1998 Lexus ES300 Electrical Problem

My wife loves this car except when it won’t start, and unfortunately that’s happened from time to time recently. The first time was when we were out of town, when we got home, it wouldn’t start. No big deal. But since then, it’s developed the habit of draining the battery over very short times. We put in an after-market stereo a couple years ago, I thought that must be the problem. Pulled the fuse so it wouldn’t play. Overnight the battery ran down. The battery is almost new. I took it back to the seller of the battery and had it checked. It’s fine. My nephew told me that when he had a 1998 ES300, it had a similar problem. Obviously some type of battery drain, but I’m at a loss. Suggestions welcome. The Lexus dealer cannot diagnose the problem.


Has anybody performed a proper parasitic draw test?

Unless somebody SPECIFICALLY told you they did, I’d assume they did not

By the way, did anybody check the charging system

Just because you have a draw, doesn’t mean the alternator is good

Bring it to some one who can test for a parasitic current draw.

A parasitic current draw occurs when a computer/module fails to go to sleep after the vehicle is shut off. Which drains the battery down.

These type of current draws can be hard to locate. But anyone who’s worked around modern vehicles with their modules and computers will locate it.


“A parasitic current draw occurs when a computer/module fails to go to sleep after the vehicle is shut off. Which drains the battery down.”

I agree, but modules aren’t the only thing that cause a draw

Shouldn’t a Lexus service department be able to figure this out? Our local dealer has not been able to diagnose the problem. How do I find someone else to do necessary testing?

“Shouldn’t a Lexus service department be able to figure this out? Our local dealer has not been able to diagnose the problem”

Much depends on the experience, knowledge, and determination of the guy working on the car

If the young, inexperienced, impatient guy is working on the car . . .

Just because you pulled the fuse on the new aftermarket stereo system does not mean it doesn’t have a high resistance short to ground. The best recommendation I can offer is to take it to a shop that specializes in auto electrical systems. They’ll have the schematics and the expertise to track down the problem And be sure you tell them about that aftermarket stereo installation.

Just out of curiosity, when you installed the system did you use an adapter plug? Or did you splice the wires? Aftermarket installations that are spliced in are a common sourceof electrical problems.

Thanks for your comment. Unfortunately, I don’t entirely understand it. If the fuse is pulled on the stereo, can it still be a cause of the problem? I thought I had eliminated that, or at least learned that there was another cause (perhaps in addition to the stereo).

I didn’t install the stereo. It was installed by what I thought was the best place shop in the area. I don’t know if they used an adapter plug or spliced the wires. It’s really hard to get access to the back of the stereo in this car.

I think you’re right about finding a good shop. I’m looking around for one now.

Audio systems can use more than one fused power circuit to supply power to it. There are also many other things that can cause this kind of problem but it is usually fairly easy to figure out where the problem area is at using the proper proceedures. Here is a link you can refer to see how the service is done.


The dealer shop should be able to solve this, but remember their focus is on doing warranty work, and that will be for cars less than 3 years old for the most part. So that is what the dealer shops are most expert at, 3 year old or newer cars. I’m sure though they could solve it if you left it with them and a cashiers check for $10,000 as a retainer to cover however much time it takes them to debug the problem. They’d refund whatever money in the account is leftover of course … lol …

The above is only semi-joking. I think the reason the dealer is reluctant to spend too much time on this is b/c they see the aftermarket items installed and they think it will take a lot of time and they are concerned they’ll make you, a Lexus customer, upset when the bill is presented. If you can assure them you’ll be happy when it is fixed no matter how much it costs, then I expect they’ll be happy to let you leave the car with them and eventually they’ll find the problem.

I’m with the posters above, unless the above idea works for you, you would be better off to have a specialist auto-electric shop solve this for you. They have the proper test equipment and staff expertise and do this kind of stuff routinely.

If you wanted to do a little scientific work yourself, you could use this as an excuse to buy one of those fancy laser-temperature gadgets. Point the laser at each fuse one by one to see which is the circuit that is drawing the most current. That fuse will be the hottest.