| You said.. "When you are at idle or cruising down the highway, the ECU turns on the EGR solenoid" EGR solonoid is off ("on" see below) at idle. Only under load while cruising under certain throttle position is the EGR allowed to flow.
The off condition of the EGR solonoid is "open" or allows vacume to pass thru it.. The EGR solonoid receives 12volts from the battery all the time
The other side of the solonoid recieves a ground or 12 volts from the ECM to turn it off or on. When no EGR is wanted there is a power from the batt and ground from the ECM. Solonoid "on" = "No vacume Flow" When EGR is called for, the ECM sends battery voltage to the other side of the solonoid to effectivaly turn it "off"="Vacume flows" Basically on is off, off is on if you get what I am saying. The ECM grounds the solonoid normally to close it. When it wants EGR vacume the ECM applies 12 volts to the other side of the solonoid to make it off or "open". If the Electrical connection to the solonoid is bad the EGR will flow whenever there is a vacume sorce from the T/B.
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