1999 GMC Sonoma Owner's Manual - Page 81

yellowblue Shift Light If you have a manual transmission, you have a SHIFT light. CAUTION: If you skip more than one gear when you downshift, you could lose control of your vehicle. You could injure yourself or others. Don't shift down more than one gear at a time when you downshift. If your vehicle has four-wheel drive and is equipped with a manual transmission, disregard the SHIFT light when the transfer case is in 4LO. This light will show you when to shift to the next higher gear for best fuel economy. When this light comes on, you can shift to the next higher gear if weather, road and traffic conditions let you. For the best fuel economy, accelerate slowly and shift when the light comes on. While you accelerate, it is normal for the light to go on and off if you quickly change the position of the accelerator. Ignore the SHIFT light when you downshift. Four-Wheel Drive (If Equipped) If your vehicle has four-wheel drive, you can send your engine's driving power to all four wheels for extra traction. To get the most satisfaction out of four-wheel drive, you must be familiar with its operation. Read the part that follows before using four-wheel drive. You should use two-wheel drive (2HI) for most normal driving conditions. 2-23