Am I alone with this? Dead Battery after truck sits for 3 days. 2025 Laramie. 5000 miles. In for service 4 times and it still does it. 1. Replaced the battery, 2. Loose battery cable (sure it was). 3. 10 days in without remedy. 4. Replaced the anti-lock brake module. 5. I have not returned it for service yet.
I have just filed for the Lemon law. I have little faith in the service techs. I searched this forum but no post on this issue.
My Tacoma's battery would die after sitting for a couple of weeks so being an Electronics Engineer I did some research and discovered the newer vehicles have many computers constantly drawing power from the battery. This continual draw is called Parasitic current, and this is what I found for the amount of current draw. “Typically, the normal amount of parasitic draw is
between 50 and 85 milliamps in newer cars and less than 50 milliamps for older cars.”
What I did to determine what my truck was drawing is to connect a clamp meter on DC amp setting. Then I closed all the doors, shut down the engine, removed the key and I was able to watch the current draw go down and finally stabilize at 62 milliamps. Car batteries are designed to have lots of starting or cranking current but very little current for being continuously drawn upon to keep electronics powered up. I looked at my batteries' Amp hour rating and divided it by the 62 milliamps and the result was about 325 hours or around 2 weeks.
If you like to troubleshoot the issue yourself you could connect up the meter then pull out one fuse at a time from each fuse box and see which pulled fuse reduces the current draw, that would be the bad circuit. You might just find one circuit or fuse doing all the power drain or several fuses draining the power. At least you can now go to the dealer and tell them which fuses are causing all the power draw. Just make sure you don't have any electronics powered up or truck doors open which will activate some computers or lights.
You would think the dealer's service department could do this but sometimes the Manufacturer tells the dealers what they can do to troubleshoot trucks and what they are not allowed to do. Perhaps this type of troubleshooting which is very detailed and will take several hours to complete is not allowed. This may be why they tell you they can't find the problem, perhaps the service department doesn't have techs that are trained to troubleshoot or repair the complex electronics.
Next time you go in for service for a dead battery ask them if they have done a parasitic draw test and what are the results that were noted in the service log. Make sure you get the results, that will show they did the test. If it is above the limits ask them what troubleshooting they did to find the source of the draw. The steps above are the easiest way to single out the cause, if they didn't do it then ask what steps they did do to find the source of the current draw.
Good luck and hope novel this didn't put you to sleep.....