[2slo]

Hi all,
I am working on a new-to-me 2000 SC2 with a 1.9L DOHC engine. The check engine light is on and my scanner reveals P0405 code.
I have read numerous posts on this site about cleaning the EGR valve and ports and have done so several times only to have the code reset within a moment or so. In one post in particular the pin-out for the valve was listed. The post stated that the valve receives 2 voltage sources: 1) a 5v source for the sensor position and 2) a 12v source for the servo motor that moves the pintle. When I remove the connector from the EGR valve and probe the connector I read 5v on the 5v source. Using a 12v test light from the 5v source to ground causes the light to glow. With the connector attached to the valve the 5v remains. So far so good.
When I probe the connector for 12v I only read 8.5v. A test light hooked from the 12v supply wire to ground fails to light and the 8.5v goes to 0v. Further, if I reconnect the wire to the EGR valve the 8.5v goes to 0v. I checked for a short from the 12v pin on the EGR valve to ground and none exists.
From where is this 12v derived? Has anyone else experienced this issue? Where can I find a wiring diagram to aid in trouble shooting this problem?