Lexus RX 400h Electrical/Lighting Questions

PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
edited April 2014 in Lexus
Discuss electrical and lighting issues here.


  • lexrexbluelexrexblue Member Posts: 38
    Lexus is currently installing a "security" kit to discourage theft of the HID lights. It involves installing dots, and a security bracket. It is free, but the kits are backordered so you need to make an appointment. Mine is currently for a week from now. They highly recommend it; especially if you park in the city. They even had problems with the lights stolen from their loaners.
  • krellukrellu Member Posts: 31
    I just spoke to a service advisor at lexus and he said that this kit is already installed in the 400h.Also said it is in stock for the rx330,in case anybody is interested.
  • lexrexbluelexrexblue Member Posts: 38
    It may be installed on the newer 400h, but not on mine. Mine was built in May.
  • krellukrellu Member Posts: 31
    Mine was built in march.
  • krellukrellu Member Posts: 31
    I just spoke to someone at customer service at lexus headquarters in Ca.
    800-255-3987.They said no rx400h had these kits installed.First they are working on the rx330 and then possibly the rx 400h.
  • lexrexbluelexrexblue Member Posts: 38
    I know that I have to drive to Queens soon and park the car. I don't want my 400h damaged so rather than waiting for Lexus to contact me, I called my dealer who is wonderful and they set up the appointment. They understood the problem because even their loaners have had the headlights stolen when parked in the city. I've decided that the slowest answers seem to come from the Lexus headquarters!
    I originally heard about the kit on another Lexus owners site so I just thought I'd share the info because nobody wants their car damaged or the headache or expense. In the suburbs we're relatively safe, but as soon as the car gets parked in a big city we're sitting ducks. I guess I was just fortunate the car was in a garage most of the time in Philly and lucky when it was parked on the streets for a relatively short time. I'm not planning to tempt fate too long!
  • foxgoosefoxgoose Member Posts: 2
    Got my new 400h on Friday in the UK and it's great - except that, while sitting in the car transferring my phonebook, loading CD's and playing with the ICE video system for an hour or two - the auxiliary battery went flat and wouldn't start the car.

    Rescue truck driver said its because it has a very small auxiliary battery for the size & complexity of the car.

    When I finally jump started it the engine ran for a few seconds and then cut out because the traction batteries were presumably OK.

    Seems weird that the car can be immobile because of a low aux battery when there's all that juice sitting in the traction batteries.

    Anybody know why the design doesn't allow for starting the engine from the main batteries via a voltage converter?

    Anybody else had aux battery problems?
  • wwestwwest Member Posts: 10,706
    It is my understanding that the 12 volt battery is (re)charged via a DC-DC down-converter from the ~270 volt hybrid battery. Since the down-converter replaces the more typical engine driven ~90-120 amp alternator it should at least have an equal level of capacity.

    So I would agree, it seems really odd that the down-converter, presumably rated at 50 amps minimum, wouldn't supply enough 12 volt "juice" to support the electronic needed to "signal" a need for an engine start.

    Actually what seems even more odd is that the 12 volt battery wasn't being continuously charged via the down-converter as you sat there "twiddling". No reason for that not to work even in the accessory position.

    Also makes me wonder if instead of calling for a "tow" you had simply placed the system in "run" for ten or fifteen minutes to let the downconverter recharge the 12 volt battery.
  • foxgoosefoxgoose Member Posts: 2
    OK - I've taken some measurements and I think I understand what's happening.

    When your sitting in the car "twiddling" with the ignition in the "accessory" or "on" position you can easily discharge the small battery quickly because there is no charging taking place.

    After you turn the key to "start" and the car enters "ready" mode there is a steady 2 - 3 amp trickle charge into the aux battery regardless of whether the engine starts or not. (When the engine starts I guess this goes up to conventional 50A or whatever charging rate but I haven't checked that yet.)

    You're probably right about waiting instead of calling the tow truck - but it would take a few hours at 3 Amps.

    Bottom line is - when twiddling stick to "ready" mode (but not in a closed garage in case the engine decides to fire up!).

    Does anybody know if there's a more technical user or workshop manual available for these cars - no one here seems to understand exactly how they work - including the dealers!
  • wwestwwest Member Posts: 10,706
    Yes, I bought the Toyota shop manuals for my 03 Prius right after buying it, fairly pricey though.

    There is also a Toyota internet site where the same info is available on a subscription basis.
  • lexi4lexi4 Member Posts: 8
    1st away for a week. Won't start. jump. ok. sat overnight week later won't start. dealer replaces aux. battery. 2 weeks later. sat overnight won't start. dealer replaces aux. battey. They have no idea.

    Does anyone have an idea / fix for this? no other gremlins. Can we use a larger battery?

  • engnrngengnrng Member Posts: 4
    Just joined the forum, as we are looking to buy a 400h, already own a Prius (2 years). Assuming 400h electrical system is wired same as the Prius, high voltage batteries are isolated from 12v system except when car is on. This is a critical safety feature for several reasons. The 12v battery is small because all it needs to do is boot the computers that control the ice and high voltage systems. When you turn the key to start, all you are doing is booting the computers. If your battery had enough juice to boot the computers, then leaving it in the ready state would charge the aux battery. Whenever I am fiddling with stuff on my Prius, like the nav system, I leave it on in the ready state. Every few minutes the ICE comes on for a few seconds to recharge the main batteries.
  • idingertidingert Member Posts: 1
    could anyone send me photos of the high voltage harness (Batterycable, U-V-W cables of generator / Motor..) and HV connectors of a lexus hybrid?
    Would be very great if you could help me!!


  • vegas1818vegas1818 Member Posts: 1
    I read your comment about the stolen HID lights. My friend's were taken twice in 6 months from his RX330. The dealer said there isn't anything to do, but you seem to have found a solution. I would appreciated your giving me any helpful ideas. I don't know how to get back to this forum since I've never used it. I found your reply through a search. Either please email me at or tell me how to find your answer here. Thanks!
  • myhybridmyhybrid Member Posts: 3
    I have had several episodes of battery failure recently. For my previous Lexus vehicles, and now my hybrid, I listen to the radio while using the accessory mode - and have never had a problem. In fact, even my daughter has used the Entertainment/DVD system for almost 20 minutes while the car was in accessory mode - and no problems. However, just this week we had problems with the battery. Three times the battery failed. Has anyone had such battery drainage when in Accessory mode operation. We are seeing this problem, during the bitter cold weather. Is the weather a problem? Thanks for your comments. Also, we have seen a drop in mileage. During the summer and fall, we had around 27-28 mpg. Now it is 20. Is anyone experiencing this?
  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAMember Posts: 9,372
    The extreme cold by itself reduces your battery's starting capacity. Add in the drain of extended use of Accessory mode, and you may wind up with a no start situation.

    Mileage for all vehicles drops during the winter months for a collection of reasons. People tend to warm up their cars, fuel formulations change, slippery road conditions... it all chops away at your mileage in the winter.
  • lexrexbluelexrexblue Member Posts: 38
    I have to confess that I haven't looked at this forum in a long time. I'm not sure what you're referring to. I had the Data Dots installed on my headlights (they put stronger brackets in, too) back when I wrote about it. They also put many stickers around the car. I've had no problems even in parking lots in Newark, NJ. I understand that the newer 400hs come in with them installed already, however, I don't know if the stickers are visible.
    Unrelated, you can purchase datadots from, too, but it isn't the same as the Lexus installation.
  • krellukrellu Member Posts: 31
    Have a grill guard installed.
  • myhybridmyhybrid Member Posts: 3
    Thanks for the insight on the battery. Again on the mileage question - is 19-22 a normal range for the winter? I used to get 27-29 easily during the past year. No matter how I cautious/concientious of a driver I am, just cannot get over 22.
  • supcommsupcomm Member Posts: 4
    The battery indicator show only 6 bars out of the 8 total as being charged. No matter how long I drive, I cant get the last 2 bars to show charged. Anyone know why this is or has this problem? Should I take it back to the dealer? Thanks.
  • herbrakherbrak Member Posts: 1
    To heat the car interior in the winter the ICE must heat the radiator coolant which is the source of the heat. So in the winter the ICE must run until that has happened. In the warm weather there is no need for that initial heating phase. So better mileage in the warm weather. Air conditioning is electric so the ICE does not need to be running.
    2006 400h - original model
  • wwestwwest Member Posts: 10,706
    In reality the way the climate control system works (reheat/remix airflow) in summertime "cooling" mode the engine coolant must also be up to nominal 180F temperature. And if Lexus has adopted, licensed, the Ford safety oriented hybrid techique patent then you will have less recharging via regen braking during colder weather.
  • removeumremoveum Member Posts: 3
    :shades: Ford is using Toyota's 1st generation hybrid system.
  • gladams1gladams1 Member Posts: 1
    In December I experienced a disabling failure of my 2007 400h. When I tried to start it, the cooling fan came on at high speed as well as a host of warning lights. The vehicle had to be towed to a Lexus dealer. They had never encountered this problem before. Eventually they determined that a relay had failed that prevented power getting to the hybrid system. Has anyone else experienced this problem? Were there any additional consequences? It has certainly shaken my faith in Lexus.

    Also, since the event occurred I have noticed that my hybrid battery no longer fully charges. The battery display never indicates more than 6 out of 8 bars. I start at the top of a long hill with 6 bars, and it still shows 6 bars at the bottom of the hill.
  • stevedebistevedebi LAMember Posts: 4,098
    "Ford is using Toyota's 1st generation hybrid system. "


    Ford independently developed their hybrid system, but the two technologies were very similar.

    Toyota and Ford SHARE patents between them, which means that Toyota is using Ford technology, and vice versa.

    There are also a number of hybrid patents Ford does not share with Toyota, which are being used in the FEH.
  • wwestwwest Member Posts: 10,706
    The way I read the news back at the time when the Prius was already in the market Ford was restrained by Toyota from marketing the Escape until a patent license agreement was made.

    So, no Ford patents were required for the original Prius but Ford REQUIRED Toyota patent licensing for the Escape.
  • stevedebistevedebi LAMember Posts: 4,098
    "So, no Ford patents were required for the original Prius but Ford REQUIRED Toyota patent licensing for the Escape. "

    My understanding is that they traded patent licenses, rather than any payments. Thus Toyota WANTED patents owned by Ford.

    Toyota made the Prius first, while Ford was concurrently developing the FEH, so of course they would go to Ford with discussions rather than vice versa.

    But in any case it is vastly different from Nissan (for example), which out-and-out licenses the Toyota HSD for its hybrids. Ford did the development, not copied the design.
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