1999 Dodge Caravan check engine light

The vehicle's spark and fuel systems are constantly monitored by the PCM and it is self diagnosing a problem in a sensor, input value, or response to a command. The check engine lamp is it's way of letting the driver know the vehicle needs diagnostic service. Of course another diagnostic computer is used for this function. It is called an electronic scan tool. Chrysler called it a DRBIII. Diagnostic Readout Box. This is the preferred way to repair according to the manufacturer. It is quite efficient at locating a possible larger failure that is more expensive and Federal Law requires the emmisions to be tested and repaired. Ok