2001 GMC Sierra 1500 Pickup Owner's Manual - Page 186

Check Eng Oil Pressure This message is displayed when the engine oil pressure is low. Change Engine Oil This message is displayed when the engine oil needs to be changed. The message is only displayed for 15 seconds at the start of each ignition cycle. When you change the engine oil, be sure to reset the Engine Oil Life Monitor. See "Engine Oil, When to Change" in the Index. See "Oil Pressure Gage" in the Index for more information. Check Eng Oil Level (Gasoline Engine) This message is displayed when the engine oil level is low. Security This message is displayed when the content theft-deterrent system has been activated and also monitors the PasslockR System. If the security message is displayed continuously while driving and stays on, there may be a problem with the Passlock System. Your vehicle will not be protected by Passlock, and you should see your GM dealer. Once oil is added, it may need time to drain and settle in the engine before this message will turn off. It is best to let the engine cool down (if it is hot) or warm up (if it is cold) and cycle the ignition to be sure this message turns off. Refer to the dipstick for the correct level. See "Engine Oil" in the Index on how to check the oil level and for what type of oil to add. 2-103