Open loop operation means that the ECU is not correcting the air/fuel ratio based on oxygen sensor information. The ECU ignores exhaust oxygen sensor information even if the sensor is detecting an excessively rich or lean mixture. There are certain operating conditions where it is not desirable to operate the system in closed loop due to risk of catalyst overheating and driveability concerns. These conditions are:
• Engine starting
• Cold engine operation
• Moderate to heavy load operation
In open loop operation, a correction coefficient of 1.0 is used.
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