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Lexus RX350 Battery Drain Problems

My Mom purchased a new 2011 Lexus RX350 last spring. The dealer installed a remote starter at the time of purchase (we live in Alaska). We've had a continuing problem with the battery going dead if the car has not been driven for a period of time (like 4 days). When she does drive it, it is for short trips (3 miles round trip to work). The original battery was replaced in fall with a heavy duty one, but the problem continues. Its been to the Lexas dealer (130 miles away) several times, but they claim everything is within the tolences and "there is no problem". They did note that the remote starter was drawing more than it was suppose to and reinstalled it. Their finding was that she was not driving it enough and recommened a battery tender, which has been installed. That works as long as she plugs it in daily. However, if a plug in is not available (like at the airport, hospital or if she is visiting) the battery goes dead after 4 days (even after it has been driven 100 miles).

This does not sound right to us, but the Lexus service department has no clue and claims there is nothing in the service bulletins about this problem.

We don't beleive this is what to expect from Lexus. We are about ready to give it back and get a different brand. Any idea's?


  • Are you sure the trunk light is off?

    Something must be drawing power with the ignition switch off. If you know how to use a current meter* , you can probably figure out where that current is going.
    Set the meter to read current in the order of 200mA. With the ignition key off and the doors closed, pull out each fuse and put the meter across what that fuse plugs into. You shouldn't see any appreciable current flowing.
    If one does flow a lot more than any other, that's likely the curprid. Whatever that fuse protects is drawing more current than it should. See what happens after four days with that fuse out. If you can start the car, there's something that needs to be checked.

    (*a multimeter like this has that function:
  • RemcoW.
    This is a good approach but the drain for a 4 day depletion is a bit higher. In alaska it depends on the temperature and I hope the dealer is using battery capacity properly rated for the lower temp range. Many retrofit devices are not properly installed and that is what I worry about. Plus the dealer is not what we call in the lower states LOCAL. If they placed a fuse for the remote start I would just pull that for a few days and see what happens.
  • edited June 2012
    You can't pull a fuse on todays cars and check for a current draw. When doing that you can force a computer/module to go to sleep that may be drawing the current and never find the current draw.

    Instead, leave everything connected and take an infra-red thermal gun and point it at the fuses and relays. If you find a fuse/relay that's hotter than the others, that circuit is drawing higher current than the others and should be investigated first.

  • Tester,
    Almost right. You really cannot see parasitic drain on any infra-red I have used. The heat just dissipates over the copper and the differential is pretty small. I know there are better ones for more money than a person would want to spend. There are fuses perfectly ok to remove without your concerns about clocks and ecu's however. This technique is still valid and you should know this. That said this drain is either larger or the battery less able to provide a larger amp drain.
  • It would depend on the resolution of your thermal gun. I have both high/low resolution thermal guns.

    But there's another way to check for a current draw without pulling fuses. Take a volt meter and measure the voltage drop across the fuses. A fuse with a high voltage drop means the fuse element is hotter than the others which means that's the circuit drawing the current.

  • Tester,
    I was assuming a test at the fuse. I did not make this clear. An amp drain test by pulling the fuse and then testing across the fuse contacts. Not the battery terminals. I should have been clearer.
  • What would help is to know how many milliamps are being pulled; both sans remote starter and with remote in place. One would hope the dealer would have checked this and properly done it should have been put down in writing on the repair order.
  • edited June 2012
    You're not getting it. What if there's a module that isn't going to sleep. If you disconnect the battery or pull a fuse that forces that defective module to go to sleep. And then if you check for a current draw it won't be there. Because you forced the module causing the problem to go to sleep.

  • Module draw is live when it is told to be live. Otherwise our cars would never start. If it is not going to sleep, a rare issue, then you can also pick this up. A thermo scan will not see an active drain easily on a 600ma drain across a 20 amp plastic encased fuse either. But given the mods to this car I would start there and I am sorry if you disagree.
  • Here's the first procedure when checking for a parastic current draw on a modern vehicle. Let the vehicle sit for at least an hour to make sure all computers/modules have gone to sleep.

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