What is the flow of sensors in a car?

Answer 1

I guess you mean the order of operation in an engine control system. Actually you can look at this from a couple of different standpoints. First, sensors themselves. As the air is drawn into the egine, it's temperature and amount are measured by either some kind of airflow meter, or a manifold pressure sensor, and an intake air temp sensor. Engine coolant temp is measured by either an engine coolant temp sensor or a cylinder head temp sensor. On some vehicles atmospheric conditions are measured by a baro sensor. EGR position or flow is measured with either an EGR position sensor, EGR temp sensor, or some type of flow sensor. Fuel tank pressure is monitered with a fuel tank pressure sensor for evaporative emmissions requirements. Some vehicles have a Transmission Fluid temp sensor to measure that. Crankshaft and camshaft position is monitered with those corresponding sensors. Oxygen sensors in the exaust help the PCM determine how rich or lean the engine is running by measuring exaust gases, and the catalyst moniters measure catalytic converter activity. Vehicle speed or wheel speed sensors measure the speed of the vehicle and output shaft speed sensors on the transmission help the PCM determine transmission functions. Those are the ones I can think of off the top of my head, but that only covers sensors. An engine ctrol system has actuators and solenoids also. So one can look at things from a control standpoint as well.In a nutshell that flow is sensor-decision-actuator-moniter.In other words, the info is gathered by the PCM using the sensors around the engine. A decision is made and actuators are used to carry out that decision. Those actuators include fuel injectors, idle air control solenoid, transmission shift solenoids, cooling fan and AC relays, and more.Then the sensors are again used to moniter the effect the decision has made. Then the decision process starts again. This happens hundreds of times a second, and on top of all of this, a diagnostic system is in place constantly monitering everything. The diagnostic portion of the PCM actually operates as a separate entity, though still being very much a part of the whole thing. It is kind of like big brother looking over the shoulder of the control part of the PCM. When a check engine light comes on, it is the diagnostic part of the PCM that has turned it on due to some conflict it has seen.

Sounds simple doesn't it?