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100 VX electrical problem

Gary Stockton

Super Moderator
Sep 10, 2012
Country Flag
Hi all,

Jos from LCCSA has asked me to post this:

I hope you can help: I have Barries' L/C in my workshop and it is draining the main batteries within a few days. There is a 270mA drain which is causing this and I am convinced it is the backup battery of the TVSS (Toyota Vehicle Security System) which has died. The only problem is I don't know where it is located. Looking on the web site seems to confirm this diagnosis, but I cannot find any post where anyone has identified the battery's location.

Would you be so kind as to put up a post requesting this info?

Vehicle is 1999 LandCruiser 100VX 50th Anniversary Edition Turbo Diesel UK Spec (was imported into SA by previous owner)

There is a similar post elsewhere about this:
My 4.7 VX Amazon is draining the battery in a couple of days if I don't use it. I just had to fit a new 720A battery because 2 of the cells in my prevfious one had died. I measured the current drain with everything off and something was pulling 270mA. I went through the fuses one by one, pulling them until the drain reduced. There is a fuse in the Left hand side front of the car (I have a right hand drive) marked as ECU-B. Once I pulled this the current drain dropped to 70mA.

Does anybody know what ECU-B is?
Is this an easy part to replace?
Does anyone know approximate costs (in UK pounds would be helpful) or do I leave it and live with replacing a battery every 12 months as a cheaper alternative?

Cause remained unknown I think?
I don't know where the back up battery is. The TVSS box is under the cente console, forwards of the gear selector, a little black box that says TVSS on it and has a sensitivity dial. Not sure that box does anything more than being a pressure wave sensor though. Has he checked the drain is through the ECU B fuse as per the second part of the post? The twin battery trucks can have a high current drain between the two batteries when one of them starts going bad.
Gary in this manual, , there is an entire section on the theft deterrent system and it shows the Theft Deterrent ECU sits behind the glovebox, see page DI-634. The Theft deterrent ECU power source schematic is on page DI-640, but I only see the main battery, no back up battery. If you run a search on "ECU-B" it pops up quite a number of times and on various circuits.
Thanks for all the help. It turns out the 270mA drain is normal with the vehicle unlocked. Once locked the drain drops to about 100mA which is acceptable.

PS, I found the backup battery for the TVSS but I'm not sure I should post the detail in the open. Anyone who needs this info is welcome to contact me.

Thanks again :clap: