DeVille Battery Drain Causes Multiple System Failures

Having dealt with similar electrical gremlins in my 2005 Cadillac CTS, I can share my experience. I have some experience working on cars, mainly basic maintenance and electrical troubleshooting. The symptoms you describe match exactly what I experienced, multiple error codes, flickering lights, and battery drain issues. After taking my CTS to the workshop, they diagnosed a faulty battery sensor which was causing incorrect readings and leading to battery failure. The battery sensor was unable to properly monitor the charging state, resulting in a continuously discharged battery despite the alternator working correctly. The repair involved replacing the battery sensor and performing a full system diagnostic to ensure no other components were affected. Total cost was 315€ including parts and labor. Before jumping to conclusions though, could you share: How old is your current battery? Do you see any corrosion on battery terminals? Does the alternator belt look intact? Are there any specific error codes showing up? This information would help determine if your DeVille is facing the same battery drain issue or if there might be other electrical problems at play. A proper diagnosis would prevent replacing parts unnecessarily.

Thank you for sharing your advice. My car recently had its service at 63640 KM and the battery terminals were actually cleaned during that visit. The current battery is just over 4 years old. After checking your suggestions, I noticed some light greenish residue building up again on the negative battery terminal, which could indicate a low battery issue. The alternator belt looks fine with no visible wear or cracks. The main error codes showing are P0562 and P0563, which from what I understand relate to system voltage being too low and too high respectively. This makes me suspect the charging system might be acting up beyond just a simple vehicle battery problem. I appreciate the cost reference for your repair. Given the similar symptoms, I will have the battery sensor checked along with testing for any battery drain when the car is off.

Thanks for the additional details about your DeVille. The green residue on the battery terminals definitely points to ongoing corrosion issues, which can cause poor electrical connections and contribute to a weak battery situation. Those voltage-related codes (P0562/P0563) are exactly what I saw on my CTS before discovering the faulty sensor. The alternating high/low voltage readings typically suggest the charging system is getting incorrect information, leading to improper battery charging cycles. In my case, cleaning the battery terminals only provided temporary relief. The battery sensor was still sending wrong signals, causing the system to either overcharge or undercharge the battery. This created a cycle where the battery would gradually lose its ability to hold a charge. Given how similar your symptoms are, I strongly recommend having the battery sensor tested first. A new battery alone might not solve the issue if the sensor is faulty. My repair started with replacing the sensor, then we found the battery had been damaged from improper charging and needed replacement too. Total ended up being around 480€ for both parts with labor. Would be useful to know if your battery shows normal voltage when tested directly at the terminals with a multimeter while the engine is running. This could help isolate whether its a dead battery issue or a charging system problem.

Thank you for the followup suggestions. I just checked the voltage at the battery terminals using a multimeter as recommended, it shows 11.8V when the engine is off and jumps to 14.9V when running, which seems a bit high from what I understand about normal charging voltage. The error codes combined with these voltage readings definitely point toward a charging system issue rather than just a discharged battery. I will have both the battery sensor and charging system checked professionally since I dont want to risk damaging a new battery by installing it with a faulty charging system. The battery terminals will need another proper cleaning too given that corrosion is already building up again so soon after service. I suspect the high charging voltage might be accelerating the corrosion process. I appreciate you sharing your detailed repair experience. Getting both the battery sensor and battery replaced at around 480€ actually seems reasonable considering all the electrical issues it could resolve. Will book it in for diagnosis next week and hopefully have similar success fixing these electrical gremlins.