1. Engine Temperature Sensor: The engine temperature sensor monitors the temperature of the engine coolant. When the engine reaches its optimal operating temperature, the sensor sends a signal to the PCM.
2. Oxygen Sensor: The oxygen sensor measures the amount of oxygen in the exhaust gas. When the engine is running lean (too much air and not enough fuel), the oxygen sensor sends a signal to the PCM. When the engine is running rich (too much fuel and not enough air), the oxygen sensor sends a different signal to the PCM.
3. Throttle Position Sensor: The throttle position sensor monitors the position of the throttle plate in the throttle body. When you step on the gas pedal, the throttle plate opens, allowing more air to flow into the engine. The throttle position sensor sends a signal to the PCM indicating the throttle plate's position.
4. PCM (Powertrain Control Module): The PCM receives signals from the engine temperature sensor, oxygen sensor, and throttle position sensor. Based on these signals, the PCM calculates the appropriate EGR valve position to optimize the engine's performance and emissions.
5. EGR Solenoid: The EGR solenoid is an electronically controlled valve that regulates the flow of vacuum to the EGR valve. When the PCM determines that the EGR valve should open, it sends a signal to the EGR solenoid. The solenoid then opens, allowing vacuum to flow to the EGR valve.
6. EGR Valve: When the EGR solenoid opens, vacuum is applied to the EGR valve, causing it to open. This allows a small amount of exhaust gas to be recirculated back into the engine's intake manifold. This helps to reduce the formation of nitrogen oxides (NOx) emissions.
So, the PCM controls the EGR valve by sending a signal to the EGR solenoid, which in turn opens or closes the EGR valve based on various engine operating conditions.
