Jump to content

Lexus Rx300- Phantom Battery Drain


Recommended Posts


Electrical problem with my 1999 Lexus RX300.

About 4 months ago the battery started going dead within 48 hours of non-use. I had the battery recharged and again...the car went dead. I had it replaced. Same thing. No matter what I tried the problem persisted.

Since then I have had three different mechanics test every electrical system and circuit. All fuses were fine and nothing showed up on the diagnostic meter. I changed the Body Control Module. Still no luck. Finally I purchased a Jump-and-carry.

Please give me any suggestions or insight. I am willing to try anything at this point.

Edited by bswtwa
Link to comment
Share on other sites

  • 1 month later...

I finally found the problem with the electrical system which was draining the battery in my 99 Lexus RX300. It came down to faulty wiring to the back dome light. I removed the burned-out bulb and the problem stopped. When I put a fresh bulb in, the light worked but the battery started draining again. I will have the fixture replaced and see if the problem persists.

I hope this information helps someone else. Please reply to this posting if it does.

Link to comment
Share on other sites


Glad you were able to track down the source of your problem. That's pretty good work!

In the future, you'll find you will problably get more feedback and response by placing your post in the right Forum. In your case that would be the RX forum, somewhat lower down the forum page.


Link to comment
Share on other sites

  • 2 years later...

Hi there!

The problem never really got fixed.  I think it is the door locking mechanism because my key fob stopped working around the same time.  Or it could be a problem with the electrical system that controls the dome lights.  

Here is the method I used to control the problem:

1. I removed all the bulbs from the dome lights and the door bases.

2. I always lock my car.  Even if it is in the garage.  (In the garage I keep my driver's side window open and toss the keys in the front seat). I always open your car door using my key, never the interior button.  That will set off the alarm.

3. I invested in a really good Jump-and-Carry hand held battery jumper and keep it charged in my garage.  If I forget to lock my doors and the battery runs dead, I can hook it up start the car with no problem.  Then I toss it in the back seat just to make sure I don't get stranded at the mall.

Please follow up if you figure out  how to permanently solve this problem.  I would really like to get it fixed.  If you decide to have your door locking mechanism changed let me know if it worked.  

Miss Bret


Link to comment
Share on other sites

  • 4 years later...

Please can someone help me I have a 2006 Rx330 and the battery keeps draining overnight. I changed the battery but it kept happening. I called a mechanic with a scanner he told me is the Oxygen sensor. is that true ?  

Link to comment
Share on other sites

  • 3 years later...

I have a similar problem with my 2000 RX300.  This has been persistent for some time.  The problem is an overnight parasitic drain occurs when I leave my driver's side door and lock assembly connected.  When disconnected, no drainage takes place, regardless of the standing time.  Lexus dealer did circuit tests and determined, or at best, reported, that the problem was the switch and recommended a $1,495.00 switch replacement.  I thought that was a tad high so I subsequently located three other switches which, when tested on my car, gave the same resulting parasitic drain.   Ergo, the switch is probably not the problem.   If anyone in the realm of reasonable land has an answer, I would be happy to pay you for it, providing the remedy works.

Link to comment
Share on other sites

Have you considered taking your vehicle to an Auto-Electric shop for a second opinion? $1495 for a switch replacement looks to be far too much.

Link to comment
Share on other sites

  • 1 month later...

My additional concern (and point of inquiry) would be along the lines of -How much did the st(d)ealership's repair entity charge you for a mis-diagnoses -AND-  that someone in charge of the service department would have been more than happy to pick-your-pocket for that ersatz $1500 mistaken fault with your car?

I have some less than charitable thoughts & feelings for a situation where someone (you?) knuckled under and set the potential-for-thievery loose. Do you really think that if the service department commenced with their 'repair', and it didn't solve the problem that you'd be met with anything other than a shoulder-shrug, or, an invitation to feed them some more cashola? How about if during the journey to collect your $1500, it was 'discovered' that something else (unrelated(?) ) was the culprit, that you wouldn't STILL be roped into paying the full scope of the original mis-diagnoses ?

Having worked an automobile dealership in a facility maintenance manager position (routinely on site before anyone else arrived, and often until everyone else left -daily-) I discerned that there is nary any other type of business that doesn't take unfair advantage of their customer base (AND employees too!) than an automobile dealership.

All in unrestrained scramble for those almighty dollars.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...