I get a constant beeping. Some days it will not beep. I get occasional beeps also. There is no pattern for these beeps. I live at 6800 feet above sea level but it will beep at all altitudes so it may not be an oxygen sensor. I had it replaced a year ago. I have checked all fluids and changed the air filter. Sometimes it has a slow startup for a couple of seconds. The Interstate battery is only a few months old.