1990 Cadillac Deville 1990 Cadillac Devile NO LIGHTS TO THE

I see your dilemma, and I will get back to you after some research. Tonight was a busy night, and I am just tying some loose ends right now. I have access to a factory service manual for your vehicle, and if you don't hear from me through the afternoon, it will be tomorrow evening at the latest.

The BCM is not part of the exterior lighting circuits on this vehicle. I did some research, and photocopied some information for my reference as we go along. In looking at the schematic, all of the affected circuits you mention share a couple things in common. But first, I need to establish some knowledge of what you've done so far. How have you determined these circuits have no power, was it with a test light? That would be the simplest of methods, and perfectly capable. One thing to consider is, was the test light working when you tested? If you have a poor ground to the light, or you don't function check it on a known good circuit to see that it lights, it can give you wrong info and send you on a goose chase. So, if it is a test light, you need to make sure it is functioning, and can be trusted at the time of testing.

Where did you test to determine that no power exists, at the sockets? All the circuits you mention, as I said, have a couple things in common. The all pass through connector C400, which is shown to be a 6 pin connector that is in the trunk behind the RH(passenger) wheelhouse. I don't have an end view that shows all the wires, but I do show by schematic info that; Pin A yellow, Pin B dark green, Pin D brown, Pin E light green, and Pin F is black. Pin C is unknown, and may be empty, but regardless, all the circuits pass through C400 so check it.

You mention that you have ground everywhere, How was this checked? The reason I ask is that all these circuits share a common ground, with exception of he LH rear side marker, which grounds at G200 at the left I/P shroud for some reason. The ground they all share is G402, which is in the RH rear of trunk, on rear of the wheelhouse, and probably next to C400. Check that this ground is clean and tight.

If this don't point you to a cause, then it will be down to checking wires. I have a hard time believing that you have three open wires, unless they are cut where they route together as a harness. That is if you truly have no power, and the ground is good. If you have a 194 bulb, place it in that left rear side marker lamp and see if it works. The brown wire that feeds it does not pass through C400, and like I say it is grounded at G200, which also, for the sake of reference, grounds your turn signal indicators in the cluster. I think you're going to find your problem at C400, or G402, though.

Good luck, and let me know.

I don't know what connector your testing at, but C400 is in the trunk. Have you pulled the lining away from the sides to expose the wheel house? The harness should run down the door sill, I would speculate the left side. Come up under the rear seat cushion and enter the trunk. It will exit the trunk through individual pass through grommets. It sounds like you may be testing at one of the rear lamps, to body harness connectors.