open loop VS closed loop ecu modes

ECU Modes:

OPEN LOOP - this is the mode your ECU is in until the coolant temperature and a couple other sensors get to operating values. This is also true when you are at WOT or when throwing codes/ CEL's

CLOSED LOOP - the ecu uses information primarily from the Oxygen Sensor and adjusts fuel delivery and timing to achieve minimum emmisions, better gas mileage and power.