tman9999

2003 RX300, with 110,000 miles or so. We've owned for a few years, since
90k or so. No issues, other than battery dying if we let it sit for several days
without driving it. We bought a battery quick disconnect that mounts right on
the battery terminal to fight the passive drain issue, and that has worked fine
for last 2-3 years or so.

Recently we saw the VSC/Check Engine light come on intermittently. Since
we disconnect the battery and leave it that way until next time we drive car,
that seems to have lessened.

But now a new issue has emerged: if we leave the car sit overnight without
disconnecting the battery, the next day the entire electrical system is down.
No remote locks, no interior lights after manually unlocking/opening the door,
no dash lights with the key in the ignition, and no starting.

Oddly, this is "fixed" by simply opening the hood ('bonnet'), disconnecting the
battery with the quick disconnect, and then reconnecting it. Lights come on,
ignition key warning bell sounds, car starts right up.

So why would cycling the battery connection 'fix' this issue? What would
someone do if they didn't have the quick disconnect? Who'd a thunk that
would work? It appears like a completely dead battery, but that's actually not
the case.

I'm reluctant to take it to a dealer - sounds like lots of bad experiences getting
charged to replace all sorts of stuff that may or may not address the issue.

Thanks for any ideas.

salimshah

First welcome to Club Lexus.

Please look up the discussion on parasitic draw in RX. I think that needs to be investigated/traced etc. Check if any light remains on after you shut the RX. You should start by alternator and then work with fuses to figure out what is drawing un-necessary current.

Brand new battery should be able to sustain 3 weeks of no use.

Realistically, the problem has to be debugged by Lexus, independent mechanic or by DIY. Dealership prices are the highest per hour, but they will be able to diagnose in shortest time. [at least that is the hope]. They have the edge of experience on their side. I trust my local dealership and since I do DIY, I interact with parts. I check with them and if their price is higher I go else where.

RX go through 2 levels of reset. One is when you turn off the RX and then turn it on. I call it half reset. The other is the hard reset which happens when you disconnect the battery for about 20 mins [can be much shorter .. but essentially one waits for all stored settings to go away in the ECU].

You have battery drain problem as well as CEL, which is triggered by any of the sensors [please see Having problems, start here sticky thread]. With the disconnect and reconnect of the battery you are most likely wiping the error code every time.

Salim

thaeleelyr

I had a marker light that was damaged internally. I found it after the bulb kept blowing. When I took it apart the connector was burned. Replacing that mostly fixed the drain overnight I was having.

However, I still have issues with older batteries (over 1.5 years) with a drain after a few days. I also notice some issues indicating that the alternator may be going, although it still tests good. Drcoffee just posted a good DIY on changing the battery ground wire. I never thought about corrosion under the battery cable sheath and I'm going to try that to see if it gets rid of the little nagging drain. Corrosion on cables will also put a small draw on batteries. I don't know if this is your issue, but you may want to check those cables.

I've never had any luck with any garage diagnosing things that are as difficult to find as electrical drains, but if you have a good mechanic you may have better luck.

Have you tested the battery after you let it sit overnight, before you disconnect it? I have an older RX: does your model include a feature that turns off the electrical system should the battery get to a certain level. By this I mean, if you accidentally left a light on, maybe the computer shuts everything down to preserve the battery. Did you change your routine to where you notice it now? You might want to experiment for a few days: leave the battery connected and start it every day. Check the battery level every day to see if it degrades over time.

The danger of disconnecting the battery so much is that it wipes out the CEL trouble codes. If you have one pending without the light coming on, it'll get wiped. It can take 15 miles of driving before a code is generated, especially after a hard reset from disconnecting the battery for so long. I don't think you wipe the trouble codes if you just disconnect/reconnect the battery as there is residual charge in the system. It may be worth your time to do the above daily experiment just to see if you get any codes. Advanced Auto will read your trouble codes for free.

Good luck and please let us know when you find the solution as it may help others diagnose their issues.

Drcoffee

http://my.is/forums/f221/diy-chargin...attery-426000/

DIY DIAGNOSING ELECTRICAL SYSTEM

You will need a multimeter which cost about $12 at hardware stores

tman9999

Thanks, all, for your input (and the welcome to this forum - love it!).

I think we may have traced the problem to - are you ready for it? - a loose battery cable connection on the negative terminal. DOH!

I put my voltmeter on the battery and I was showing a solid 12.8 volts at rest, and 14.2v with engine running, so I'm hoping that's solved the issue. Obviously will continue to monitor, particularly if it starts throwing VSC/CEL lights again. Now I know what to do: take it over my local O'reilly's and they'll put it on a scanalyzer and tell me what codes it's throwing.

Anyway, great forum - thanks, again, for your help.

salimshah

Well .. bad ground can explain poor charging and poor starts. Drain offs based on days of no use is hard to understand .. unless the draw from starting never got compensated with the charging.

Let us know if everything is back to normal and what codes your RX is throwing.

Salim