1996LT1Z28

What signals / voltages should I be reading when checking to see if the EGR valve solenoid is on / off. I want to make sure the egr is getting vacuum when it's supposed to.

Thanks for the help.

Injuneer

The solenoid has 12V on the brown wire when the ignition is on. The PCM provides a pulse width modulated ground on the gray wire to send the required vacuum to move the valve to the desired opening. EGR does not operate at WOT, at idle or over 3500 RPM. The degree of opening varies with engine operating conditions.

If the solenoid circuit is faulty it will set a code. If there is no actual EGR flow when there is supposed to be, you get code. The OBD-2 diagnostic will usually pick the lack of flow up. The OBD-1 diagnostic is hit or miss.

You can read the PWM % with a scanner or scan software.

1996LT1Z28

Thanks for the help injuneer!

appreciate it!