Bedrck47
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OK The definition is “closed loop fault,” which occurs when the processor thinks for some reason there is a problem with one of the upstream oxygen sensors. It could be an issue where the sensor is high or low most of the time or even that misfire activity may be present. The vehicle will continue to maintain a closed loop status, but with a “fault” indicated. It serves as a valuable clue that states the fuel system status must be addressed. The goal of the processor is to protect the catalytic converter with the best possible fuel system strategy.
