EGR System: Operation: Notes

On 5.2L engines, electronically controlled EGR system is used. The system consists of Spark Control Computer (SCC), Charge Temperature Sensor (CTS), EGR solenoid and EGR delay timer (4-Bbl. models).

On 5.2L 2-Bbl. engines, ported vacuum is routed through a CVS on the thermostat housing to the EGR solenoid. The CVS opens at about 108-125°F (42-52°C), allowing vacuum to the EGR solenoid.

Venturi vacuum control system is used for EGR operation on 5.2L 4-Bbl. engines. Because of the low strength of venturi vacuum signal, a vacuum amplifier is used to increase vacuum signal strength to operate the EGR valve. This system uses an EGR solenoid to control EGR valve operation. Some vehicles are equipped with an EGR delay timer to prevent EGR operation for about 60 seconds after ignition is turned on.