2000 LEXUS RX 300 RX300 BATTERY DRAIN

  • Tiny
  • wildron
  • 2000 Lexus RX 300

Electrical problem
2000 Lexus RX 300 6 cyl All Wheel Drive Manual 78000 miles

The battery in my Mom's RX300 goes dead if not driven for about two weeks (she has another car). I has traced a parasitic current draw down to two circuits. With the ammeter connected to the negative battery cable and the battery post (cable disconnect), I get 0.596 amps. With DOME fuse removed I get 0.300 amps. If I remove the ECU-B fuse I get 0.387 amps. No lights in the DOME circuit are on, I checked them all. No check engine light is all. Everything works fine and if driven everyday the battery stays fine. I assume the ECU-B requires current to operate the alarm system when the ignition is off. If the problem is in the DOME circuit I have not idea how to diagnose the problem. Any advice would be greatly appreciated.

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Saturday, May 30th, 2009 AT 12:10 PM

3 Replies

  • Tiny
  • Docfixit
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  • 18,993 posts

Are you using the milli amp scale or 10 amp? A.5 milli amp is about right for that car but.5 amp is not
Does car have vanity mirrors? If so see if on when lid shut also ckeck trunk light and glove box.

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Saturday, May 30th, 2009 AT 12:27 PM
  • Tiny
  • wildron
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Yes, I'm using the 10 amp scale. I've checked all the lights, both dome lights, the glovebox, light, the vanity lights. I've even checked the car at night. I can't find any lights on. I'm suspecting the body ECU, but I don't know how to check it. Any ideas?

I'm little confused here. Using my mutilmeter I get about 0.6 amps when I connect the leads to the negative battery cable and the post. When I switch to the mA scale (changing the leads on the meter) I get about 0.15. What am I doing wrong? Shouldn't I be getting about 600 milliamps?

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Sunday, May 31st, 2009 AT 12:10 AM
  • Tiny
  • Docfixit
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That's why I asked test is started out on 10amp scale when first connect battery variuos relays and ECU are powered up. Then you set on milli scale this reads parasitic drain.5 milli is acceptable. Have recommended to many owners that leave car at airport for week or more to get a solar panel plugs into cig lighter will keep batt up.

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Monday, June 1st, 2009 AT 2:00 PM

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