Theory Of Operation

The EGR Valve Assembly contains an electric DC motor and gear box. An eccentric drive translates the gearbox output from a rotating motion (DC motor) to a linear stroke (output shaft). An internal return spring ensures that the valve returns back to its closed position as a fail safe.

• During initial opening of the EGR Valve, the PCM drives the PWM voltage high resulting in a high current draw. After the valve is fully opened the PCM voltage is reduced to maintain the EGR Valve position. This reduces the current draw and protects the DC motor from overheating.
• The PCM also applies a current in the closing direction to fulfill the required dynamic performance. This is done to slow down the closing speed of the shaft near the stop. This ensures that the valve does not close too fast causing the valve disk to be forced into the stop harshly which may damage the internal gearbox.

There is a position sensor located on the output shaft. The sensor operates as a typical three wire sensor, with a 5-Volt Supply, Sensor Signal, and Sensor Ground circuit.