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Cars have sensors for manifold air temperature, coolant temperature, manifold air pressure, airflow, throttle position, vehicle speed and oxygen content. All of this electronic wizardry is pretty complicated. So how do you know when there is a problem?
It’s simple – the Check Engine light comes on. The computer monitors all the sensors and uses that information to decide what to adjust such as the fuel mix, spark timing and idle speed. In addition, the computer monitors its own circuits. When it finds a fault, it turns on the Check Engine light and stores a trouble code in the computer.