2006 Rx400h - Tpms - No Warning On Flat!

[debmalya]

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.

[debmalya]

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.

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.

[cduluk]

Did the flat occur "while" driving? Or do you suspect it was flat before your trip? How long were you driving before you noticed it was flat?

The car requires at least 20 minutes of consecutive readouts before notifying you with a warning light. If your tire is flat, only after 20 minutes of driving in D will the light come on...

[debmalya]

Did the flat occur "while" driving? Or do you suspect it was flat before your trip? How long were you driving before you noticed it was flat?

The car requires at least 20 minutes of consecutive readouts before notifying you with a warning light. If your tire is flat, only after 20 minutes of driving in D will the light come on...

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!

[RX400h]

Well I wouldn't trade my RX400h for any other SUV. If this is the biggest problem you've had, you, like the hundreds of thousands of other RX owners, are very fortunate to have a Lexus and not an Audi, Mercedes, Porsche, or BMW SUV!

[debmalya]

Well I wouldn't trade my RX400h for any other SUV. If this is the biggest problem you've had, you, like the hundreds of thousands of other RX owners, are very fortunate to have a Lexus and not an Audi, Mercedes, Porsche, or BMW SUV!

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?

[lemon]

There is no TPMS on the 2006 400h period. Not even an 'indirect' system as some moron at the dealership mentioned. I'm not sure about the 330.

[lemon]

Did the flat occur "while" driving? Or do you suspect it was flat before your trip? How long were you driving before you noticed it was flat?

The car requires at least 20 minutes of consecutive readouts before notifying you with a warning light. If your tire is flat, only after 20 minutes of driving in D will the light come on...

Where are you getting this information from? That's a daft system - I dont' know why the system wouldn't be able to tell the exact pressure in each tire individually. My wife's 2007 Impala did it, and it was instantaneous.. Your 2008 has sensors in each wheel that transmit to a receiver in the vehicle, so Lexus should have been able to do it that way.

Earlier systems used some method of the amount of tire rotations relating to the amount of air in the tire or something.

Again, the 2006 DOES NOT have a TPMS system (not event the counting tire rotation system)

[RX400h]

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?

I agree with Lemon - there is no tire pressure monitoring system in our 2006 RX400hs, so your comment about Toyota's lack of common sense does not apply in this case. What I was trying to say earlier is that it seemed like you didn't have anything major to complain about, so you singled out the non-existant tire pressure monitoring system. When people ask me why I don't complain about the rain here in San Diego, I tell them I grew up in CT. While that in of itself doesn't make the weather here, perfect, it does help to keep my complaining to a minimum! ;)

[cduluk]

I didn't know the 06's didn't come with the system

But it is true there is a 20 minute delay before the computer alerts you to a flat or problem, as it's happened to me. In fact, if you remove your sensors and drive around, you won't get any warning light until exactly 20 minutes in DRIVE has passed.

If they made it any more sensitive that light would be flashing every 5 seconds. The sensors receive different data depending on the situation- if you hit bumps, go faster, slower, etc. It records data constantly but has to deal with the outliers. If it detects low pressure for a long period of time (in this case 20 minutes) it will then give you a positive warning.

Why they couldn't make it 5 minutes, i don't know...

[pauljcl]

I didn't know the 06's didn't come with the system

But it is true there is a 20 minute delay before the computer alerts you to a flat or problem, as it's happened to me. In fact, if you remove your sensors and drive around, you won't get any warning light until exactly 20 minutes in DRIVE has passed.

If they made it any more sensitive that light would be flashing every 5 seconds. The sensors receive different data depending on the situation- if you hit bumps, go faster, slower, etc. It records data constantly but has to deal with the outliers. If it detects low pressure for a long period of time (in this case 20 minutes) it will then give you a positive warning.

Why they couldn't make it 5 minutes, i don't know...

My 2005 BMW also came with the early TMPS, which measures the rotation speeds of the wheels and flags if a difference suddenly develops. The system is actually quite sensitive, and notifies with even a small drop in pressure, and does so quite quickly. In my RX (2009) the TMPS system was also pretty sensitive: when I bought the car, the dealer had left the tires under-inflated (27psi) and, coming from dinner a cold (..in FL!) evening the day I bought the car, the light flashed as I started the car. (i.e. no 20mns in Drive).

[skyfish400h]

Why would anyone need/expect the car to tell the driver there is a flat when it occurred suddenly? Wouldn't it be always be obvious at that point?

All these monitoring systems (regardless of the technology) are used to warn the driver of a slow leak that may lead to putting many, many miles on an under inflated tire. That scenario is insidious and dangerous because it may not be obvious to the driver, but may lead to sudden tire failure (at high speed in particular) and subsequent roll over... remember the Ford Explorers?

Just trying to inject a little common sense into the discussion and reset the expectations to rational levels.

[lemon]

Why would anyone need/expect the car to tell the driver there is a flat when it occurred suddenly? Wouldn't it be always be obvious at that point?

All these monitoring systems (regardless of the technology) are used to warn the driver of a slow leak that may lead to putting many, many miles on an under inflated tire. That scenario is insidious and dangerous because it may not be obvious to the driver, but may lead to sudden tire failure (at high speed in particular) and subsequent roll over... remember the Ford Explorers?

Just trying to inject a little common sense into the discussion and reset the expectations to rational levels.

The only time I could imagine 'needing' the TPMS to warn of a completely flat tire, would be if one was using run flat tires.

Regardless, even with a TPMS, I would still check the tire pressures manually with a decent gauge on a regular basis.

[pauljcl]

Why would anyone need/expect the car to tell the driver there is a flat when it occurred suddenly? Wouldn't it be always be obvious at that point?

All these monitoring systems (regardless of the technology) are used to warn the driver of a slow leak that may lead to putting many, many miles on an under inflated tire. That scenario is insidious and dangerous because it may not be obvious to the driver, but may lead to sudden tire failure (at high speed in particular) and subsequent roll over... remember the Ford Explorers?

Just trying to inject a little common sense into the discussion and reset the expectations to rational levels.

The only time I could imagine 'needing' the TPMS to warn of a completely flat tire, would be if one was using run flat tires.

Regardless, even with a TPMS, I would still check the tire pressures manually with a decent gauge on a regular basis.

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