Some Questions

[90 Lumina]

Hi all,
I have some questions, got my van back from the transmission shop today, shifts good now. A couple of problems. I have a door ajar light on, it never goes off, even after slamming all the doors. And, at idle the oil light comes on, but as soon as you rev it a little the light goes out, when your driving the light never comes on. Also, I have a Code P1409, where should I start looking??? Thanks everyone,
Ryan

[wiswind]

Door adjar is usually the door switches.
The front 2 doors have the switch located inside the door.....mounted on the bottom of the door LATCH.
I posted a couple of pictures of this switch as viewed with the inner panel removed from the front door.
This switch lights the door adjar light when it is CLOSED (switch is a short when door is open).
Removing the door panel and spraying with some electronic cleaner, or even WD-40 would be my first try at clearing that up.
The Door Adjar switch for the side sliding door(s) is also inside the door, mounted to the bottom of the door latch.
HOWEVER, this switch is OPEN when the door is open....and is 2 of the 4 spring loaded "buttons" on the door that match up with 4 "pads" on the door pillar.......check for bent or sticking spring buttons and clean the pads/button surfaces.......then try the switch as in the case of the front doors.
There are also 2 switches for the rear hatch.

I would get the oil light issue checked out ASAP.
It is possible that you have sludge, etc, built up on the oil pump uptake screen, or some other issue.

P1409 is Electronic Vaccum Regulator (EVR) circuit malfunction.
This is the EGR system and could be a problem with the DPFE.
First thing that I would check is the vaccum line that goes from the top of the EGR valve to the EGR vaccum regulator solenoid, and the vaccum line from the solenoid.....follow all the way to the upper manifold connection.
Also verify that the electrical plug on the EGR vaccum regulator solenoid is plugged in.
Check to see that the electrical connections for the DPFE are plugged in.....and also look around the engine compartment for any wire harness plug that is not plugged in.
In servicing the transmission, it is possible that something was left unpluged, or was bumped.......so that is a good first thing to look for.
Another thing to try is to connect section of vaccum line to the EGR valve vaccum connection and suck on it to manually work the EGR valve.....working it back and forth like this may work loose some carbon bit that could be on the valve seat.....causing a very slight flow when not asked for (if it were much at all.....you would have a very noticable drivability concern from rough running.