2003 GMC Sierra 1500 Pickup Owner's Manual - Page 127

If the 4HI, AUTO 4WD or 2HI switch is pressed when your vehicle is in gear and/or moving, the 4HI, AUTO 4WD or 2HI indicator light will flash for 30 seconds but will not complete the shift unless your vehicle is moving less than 3 mph (4.8 km/h) and the transmission is in NEUTRAL (N). Shifting Out of NEUTRAL To shift out of NEUTRAL: 1. Set the parking brake and apply the regular brake pedal. 2. Shift the transmission to NEUTRAL (N) and turn the ignition to RUN with the engine off. 3. Press the button for the desired transfer case shift Shifting into NEUTRAL To shift the transfer case to NEUTRAL do the following: 1. Make sure the vehicle is parked so that it will not roll. 2. Set the parking brake. 3. Start the vehicle or turn the ignition to RUN. 4. Connect the vehicle to the towing vehicle. 5. Put the transmission in NEUTRAL (N). 6. Shift the transfer case to 2HI. 7. Simultaneously press and hold the 2HI and 4LO buttons for 10 seconds. The red NEUTRAL light will come on when the transfer case shift to NEUTRAL is complete. 8. Shift the transmission to REVERSE (R) for one second, then shift the transmission to DRIVE (D) for one second. 9. Turn the ignition to OFF. 10. Place the transmission shift lever in PARK (P). 11. Release the parking brake prior to towing. 2-40 position (2HI, 4HI, AUTO 4WD or 4LO). 4. After the transfer case has shifted out of NEUTRAL the red light will go out. 5. You may start the engine and shift the transmission to the desired position. Excessively shifting the transfer case into or outof the different modes may cause the transfer case to enter the shift protection mode. This will protect the transfer case from possible damage and will only allow the transfer case to respond to one shift per 10 seconds. The transfer case may stay in this mode for up to three minutes.