It pain because I love the 400h and I have never had anything negative to say about it. In fact, it has been far more reliable than our RX300. However, tonight it let me down.

I needed to jump my Subaru so I figured the 400h would be fine vehicle to do so. Note that the 400h had a dead battery that gave us a problem for a few days a couple months ago. Given that this battery only had 50k miles on it we didn't replace it nor did we have it charged at a pepboys, autozone, etc. Everything has been okay since then.

It jumped my car fine. I had the 400h running while I did it. I went to start it a few hours later and the lights came on as usual, but no "ready" light. After that I only got a check engine light with the ocasional hazard light. The rear hatch wouldnt open. However, the engine fan did come on and so did the interior lights suggesting to me that the battery is okay. I cannot figure out what is wrong. And I am thankful that we are at home and not stranded somewhere. So I am wondering if anyone has experienced this problem. It is like we are locked out of the whole system. No radio, headlights, engine.

I recall reading something about having to do a reset at the dealer on the early 400hs if your battery goes dead. We did not do this. I also recall reading that not performing this procedure affects fuel economy. I rarely drive this vehicle, but I checked it this past week. 23 MPG is an all time low, even for winter, which I thought was the initial explanation. Now I am not so sure. Anyone have info. on this?

 

The fact that you had battery problems a while ago, and these problems started after you boosted another vehicle really leads me to believe that this is a 12 volt battery problem. Why don't you bite the bullet and have the battery tested and/or replaced. Alternatively, I guess you could use one of your other vehicles to boost the RX. If it starts when boosted, then you know it's the 12 volt battery causing the trouble.

What year is your 400h. The ISC learning procedure needs to be performed on 2006 models (per the TSB - don't know if it applies to later models since the TSB came out in 2006) if the battery is removed or run down below 7 volts or so.

 

Yeah. We jump started it this morning and it started. Looks like a new battery is in order. However, the battery itself says that it is fine.

Our 400h is a 2007. And I haven't seen any info. on the TSB applying to models later than 2006. But I am going to call the dealer and ask anyway. Couldn't hurt and like I said, that would explain why the mileage has been declining.

 

Had the same thing on my 12 volt battery. The eye thing showed blue (indicating all OK) and the car started fine, but if I left something as simple as a door open for 5 minutes, the READY light wouldn't come on, power hatch would beep and beep but not move etc.

Had the battery tested, and it showed CCA of only 150-200 or something, when it should be 450. Granted CCA are not needed on our vehicles, but it did indicate something amiss with the battery (bad cell probably).

Anyway, threw in a new battery and it's been great ever since.

 

throw in a new battery.. OEM battery in this car doesn't last as long...

 

Yup it's your battery problem I had this too when I only had like 20k miles on the odometer, purchased the car brand new too....

 

That's what I wanted to know. I figure we got 60k out of the battery, which is decent. I have to schedule a service for it soon, in which I will inquire about the TSB. My dad drove it yesterday and he said that the engine was definately running a varied speed while idling so it sounds like the ISC procedure may be pertinent to the '07s as well.

 

Its simple, replace the battery the standard battery is very small because of it not being used to start the car. However for some reason when the battery is low at all it will not start even though the hybrid battery has plenty of juice.

 

Down to about 20.9 MPG Avg. and falling. My mom called her dealer about the TSB regarding idle speed but they had never heard of it. I called another dealer, explained my plight and that we had replaced the 12 Volt battery and they told me that they would only perform this procedure when replacing the 12 Volt battery. Thus, I reiterated that I did replace the 12 Volt their response was to run diagnostics, but they agreed that 20 MPG and dropping is unsual. Not sure what to do here.

 

Got a hold of our usual dealer and explained the situation. They said that they one case in which the inverter had to be replaced after changing of the 12 Volt battery. They would like to run diagnostics on it as well. My parents are supposed to take a 1500 mile trip in this vehicle, leaving Saturday and the dealer agreed with me that they should not take it without it being looked at.

Unusual behavior this is for this car, but 2007 was only the second MY so I can understand all of the kinks not being worked out.

 

Apparently the 12 Volt battery had a bad cell. The engine was working hard to charge it. Thus Lexus actually replaced the battery under warranty. That's good to know. Still waiting to get it back from the dealer to see if this is the true fix. But it makes alot of sense.

 

Why don't you just print out a copy of the ISC learning procedure TSB and show it to the dummies? You can find it here..

http://us.lexusownersclub.com/forums...howtopic=58929

It's item #8 in my post. The TSB does say 2006, but maybe it applies to 2007 as well (maybe it states 2006 because it was issued in 2006 and the 2007 wasn't being made?) Either way, once the dealer has it, they can call the corporate tech line and ask if it applies to the 2007.

 

I guess it makes sense. Although there is no alternator - the 12 volt is charged via the traction battery. So I suppose that if the 'traction battery' was working hard to charge the 12 volt, then it would run down sooner/more often, and thus the ICE would have to run to charge the traction battery back up.

I don't know what effect a bad cell would have on the system...would it cause the computer to 'think' that the 12volt battery was in a low state and send more charge it's way, leading to the above situation? I guess you'll know when you get the car back.

 

24 MPG and climbing.

 

I drove thw 400h last night and it is running normally again. Very nice. I did a few burst of acceleration and still managed to go from 24.2 MPG to 24.9 by the end of my short trip. I forgot how nice is that you can run on electric alone on some of the roads around me, one in particular is 30 MPH and flat. Ideal for using less fuel.

I would love to try the 450h, however as Lexus expand I'd like to see some 350hs more fuel economy oriented. My buddy's parents have the GS 300 AWD with the DI V6 and he reports 30 MPG Hwy. I'm thinking that this would be a fine engine to pair with HSD.