94 LeSabre check engine light, codes not retained

This is about my sister's car that I am trying to get back into decent shape. The check engine light comes on sometimes. It can be days before it comes on or sometimes it comes on in the driveway. I feel like a surge and the light comes on, it will stay on until the car is turned off (then it goes away). I have taken it to a few places trying to get the codes but they are not being retained. Any ideas?

Also, I'm assuming the 3.8 has a PVC valve. Could someone tell me where it is?
One last thing, the heater/ac only blows from the defrost. Is this a broken vacuum line or someting?

1. Your heater/ac unit runs on engine vacuum. There is a small rubber hose going to the engine firewall below and to the left of the master cyclinder. This usually falls off or dry rots. Without it, the air will only blow out the defrost vents.
2. I believe the PCV is located on the back side of the throttle body unit.
3. A CES light means a code is present. If it is not being retained, you can download the code yourself immediately after shutting the car down when the light was on (i.e. before it resets). The procedure is to use a jumper wire and connect two pinouts in a connector found under the dash, under the radio/ash tray, then turn the ignition to the 'on' setting. The ECM goes into diagnostic mode and outputs any codes.
The following link gives an in depth expaination:

http://www.geocities.com/dann8785/serviceenginesoon.html