will return to the setting last chosen.
124
Shifting Out of Four-Wheel Low
To shift from Four-Wheel Low to Four-Wheel High,
Auto Four-Wheel Drive, or Two-Wheel High,
your vehicle must be stopped or moving less than
2 mph (3.2 km/h) with the transmission in
NEUTRAL (N) and the engine running. The
preferred method for shifting out of Four-Wheel
Low is to have your vehicle moving 1 or 2 mph
(1.6 to 3.2 km/h). Turn the knob to Four-Wheel
High, Auto Four-Wheel Drive, or Two-Wheel High.
You must wait for the Four-Wheel High, Auto
Four-Wheel Drive, or Two-Wheel High indicator
light to stop flashing and stay off before shifting
your transmission into gear.
If the knob is turned to Four Wheel-High, Auto
Four-Wheel Drive, or Two-Wheel High when your
vehicle is in gear and/or moving, the Four-Wheel
High, Auto Four-Wheel Drive, or Two-Wheel
High indicator light will flash for 30 seconds. It will
not complete the shift unless your vehicle is
moving less than 2 mph (3.2 km/h) with the
transmission in NEUTRAL (N).