This 2011 Cadillac DTS came in with the complaint that the battery will go dead if the car sits for more than 12 hours. I traced the drain to the Driver’s Door Module fuse (DDM) in the rear underseat fuse block. I used an amp meter connected in series between the battery negative terminal and the battery negative cable. I followed this with a millivolt drop test across all fuses until I located and removed the suspected fuse from it’s circuit.
Standard operating procedure is to start testing at the battery and fuses. In hind site there was a much easier way to locate the suspect condition so in this post I am not going into all of the testing that I had to do to isolate the root problem. With the ignition off, observe the lights on the power mirror selector switch. The amber light would come on and a very light click could be heard in the DDM asssembly. The click was much louder and easier to hear with the DDM switch assembly removed. DDM stands for Driver’s Door Module.
The DDM can be removed from the door panel by sliding a small screwdriver or similar plastic tool under the leading edge of the DDM in order to depress the locking clip. There is a second clip at the rear of the DDM. I am showing the clip with the DDM removed from the door panel so you can have a better view of the clip.
I checked wiring diagrams and connector pin outs in order to better test the voltage signals. I found that I could remove the green data line wire from the connector and the problem would go away. The trouble was that this signal was a symptom and not the cause of the problem. It took a great deal more testing than I can get into here to find the actual cause. The problem was really located on the orange wire that goes between the DDM and the Memory Seat Module Recall Switch.
To get to The Recall Switch the door panel needs to be removed. The trim panel behind the interior door handle had to be removed. I used a small screw driver to pop the panel out.
Once out of the way the hidden screw could be removed.
The next step is to go around the outside edge of the door panel and pull the panel loose from the door. There are quite a few of the push pin style retainers behind the door panel. Because of the design you have to push the limit between pulling hard enough to release the clips and hard enough to break the door panel.
Once all of the retainers are loose around the outside edge of the door panel, the panel needs to be lifted straight up about an inch or two. Then the panel will come loose from the door. In the next two pictures are images of the two steel retainers that secure the center part of the panel to the door. When the panel is properly removed those clips will be retained in the door panel. After the panel is removed the retainers have to be removed from the door panel and…
….. reinstalled onto the plastic tabs located on the doors interior. If you try to pull the interior area of the door panel any direction except straight up the plastic components will be broken.
The memory recall switch assembly is held in place on the door panel by clips along its outer edge. It can be gently pried loose with a small screwdriver. The switch assembly can then be disassembled in the same manner.
Looking closely in the next picture you will see green corrosion on the circuit board. Just above the three resistors in a row. Click on the picture to enlarge. The only thing that had to be done to fix this problem was to use a plastic bristle brush to clean the corrosion from the circuit board. The cause of the corrosion was likely one of a few things. Rain from a window being left down, rain from the door being opened repeatedly while raining or over zealous use of liquid cleaners on the door panel.