wil4713

Hi all,

Newly registered on here, but I have been reading lots before I posted. Have already learned lots--thanks!

My mom has a 2004 RX330, which I'm currently driving to help her figure out the problem. To summarize, she has had a parasitic battery drain for the past year or so. The car was owned before by an elderly family member and only has 64k on it. Never wrecked, flooded, etc. In great shape except for the typical cracking dash and now her battery problems.

What my mom verified to me:
1) being unable to crank the car if she does not drive it for 2-3 days. With regular driving, it's not an issue.
2) New battery approx 9 months ago after issue began. Battery has since checked out by mechanic recently.
3) Alternator also tested ok
4) My mom has been driving the car without the DCC short fuse in (so couldn't use remote locks, radio) for the past several months. With the DCC short fuse removed, she does not have any issues with being stranded, dead battery.

She'd like to use those convenience features, however, so I'm trying to figure out where her drain is coming from. I have tested current draw on two nights so far this week. Using a multimeter (on the 10A DC setting) clamped to the negative terminal and the negative lead on the battery, it looks like she has an intermittent draw.

First night of testing:
Clamped multimeter as above. 590mA draw, decreasing to 250mA after a few seconds and remaining there. Draw decreases to zero if I pulled the DCC short fuse or the ECU-B fuse. Didn't have time to test further.

Last night:
Multimeter as above. 590mA draw, decreasing to 250mA after a few seconds and remaining there. I pulled the Door No. 2 fuse (Multiplex Communication Center), and the current dropped to zero. After replacement of that fuse, the draw pattern changed to: Initially 590mA briefly, then 250mA for 2 minutes, then 30mA and remaining there. I checked this pattern twice and could not replicate the 250mA current staying on indefinitely.

I stopped testing at that point--30mA seems like a probably appropriate current draw and unlikely to drain the battery so quickly.

In terms of other electrical issues, so far I have only uncovered problems with the windows and back hatch. I learned about resetting the windows after a dead battery already (thanks, CL!) yet I am still having trouble with that. Once, having reset the windows after pulling the negative lead off, I could make all windows function correctly (auto up/down from master switch as well as door switches) except the passenger front window (auto up/down from door switch worked, but not master). Currently, after the most recent reset, all windows work (auto up/down) from their own switch, but the master switch will not work to control any other windows. The back hatch I have not tested much, but noticed it works infrequently.


So I guess my questions are:
1) Any recommendations on where to go from here?
2) From reading about some other folks with parasitic draws, it seems like probably my window problem and the drain are related. Does that seem correct?
3) I see that there are multiplex units available used and feel comfortably replacing them, but I'm not certain which multiplex unit to replace and/or where the "Door No. 2" multiplex unit is located (there seem to be multiple units when I search online for them).
4) I also feel comfortable swapping out my master window switch, but again, hesitant to do that as it seems variable and possible connected to other issues

Thank you for reading and for all of the help!

Margate330

Hi friend,

You probably haven't gotten any replies since the problem seems complex and intermittent and adding an intermittent trunk to it makes it harder and could suggest Body Ecu/multiplex issues, etc and lead the diagnostic down the wrong direction without doing the easier stuff first.

Without taking the trunk into acount and focusing on fixing the "windows not working properly from Driver's Side Master Switch" may lead to solving the parasitic draw problem too as a added bonus.

As you probably already know the Driver Side Master Switch is also a Muliplex Module and if it is failing it can keep the Body Ecu "alive" either intermittently or all the time.

Any of the other switchs/modules in the other doors or the rest of the car for that matter can do this too but you seem to be having problems with the Driver's Side Master from your description above.

If you can prove a failure at the Master Switch it could be a great place to start.

spinellib

Yeah, an intermittent draw is a difficult mystery.
An example would be a failing Rear Wiper trying to find "home" every once in a while.
Unless your eyes are glued to the multimeter for 2 hours, you might miss the 3-second "event" when the rear wiper circuit activates.

Brucecav

I have the exact same problem with my 2004 Lexus RX 330. However, all of my window switches seem to be working fine. I have resorted to pulling out the ECU B fuse when I set the car overnight. It's a pain in the butt but I've tried everything else. It's very much the same thing as yours, if the car sits 2 to 3 days, I have no battery left to start it. The alternator is brand-new and the battery is fairly new as well. I have confirmed the parasitic draw of an equivalent amount that you had. Someone said to try replacing the multiplex communication box that is behind the rear seat on the driver side. I really haven't gotten motivated to open up the side panel and look for it. I have also had intermittent problems with the rear hatch.
I think whatever we have going on is very similar. Please keep me posted if you find the fix.
Bruce

wil4713

Hey guys, thanks for your replies. I must not have had the alerts turned on--just seeing the last two. Some updates:

I replaced the driver's side master switch as suggested. No change.
I also replaced the rear multiplex box (under the driver's side rear three-quarter-panel). I realized that the first part I bought was the wrong part number (from a later model), so bought another of the correct year. Neither has solved my issues. Haven't rechecked the draws on the multimeter, but still having problems with starting if I leave the car idle for more than a day.

Additionally, I've also noticed that (sometimes) my master switch still operates even after the keys have been removed. Not every time, but sometimes the switch works even 30 minutes after turning the car off, opening the door, etc. Switch feels warm, as well--might be the lights, I suppose.

Also, very intermittently my driver's window has started to have problems rolling up or down. Has only happened a few times so far, but the window will work normally going down, e.g., then won't come back up. Once it's started this episode, the window has trouble going up or down. E.g. if I have the window down halfway, then when I move the switch up or down there's a click (sounds like making contact) and a brief movement of the window up or down, whichever way I'm pressing. I have read issues about a failing motor, where the problem is mostly that the motor is not strong enough to push the window up. My problem happens going down or up. Can happen if I have just begun to use the windows or after repeating up/down cycles.

I found one other thread where someone solved a drain problem here: https://www.clublexus.com/forums/rx-...h-car-off.html
This poster, Savnout, had the same switch-staying-on issue and replaced the control module that's apparently part of the fuse box. Sounds like he had other electrical issues, too, which I don't have. I'm not sure what other next steps to take, so that's next on the list unless other suggestions.

Thanks for reading!

Margate330

Hi friend,

If it looks like this it's the body ECU, link: https://www.clublexus.com/forums/rx-...with-pics.html

It's the body's multiplex brain and interior fuse box all in one.
I was hoping with the new driver switch you would be done but the body ecu can cause random issues and it looks like you already did the easy stuff trying a new master door switch.

I got a used body ECU on ebay for $50 to keep on the shelf just in case I ever had a parasitic draw since it would be so much easier with a known good spare to swap before pulling the interior out looking for a corroded connector, water leaking on something, or worse unplugging every component and module in the car chasing it down. lol

wil4713

Thanks again for the help. I got the body ECu in the mail last week and installed it tonight. Not too bad to put in. I am a little bit pessimistic that I fixed problem, however. Still having window switch issues after the replacement. The master switch works on the driver door but there’s not work on any of the other windows. Windows have been re-initialized and each switch works on its own door. When I remove the short pin and crank the car, master switch controls all of the windows normally. So far I have not seen the switch stay on w car off, which I had before, but we’ll see.

I didn’t do a draw test yet, though I have replaced the short pin, so if the draw is similar to before, I imagine I’ll find out soon.

I don’t care as much about the windows not working, but I feel the most likely thing is at the window issue and the parasitic draw are related. Obviously since I got an eBay part, there is a possibility that I got a bad unit. Beyond trying another used unit, any other diagnostic possibilities that I should be considering?

Thank you again for your help!

Margate330

Hi friends, treating this as a case study and just putting this out there. Any errors found plz let me know so I can fix them and if anyone has more info plz share. TY

"The master switch works on the driver door but there’s not work on any of the other windows.": With the ignition key inserted and turned on, whether the car is running or not running, windows should work remotely using the driver side switches. Also, with no ignition key my windows do not roll up or down remotely using the driver side window switches. Lexus RX330

"Windows have been re-initialized and each switch works on its own door. ": Each door switch controls it's own window locally without using the Body ECU except for controlling windows remotely with driver side window switches, Techstream, or using the key in the door. With the keys out of the ignition, the windows should roll down remotely using the driver side key lock with the key turned and held in CW rotation.

"When I remove the short pin and crank the car, master switch controls all of the windows normally.": This is normal- removing the "Short Pin" unhooks the Body ECU's voltage when the ignition is OFF so it will disable the radio, info, dash cluster, etc, etc for many features that can run with the key out of the ignition. Cranking the car or turning the ignition switch ON routes the IGN 1 fuse to power the Body ECU. So, the Body ECU uses the ECU-B fuse with no keys in ignition and it uses IGN 1 fuse when ignition is on.



From a bench test I did a few months ago this is what I came up with.

wil4713

Thanks again for all of the help. What is the expected behavior with the key on when the short pin is removed? When I have that pin removed, I lose function such as the radio, review camera, and I have multiple lights on the dash such as the VSC light, etc. I guess I assumed this was also normal behavior with the short fuse removed. Is this normal behavior, Or does the short pin fuse only affect behavior with the ignition off?

I am thinking that perhaps I got a bad body ECU Off of eBay since my problems persist, and I’m not sure how to track down other possibilities. I don’t have techstream. I’ve been looking at the wiring diagrams, but I’m not sure that has helped me much more. Any other thoughts or hints?

thank you!

Margate330

Chances are your Body ECU is ok because there is so much going thru the Body ECU that the likelyhood of the exact same symptoms with the spare unit is possible but highly unlikely.
From your description this sounds normal since pulling DCC "Short Pin" fuse cuts power to several things- see below.
Some features will overlap because pulling the "Short Pin" might kill the Radio, etc because it kills the power to it. Windows are powered by their own fuses taking another path so when key is on the Body ECU goes into a different mode and gets power from IGN fuse so that's why you can control windows with keys on.

PS- Simple Test, with the keys out of the ignition can you roll your windows down using the key in the driver's door as mentioned above???


You will lose all these things when pulling the DCC aka "Short Pin". Things that still work have a 2nd path or mode by being powered by a 2nd fuse like the Body ECU.

jbtvt

Move your meter in series down the circuit until you isolate where the draw is coming from. For example between the positive lead into body ecu, and the ecu itself, then between each window switch and ecu, etc. Chances of 2 bad ecus are very slim, as mentioned. No need to throw parts at it, just follow the current and find the short circuit or bad component.

jbtvt

Attached files are power window and door lock diagrams, and location of your ECUs and relays

matts6887

I too am having issues with my windows. Initally when i went to my indy shop down the street; it was diagnosed as the master window switch becuase my front right and rear windows will not go up and down from the master controls on the drivers side. I replaced the master control panel yesterday but that did nothing to fix the issue of the right front and rear windows not wanting to go up and down from the drivers master switches. its driving me crazy as if im not already there which i am!

Margate330

Here are some simple tests to gather info and if anyone has more ideas plz feel free to add.

>> Before proceeding the windows should be initialized following the standard window initialization procedure.
>> "Child Lock" button on the driver side master switch should not be activated.
>> Battery voltage should be confirmed to be within spec.
>> ADD- if driver side window switch was already replaced, plz confirm that it is good- see https://www.clublexus.com/forums/rx-...8-windows.html

Step #1) With the engine running or the ignition switched to "On": Can all the windows be rolled down from the driver side master switch? if not, plz describe with details
Step #2) With the keys out of the ignition and car is not running: Can all the windows be rolled down from the driver's door lock using the key? if not, plz describe with details


Since one bad window switch can keep the others from working(mpx wires), here is a simple test.
1) Unplug all window switches except for the driver's window switch.
2) Plug in any window switch and do the test above again and then unplug the switch when done.
3) Repeat for remaining window switches plugging in one at a time to find a bad window switch.

Good luck!