Computer Command Control - Throttle Body Fuel Injection

Wiring Diagram for EGR Circuit:

The EGR is controlled by a vacuum solenoid that uses "Pulse Width Modulation." The valve allows the ECM to turn ON and OFF the solenoid many times a second. The ECM varies the amount of ON time (Pulse Width) to change the amount of exhaust gas flow. The Coolant Temperature Sensor (CTS), Throttle Position Sensor (TPS), and PARK/NEUTRAL switch transmit signals to the ECM in order to regulate the EGR solenoid. During cold and idle operations, the solenoid circuit is not grounded by the ECM, which does not allow vacuum to flow to the EGR valve. The amount of exhaust gas flow depends on manifold vacuum and variations in exhaust back pressure.