Controles eletrônicos do motor – Funcionamento do sistema e componentes

Electronic Engine Controls – 2.5L Duratec-HE (122kW/165PS) 303-14A-7 303-14A-7 - MI4 DESCRIPTION AND OPERATION The heated oxygen sensors age with mileage, increasing their response time to switch from rich to lean and lean to rich. This increase in response time influences the ECM closed loop control and leads to progressively increased emissions. Measuring the period of rich to lean and lean to rich switching monitors the response rate of the upstream sensors. Diagnosis of electrical faults is continually monitored in both the upstream and downstream sensors. This is achieved by checking the signal against maximum and minimum threshold, for open and short circuit conditions. If a heated oxygen sensor fails: The ECM defaults to open loop fueling for the related cylinder bank The CO (carbon monoxide) and emissions content of the exhaust gases may increase The exhaust may smell of rotten eggs (hydrogen sulphide). With a failed heated oxygen sensor, the engine will suffer from reduced refinement and performance. Engine coolant temperature (ECT) sensor E135523 The ECT sensors are NTC (negative temperature coefficient) thermostats that allow the ECM to monitor the engine coolant temperature. There are two identical ECT sensors installed, which are identified as ECT 1 and ECT 2. Each sensor is secured with a twist-lock and latch mechanism, and is sealed with an O-ring. A two pin electrical connector provides the interface between the sensor and the engine harness ECT 1 ECT 1 is installed in the heater manifold, at the rear of the RH (right-hand) cylinder head. The input from this sensor is used in calibration tables and by other systems. If there is an ECT 1 fault, the ECM adopts an estimated coolant temperature. On the second consecutive trip with an ECT 1 fault, the ECM illuminates the MIL (malfunction indicator lamp). ECT 2 ECT 2 is installed in the lower hose connector which attaches to the bottom of the thermostat. The input from this sensor is used for OBD (on-board diagnostic) 2 diagnostics and, in conjunction with the input from ECT 1, to confirm that the thermostat is functional. If there is an ECT 2 fault, the ECM illuminates the MIL on the second consecutive trip. Manifold absolute pressure and Temperature (MAPT) sensor E135524 In the MAPT sensor housing are located a piezo-pressure sensor element (MAP (manifold absolute pressure) sensor) and the electronic circuits for signal amplification and temperature compensation. The IAT sensor element is an NTC (negative temperature coefficient) resistor. A special coating process renders the MAP and IAT sensor elements resistant to damp and humidity in the intake pipe. The MAPT sensor receives a reference voltage of 5 Volts from the PCM. The output signal from the MAP sensor element is an analogue voltage signal which changes proportionately to the absolute pressure in the intake manifold. A high absolute pressure in the intake manifold (throttle valve wide open) means a high voltage, and a low absolute pressure in the intake manifold (throttle valve closed) means a low voltage. With ignition on and wide-open throttle the MAP sensor measures the BARO (barometric pressure). The resulting value is stored in the Keep Alive Memory and serves as a reference pressure