New to this forum. : )
I have the 2006 Rx400H and the battery died over a week ago. I had it towed to shop and the mechanic said he'd try to save the 12v battery. When he did get it to hold a charge he said the 'code' he gets is that the Hybrid control module needs to be replaced. Well, after getting the close to $2000.00 quote just for the module I decided to have the car towed back home (5 streets away). The battery was working when the tow company put it on the truck and happen to leave driver side window open to push and align with the tow truck.

So 5 minutes later it's lowered into my driveway and the man, being helpful, asked me to make sure the window was up. Well, the battery was dead again. He had a portable charger that he said was low and still hooked up and gave it enough power for me to turn on and put the window up.
I saw the dashboard lights and gps map momentarily with a 'system loading sign' where you normally see the map etc. Then he disconnected since the window was up and all went dead again. No warning lights nothing. I had to manually lock all the doors.

My question is... can I change this smaller battery myself and is it possible that the hybrid control module will reset on it's own? They told me it was very dangerous to work on high voltage cars and they have to hook it up to their machines to recalibrate etc.
I just watched 2 videos of the 51R 550 cca battery being replaced (DIY). It seems at the very least this could solve the issue and the control module is possibly fine.

My car had one other owner and in 3 years since I purchased, I've put 10K miles on always change oil, new tires and brake pads. Great car for me!

Really appreciate the support and suggestions in advance!

 

The 12v battery can be changed in the rx400h just like in any other vehicle. A weak or dead 12v battery can trigger all sorts of warnings, including those pointing to a fault in the main hybrid battery, even with no real fault. It is a side effect of certain modules not receiving enough voltage from the 12v battery.

 

Thank you for your quick answer!

I was wondering how the mechanic could test the control module and know for sure that it needed to be replaced. Even if he restored the battery temporarily, he mentioned he couldn't do the diagnostic since the module is what gives him the codes? Then he said don't worry the Hybrid battery is fine.

I think I will follow the video I found of how to correctly change the battery. They show having jumper cables connected to positive and negative when removing cables after bolts are loosened. I can't tell what the jumper cable connects too though. Could it be a portable battery charger or just cables?
https://www.carcarekiosk.com/video/2...eplace_battery

 

Some people recommend hooking up a 12V supply when changing a battery. This keeps all of your settings on your radio and prevents your ECUs from resetting. However, since your 12V battery is already completely dead, you do not need to do this. You never 'need' to do it anyway, but it may be useful for the prior reasons. In your case, just remove the old one, install the new one.

Remove the ground/negative cable before the positive, and when hooking up the new battery, connect the ground/negative AFTER the positive. This is because the ground/negative connects directly to the chassis, body, engine, etc, and any raw metal has a direct connection to the ground terminal of your battery. So lets say you put your wrench on the positive terminal bolt and swing the wrench down, accidentally bumping it into something metal under the hood, you will likely see some sparks if you have not removed the negative terminal first. Feel free to ask questions if you have them! Changing a battery is something anyone can do, just follow the steps and ask questions.

 

I am one of "those people" that absolutely recommends having backup 12V connected during battery replacement. Based on several owners at toyotanation that "simply did it" to end up with array of error codes on displays or, on one case, paying dealer and tow company to reset them, to the tune of over $500 expense.
Dead your battery might be but it likely still has residual charge. Electronics, it normally supports, also may still have residual charge. I'd say, it's up to you, to backup or not. Small inexpensive 12V source via cig lighter or power outlet won't hurt anything. May prevent something.
Btw, 12V does not operate windows. It is strictly electronics back up. ALL computers and some other crucial modules. This is why healthy 12V is so important.
I hope, your traction battery didn't discharge completely. That's tow to dealer and charging it, as you can't DIY charge traction battery.
Replace 12 v, worry about control module later.

 

if you are too worried to change your battery, just take it to an auto store and they'll change it for you in 5 minutes..

Costco/Sam's club is my first choice.
Autozone/Pep Boys/Advance are my second.

 

Yes, but he would have to have his vehicle towed there.

 

Oh.. booo.. AAA has on location change service with decent price.

... but he has to have AAA...

 

Thank you all for your advice. I'm female and yes I was emotional the day the car died in a large intersection. I do have AAA that towed to the nearest recommended shop. I can say that I was influenced by the statements when I was informed that I had to have the car worked on in an authorized hybrid shop because of the deadly electrical risks....etc.
So, as of now, I have removed the dead battery and will replace today (following the instructions from mnewxcv).
I'll update later how it goes and take pics of the dashboard. Hopefully, it will reset on it's own. I appreciate this forum.

Btw I also have respect for the fact that there are things that I should not touch due to high voltage. The communication I got was that I shouldn't change the 12v battery on my own....also AAA wasn't able to change out this battery either hmmm. I'm staying positive and moving forward in a better-guided direction.

 

1. Sorry for assuming you were male
2. The bright orange wires are the high voltage wires, so stay away from those and whatever those connect to, HOWEVER unless you go digging where you shouldn't, they do not pose a threat. What I mean is, you can still work on a hybrid vehicle when doing non-hybrid maintenance.
3. Congrats on getting the old battery out, you are 50% done with the job!

 

No problem assuming I was male lol....how could you know right?

I connected new battery (3yr warranty) positive side first. The car started and engine kicked on within a minute! Only had windows and radio to reset for module memory.
I'm leaving the a/c off and taking it to the A/C place, I was on my way to the day it died, to have freon with leak sealer added. I supposedly have a clogged evaporating tube because the passenger side floor soaked with water when the battery died. The mechanic said he could fix that for 200.00.

 

Nice, looks like no codes yet, hopefully it stays that way! As for the ac, does your ac work and blow cold? Water on the floor can be a clogged drain line, which really isn't a big problem, probably something you can do yourself if you are up to it. I've been having the same problem now that I'm using the ac more. Water occasionally drips on passenger floor, not much but it happens. Im sure there is a writeup somewhere but I can take some pictures once I address mine so you can see what you are getting into. 200 bucks to fix a clogged line seems excessive.

 

Thank you so much mnewxcv! The A/C blows warm like the air here. 5 months ago I had it checked and pep boys filled up the freon (or whatever it's called now) after they tested and said it was low. It worked great again. It only recently lost the cool air last month and we had record heat in high 90's feels like 112 temps. So, the leak seems small.

I was actually on my way to an A/C specialist shop when it died. AAA advised to have it towed to the shop where they went with the code that the computer control module was bad....same place that quoted 200.00 to fix a clog that I asked about after searching the internet while it sat there! Yes, excessive. I was counting on AAA to charge or replace my battery but they didn't do any of that. The driver saw the water on the floor and the next stop was the shop where it sat for a week. Thankfully, I paid only the diagnostic fee just under 90.00.

I've never had any water on the floor like that and I watched it back up and soak the floor mat when the battery died. So, maybe it isn't clogged?
I did find a video and I think my son could help out with that if it is the case. The thing is there shouldn't be any more water in the system right?
Here's the video and yes I giggled at the dramatic music.
PS: The A/C folks didn't want me to get there and then have to tow it again if something else was wrong that they don't handle. Wish I had taken that chance; went to them and just got a new battery. Learned some things and moving forward. They are my first call when they open.

 

Not sure I'm entirely following your post. If the wet carpet only happened the one time the vehicle shut down because of the battery, I wouldn't worry about it yet. Perhaps there is an electrically actuated drain valve? I honestly don't know. But again, that was a unique situation.

I think the general consensus is that Lexus put too small a battery under the hood (not the hybrid battery). The evidence people use is the 450h got a bigger one. Its good to keep an eye on them, and change them out with a new one at the first sign of it getting weak. I only seem to get a couple years out of mine. The 400h can do some weird things as that battery goes out.

On that note, I'd try your a/c again now that you have a new battery. I doubt it will work, but it doesn't hurt. These things blow cold quick, so you'll know right away...

 

Some good points here. The ac runs on high voltage, so there could be a connection. Also, blend door actuators are not an uncommon problem.