Circuit Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The engine control module (ECM) uses an exhaust gas recirculation (EGR) vacuum vent solenoid and an EGR valve vacuum control solenoid to control the position of the EGR valve. When the EGR valve is desired to open, the EGR vacuum vent solenoid is commanded open and the EGR valve vacuum control solenoid is commanded open. This will allow vacuum from the vacuum pump to open the EGR valve. When the EGR valve is desired closed, the EGR valve vacuum control solenoid is commanded closed and the EGR vacuum vent solenoid is commanded closed. When the EGR vacuum vent solenoid is commanded closed, the EGR vacuum control system is vented to atmosphere which causes the EGR valve to close very fast. The EGR vacuum vent solenoid is supplied 12 volts by the ignition 1 voltage circuit. The EGR vacuum vent solenoid is controlled through the EGR vacuum vent solenoid control circuit by the ECM. If the ECM detects a high voltage condition on the EGR vacuum vent solenoid control circuit, DTC P2145 sets.