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2000 Lexus RX 300 Repair Question


Topics covered: Battery, Fuse, Battery cable.
Mileage: No information provided.

Asked on May 30, 2009

2000 Lexus RX 300 RX300 Battery Drain

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.
Avatar Asked by wildron

Answer

Replied on May 30, 2009

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.

Tiny Answered by Docfixit (expert)
18,443 answers provided
Replied on May 31, 2009

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?

Tiny Response from wildron
2 questions asked
Replied on June 1, 2009

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.

Tiny Answered by Docfixit (expert)
18,443 answers provided