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Ls400 Potential Problems


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I ran across this former thread on this site. It is one of my worries about parking any car in a garage attached to a house. I don't trust electric things much at all, and I have an FCC license that will allow me to work on aircraft radios so I know a bit about the subject.

Some years back Ford trucks were catching fire due to the switch located on the master cylinder that was to disengage the cruise control. They would leak and short out causing the feed wire to get hot and thus cause a fire. It just so happened that it was not a fused wire, so Ford had a big recall and the fix was done to the wrong wire so the problem continued, and they finally got it all sorted out and fused the correct wire.

Most people think all electric current is nonexistent once the ignition switch is turned off. Not the case.

There is memory keep alive current for most of the ECU's in the car as well as the radio, most of the lighting circuits, and power seats, door locks, alarm system, and I think the charging system.

And before you poo poo me look at this.


I'll continue later

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A study of wiring diagrams shows the alternator has power all the time to both the regulator and the rectifier diodes. If something breaks down or has water or oil enter where it shouldn't it could cause a short, kind of like the Ford cruise control switch, hot wires can start fires and even just a small current can too read the 9 volt battery article. A 9 volt battery is not going to put out the amps that some of the fuses in cars will allow. I'm not picking on Lexus, since I do have a few of them. I'm just saying it is possible to have a fire start from a small current or large, and its something to be aware of especially when parking your car in your house. Yeah you loose some radio channels, seat and mirror positions etc. but its better than the alternative, its a good idea to disconnect the battery on any car or truck when inside less you have a good sprinkler system.

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Radio presets, seat memory, and mirror positions aren't the only thing you lose when a battery is fully disconnected from the car. Once the car is connected back to power, the computer wakes up and has to relearn everything from the idle speed to when the car shifts. It's programmed, and it's in there where it can't be erased just by taking out power, but all the things the computer has learned get lost. As you drive, the computer continuously modifies its programming as far as injector pulse width, timing, and transmission pressures to provide you with a smooth comfortable drive. When you disconnect the battery, you lose this and the car has to start over. For the next few miles to the next few hours to the next few days as you drive, it has to fill in the blanks with a very small representative of your driving habits.

Why do you think products like memory savers exist? Why do you think the 9 volt battery thread exists? If you have to force your computer to relearn everything after say, an injector replacement, or a transmission rebuild, that's one thing. You want it to relearn all those parameters. But to make your car relearn everything from scratch every time you want to drive it? That's like taking a PE class at your local community college before joining a few friends for some hoops down at the park.

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Well yeah electricity is dangerous. People were killed by it long before it was even invented and you can't say that for many things. I once had a student in an electronics class that did the old "test the 9V battery by touching it tongue" thing. Unfortunately the kid had braces. At that point he learned exactly what a direct short was.

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