The answer is in the name; An oxygen sensor measures the amount of unburned oxygen in the exhaust system left after combustion in the engines cylinders. Based on the amount of Oxygen present, the sensor genrates a voltage which is read by the engine's fuel management system. Too much residual O2 in the exhaust, and the Jeep's computer releases more fuel for the next combustion cycle; too little O2, and the opposite happens. This balancing act happens many times every second to maintain the optimal fuel to air ratio of 14.7
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