Dead Battery in my Cayenne? Quick Diagnosis Help Needed

Hi! I had a really similar issue with my 2006 Porsche Macan (I have some experience with Porsche vehicles). The symptoms were exactly like yours, weak starts, flickering lights, and battery problems. Initially thought it was just the battery, but turned out to be a faulty control unit that was draining the battery even when the car was off. Took it to my trusted workshop, and they diagnosed it after some thorough testing. Cost me around 600€ to get the control unit replaced, but it fixed the problem completely. No more battery issues since then. Before I share more specific details about my repair, could you tell me if you've noticed any other electrical issues? Also, have you checked if the battery drains when the car is parked overnight? This info would help me understand if you're facing the exact same problem I had. Hope this helps! Mike

Hey Mike! Thanks for sharing your experience! My last service was just 2 months ago at 91151 KM, and they didn't mention any issues with the control unit. But what you're saying makes a lot of sense, I've actually noticed the battery seems to drain pretty quickly even when the car's just sitting in the garage overnight. I'll definitely get it checked for that control unit issue you mentioned. Better to catch these things early than end up stranded somewhere! Would you mind sharing which specific control unit it was in your case? Just want to give my mechanic a heads up when I take it in. Cheers

Hey! The control unit that caused trouble in my Macan was the Body Control Module (BCM). It's basically the brain that manages all the electrical systems in the car. In my case, it wasn't shutting down properly when the car was off, which kept draining the battery. The overnight drain you're experiencing sounds exactly like what I went through! I actually did a little test before taking it to the shop, I used a multimeter to measure the battery drain (had a mechanic help me with this). It was drawing about 85mA when it should've been under 50mA. That's what got me suspicious about the control unit in the first place. One thing I forgot to mention earlier, before the control unit replacement, I tried jumping the battery and even replaced it with a new one, but the problem kept coming back. The symptoms would improve for a few days and then start again. If you're experiencing something similar, it's probably the same issue I had. Let me know how it goes when you get it checked out! Always happy to share more details about my experience if you need them. Cheers, Mike

Thanks so much, Mike! That's super helpful info about the BCM! It really does sound like we had the same issue. Come to think of it, I did notice the battery would seem fine for a few days after a jump start, but then go back to acting up, just like you mentioned. I actually have a multimeter in my garage, so I might try checking that drain rate myself before heading to the shop. I'll make an appointment with my mechanic tomorrow and specifically mention the BCM issue. Will definitely keep you posted on what they find. Thanks again for all the detailed info, it's going to save me a lot of time troubleshooting! Cheers