2001 GMC Sierra 1500 Pickup Owner's Manual - Page 187

Service 4WD (If Equipped) If the SERVICE 4WD message comes on, there may be a problem with the automatic transfer case and service is required. Cargo Lamp On This message is displayed when the cargo lamp is turned on and the ignition key is turned to RUN. Malfunctions can be indicated by the system before any problem is apparent, which may prevent serious damage to the vehicle. This system is also designed to assist your service technician in correctly diagnosing a malfunction. Low Fuel This message is displayed when your vehicle is low on fuel. Low Washer Fluid This message is displayed when the vehicle is low on windshield washer fluid. The message is only displayed for 15 seconds at the start of each ignition cycle. For more information see, "Windshield Washer Fluid" in the Index. Refer to the fuel gage for a better indication of the amount of fuel remaining in the fuel tank. 2-104