I recently bought a 2005 Cadillac CTS and I have had problems with some electrical systems. The gas and fuel gauge don't work and the car thinks it is constantly in drive since some of my navigation features (like playing DVDs) are disabled because they are "unavailable when the vehicle is in motion". The lights on the automatic gear shift do not illuminate to tell you which gear the car is in. The reverse lights also do not work and the key gets stuck in accessory mode. I have to manually remove the key by pressing the release button under the steering wheel. The theft light is on and so is the traction control dummy light. The radio constantly displays the message "Service Theft Deterrent System." I recently discovered that the 3rd rear brake light (the one that goes over the trunk, not the legal lights) was full of water and also does not work. I have checked fuses, tried disconnecting the battery, & touching the battery cables together to reset all computer systems as I read on the Internet. I have read online that this is apparently a problem with the ECM or with any of the 8 modules connected to/contained in the BCS. I have been led to believe that the DIM (Dash Integration Module) or the RIM (Rear Integration Module) is faulty (or has a faulty component) but I am not sure how to test this or how to proceed once I find the answer. The car had its ECM (Electrical Control Module) replaced in August 2014 (according to the CarFax) and the battery is new as of June 2014. Any suggestions?