Open Loop Operation

OPEN LOOP OPERATION

At times (start-up, full throttle) engine operating requirements may fall outside the bounds of that suggested by the ECM inputs. Some sensors do not operate at peak efficiently until warm. At these times, the ECM substitutes a preprogrammed set of reference inputs that are most likely to produce desired engine operation. This is referred to as open loop operation.

The system may also default to open loop operation when component failure provides an input signal outside the range of known parameters recognized by the ECM. The ECM will substitute a signal value that allows the vehicle to continue to operate. The Malfunction Indicator Lamp (MIL) on the instrument panel is illuminated at this time to indicate the failure of an emissions-related component.