debmalya

Thanks for your replies. I beleive the RX400h uses the Toyota 3MZ-FE engine http://en.wikipedia.org/wiki/Toyota_MZ_engine. I was not able to find out if this engine is interference or free running. I vaguely remember reading some where that Toyota's policy is to use chains in interference engines and belts/chains in free running engines. I now know that this engine uses a belt and recommended replacement is at 90000 miles or 96 months, both far in my case. Thanks for your inputs.

Hello folks What type of engine does the RX400h have - is it an interference engine or a free running engine? Also, does it have a timing belt or chain?

Another thing to note is, the replacement battery that Lexus provided under warranty is slightly bigger than the original one. Thus it does not sit within the battery tray, rather it sits on top of the flange of the tray. I noticed this and clarified it with the mechanic at the dealer. He said that's how the newer batteries are, but the clamp will hold it in place. Not to mention, the new battery has not moved from the tray in 8 months. But it still seems awkward that the replacement battery has a different footprint than the factory battery. The battery problem I beleive is not uncommon. My car would not turn "Ready" and would indicate "Shift to P when starting" even though it was already in "P"! I had to take a picture and show the dealer as they were not able to reproduce it. If left for long, the battery would most times work. Lexus dealer couldnt diagnose the problem, kept my car for 1 week (and offered me a standby vehicle which I declined) but couldn't figure the cause. Then I suggested them to perform a load test on the battery and they found out the "weakened/dead" cell. Touch wood its been working since.

Agreed! My RX400h (auxillary) battery died [one dead cell] under warranty (luckily) and the car was towed to the dealer and replaced at Lexus' cost. The battery tends to deplete easily if the car is not used for a few days. I believe the manual documents that the car be driven for few (?) miles every 2 days. I believe that the (aux.) battery is only charged when the gasoline motor is running. Since the gasoline motor is not engaged at all times, maybe the battery is not charged the same way it is done in a conventional gasoline vehicle. But my understanding maybe flawed about this. But in any case, Lexus should have designed this better and reliably.

I have had other problems with my RX, where it would refuse to start and kept displaying shift to "P" when starting even though the car was in park. And then would start (ready) all of a sudden. I had to call Lexus road side assitance twice and cancel the call because after a 30 min wait or more the car became driveable again. I took it to the dealer every time and they checked the car thoroughly, kept it for few days, and came back negative. Every time they said, "we could not find any problems with the vehicle or any fault codes. Never have we heard of such a problem either." And then when it happened the next time I luckily had my camera, so I took a full video footage of the display, the shifter position and my attempts to start it etc. and played it to the service guys. They again kept the car and kept telling me "we believe you but we can't find the problem". Then I suggested them to test the auxillary battery (12V) and voila, it had a dead cell! They replaced it under warranty, but fitted it with a bigger battery whcih does not fit the battery plate. The new batteries have a slighlty bigger form factor. Honestly I have never owend any of those vehicles you mentioned and therefore can not comment. I guess you have valid reasons to say so. But, if at all, poor design and quality of other makes will not make Toyotas any better, will it? A sampling rate of 20 minutes on a tire pressure monitoring system simply tells me that whoever engineer conceived or designed it lacks common sense, not just engineering skills, won't you agree?

Ok ... #1 thanks for the information. to answer your question, Yes, the flat occured while driving. The tire was inflated when I started. I noticed the flat within a few minutes (hopefully) when it must have happened and immediately pulled over. It was completely deflated though, not just partially deflated. In any case, I believe I noticed the problem and acted in less than 20 mins. so if what you are saying "requires at least 20 minutes of consecutive readouts" is correct then I have my answer - thank you. If the Lexus engineers conceived a 20 min latency in tire pressure comaprisons then it is alarming to me that people with such common sense are involved in designing Toyota cars. No wonder the woes!

Update: just received a call from the service manager explaining how the "crappy" Lexus system works! It utilizes wheel speed difference to sense a deflation condition. I don't understand how it differentiates between the conditions turn, wheel lock up during braking, or defaltion, in either of these cases the wheel speeds will vary. Per the manager he also feels the early Lexus design is poor, inadequate and unrelaible at best. He claims they improved it in the later models that are equipped with valve stem sensors.

I have the 2006 RX400h. Yesterday the front passenger (RH) side tire went flat on a local street at slow speed. I relaized the problem when I felt the car drag and immediately pulled over to check - confirmd it was a flat. But I was surprised that there was no TPMS warning light indicating the flat! I was expecting one! I contacted the dealer's service deparment and one service advisor explained that the 2006 models are equipped with some "indirect TPMS" that may not indicate a tire depressurization if the tire is rotating fast enough - if this is true I am scared. I guess you are more vulnerable to a loss of vehicle control if a tire fails at a higher speed. Anyways, in my case the car was going quite slow, maybe 20-30 MpH or so. And the light never came up even after I brought the car to a halt. I am not sure if what the service advisor is telling me is right. Would appreciate if any of you guys can point me to something more rational. Thanks guys.

Thanks a ton to you. I did my oil change and your pictures made it very easy.