EPR Solenoid & Valve
EPR valve partially restricts exhaust to provide backpressure necessary for proper operation of EGR. EPR solenoid controls vacuum to EPR valve. Supply voltage for EPR solenoid comes from ignition, and ECM energizes EPR solenoid by grounding circuit inside ECM.
EPR circuit is turned off by ECM until coolant temperature sensor sends a signal that engine temperature is above 104° F (40°C). ECM will not recognize an electrical fault in EPR circuit, but will recognize vacuum leaks preventing operation of EPR valve.