Circuit Description

Ignition voltage is supplied directly to EGR vacuum control signal solenoid. PCM controls the solenoid by grounding the control circuit through an internal switch called a driver. The primary function of the driver is to supply ground for the component being controlled. Each driver has a fault line which is monitored by the PCM.

When PCM is commanding a component ON, voltage of the control circuit should be low (near zero volts). When PCM is commanding the control circuit to a component OFF, voltage potential of the circuit should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, the fault line status will change, causing DTC to set.