Exhaust Gas RECIRCULATION, Diesel: Operation

When the Powertrain Control Module (PCM) supplies a variable ground signal to the Exhaust Gas Recirculation (EGR) vacuum valve solenoid, EGR operation begins. The PCM monitors and determines when to supply and remove the variable ground signal. This will depend on inputs from the engine coolant temperature, throttle position and engine speed sensors.

When the variable ground signal is supplied to the EGR vacuum valve solenoid, vacuum from the vacuum pump will be allowed to pass through the solenoid and on to the EGR system, by a connecting hose.

Exhaust gas recirculation will begin in this order when:

• The engine is running.
• The PCM determines that EGR system operation is necessary.
• A variable ground signal is supplied to the EGR vacuum valve solenoid.
• Variable vacuum passes through the EGR vacuum valve solenoid to the EGR system.
• The inlet seat (poppet valve) in the EGR valve opens to dilute and recirculate exhaust gas back into the EGR cooler manifold.
• Coolant flow through the EGR cooler is controlled by the EGR wastegate valve solenoid.

The EGR system will be shut down by the PCM after 60 seconds of continuous engine idling to improve idle quality.