My son purchased a 97 es300 awhile back and to make a long story short, the battery will need to be replaced soon. I know the lexus radio has a security code feature and we are not sure if it was ever set. Since the radio display is burned out, there’s no way to tell if a code is set or not.

Here’s my question, is there any way to change a battery while maintaining a charge to the car at all times so we don’t run the risk of having a dead radio. Even though the display is burned out, the radio & CD player works and we don’t want to go through the trouble of fixing the display just because of a security code.

Would appreciate any help on this
Thanks

 

change the battery with the car running.... thats what i was always told to do with any car...

 

simply start the car and with the engine running disconnect the positive lead first then the ground..put the new battery in reconnect the ground then the positive... all done

 

Thanks ... it never occurred to me to keep the car running

 

I would seriously recommend not to do that. You will almost certainly damage your charging system, and/or some very expensive electronic components if there is no load on the alternator/regulator.

If you have booster cables, you can keep them connected to the old battery as you change it out.

Just be careful not to short anything.

Phil

 

You should be able to tell if the radio's security system is set by checking the little red LED which is on the face of the radio. There is a small "key" symbol beside it. If this LED is flashing while the car is off, then the security system is set and the radio will lock up if the power is disconnected. If the LED is not lit and flashing when the car is off, then you should be good to go.

 

There are devices that use a 9 volt battery to save the settings, do a search for "12V Automotive Settings Keeper w/9V Battery". It uses a regular 9 volt battery to keep the electronic settings ie radio, while you change the battery. It costs less than 5 dollars, and is much safer than leaving the car running, or using jumpers.

 

FWIW, I had my battery removed for about an hour at one point, and I was not asked for a code. The radio presets also were intact, not sure how the security feature gets activated but it never did for me.

 

1. NEVER disconnect the battery from a running car, at least not a newer one with lots of computer controls that manage the engine. The alternator will lose the feedback from the battery, and it will go to full charge mode, which may send overvoltage into the system. This can damage sensitive electronics.

2. It has been my experience that those 9-volt memory saver devices don't work on Toyotas, because the lighter socket is a switched device via a big relay. The 9V that you feed into the lighter socket doesn't feed the coil side of the relay and it won't get energized, so the relay won't trip and send voltage to the radio. I tried it a few times and it never worked, then I looked at the wiring diagram and it made sense.

I assume the radio in your car is the same as the one I had in my '98. I had my battery out numerous times, and it never affected it.

 

[QUOTE=KLF;6151694]1. NEVER disconnect the battery from a running car, at least not a newer one with lots of computer controls that manage the engine. The alternator will lose the feedback from the battery, and it will go to full charge mode, which may send overvoltage into the system. This can damage sensitive electronics.



KLF is correct:

If you disconnect a battery cable while the car is running, the regulator sees total battery drain and immediately commands the alternator to run at maximum output. In effect, the alternator is now running wild. In this state, it can put out upwards of 40 volts. That’s enough voltage to fry your powertrain computer, your ABS computer, your radio, and every other computer in your car. It’s also enough to fry the guts of the alternator itself. Are you getting the idea here? That it's not a good idea to send the alternator into ‘full tilt?”

I've heard that there are some memory hold devices that plug into the OBD port that work.

 

wow i never knew that.... i guess u learn something everyday... i've changed many batteries that way. guess i was lucky...

 

Here is one of the products... you need an external battery source or another car nearby.


http://www.stockwiseauto.com/Schumac...source=froogle

 

This is not true, the regulator tries to maintain ~14 volts regardless. A battery acts like a giant capacitor to covert the diode filtered AC into DC. Without a battery, you are putting half wave AC into the car, not good for electronics. It is also very hard on the regulator circuit because there is no battery acting as a buffer, the regulator has to switch much faster, increasing heat dramatically.

 

why not just get the code when you are at the dealer sometime?