Tyre Pressure Monitoring

Steverally · March 4, 2015

Hi, New to this forum as only had my IS300h for just over a week, previously had a CT200h.

Hoping someone here will be able to answer regards TPM :

I'm not happy having a bottle of gunk to repair tyres, so intend to purchase a set of winter wheels and tyres for winter use and to double up as a spare wheel option - If I fit normal valves what will happen to the TPM indicator in the car - will it remain on permanently and is there a warning buzzer that will drive me crazy. Can I just press the reset button?

Secondly - I would like to fill my current tyres with Nitrogen - any problems with this regards the TPM valves?

Looking forward to your comments, and if the responses are as good as the feedback experienced in the CT forum I'll be delighted

Thanks

Steve

DJP · March 4, 2015

I can't answer most of your questions but there is no buzzer. Just a yellow light that goes off on start up and comes straight back on. It doesn't even flash and I'm not sure, but have a feeling it gives up after about 15 mins driving. Then comes back next time you start.

Sent from my Iphone using Lexus OC

Bratman91 · March 4, 2015

When my TPM light came on, it is steady light and it did indeed go out after 10 minutes or so. However, I concluded that this was because the tyres had heated up and, thus, caused a pressure increase. After I got home, I put some air in all the tyres so I can't say whether or not the light would have come on again after starting up the next time.

Bratman91 · March 4, 2015

Would filling up with nitrogen invalidate any gaurantees on the tyres?

Steve44 · March 5, 2015

Last time the tpms light came on mine, it was on for the whole journey, 2+hrs. There wasn't anything wrong with the tyre, just slightly below pressure.

Bob99 · March 5, 2015

TPMS light will stay on all the time if a sensor can't be detected, but I was told by a tyre dealer that the main dealer can override / turn off the warning light, don't know if that is true.

Steverally · March 5, 2015

Thanks for comments so far.

Just found in the manual, in small print, that if the TPM sensors are not registered, then after 10 mins of driving the indicator will 'flash' for 1 minute and then stay on permanently. May just have to live with this.

Still looks like normal valves and a set of eyes and ears - look, listen and feel for problems. Assume TPM's are our EU cousins insisting on making it easy together with bottles of 'gunk'.

Other option, buy set of sensors for winter wheels, but then the dealer has to reprogramme at each swap between summer and winter tyres. Wonder about cost of sensors and reprogramming - Any one any experience of this?

Steve

Steverally · March 5, 2015

Just noticed my 'Fuelly' badge show my old CT... can't seem to change until I do first fill up..just upto 500miles and still a 1/4 full.

Finnlexus · March 10, 2015

The programming has to be one only once, because it's possible to program 8 sensors in the IS. So no need for reprogramming after changing winter/summer tyres.

Steve_L · March 17, 2015

My recent experience with the TPMS has questioned whether it functions correctly. Has anyone else had cause to check tyre pressures without a warning light showing and found the pressure to be low?

I am trying to run my FS Sport at recommended pressure - 2.5 bar - but often find it as low as 2.2. My suspicion is that the monitor is not working. I have tried to reset as advised in the handbook but no success with the button above the pedal.

Anyone else had similar problems?

ColinBarber · March 17, 2015

The reset didn't work or it still isn't warning you of a low pressure?

The system gives you + and - tolerance, so if your system is set at 2.35 bar then you could go as low as 2.2 or higher than 2.5 without an issue. Better to set your pressures to 2.5 and then reset the system.

DJP · March 17, 2015

I think it has a tolerance of a few psi either side of what it's set at. That's been my experience anyway.

Sent from my iPad using Lexus OC

Steve_L · March 17, 2015

Thanks Colin - and David.

I had tried to reset after inflating to 2.5. The book advises that the monitor light comes on to tell you it has reset but mine doesn't. The warning had come on twice in first few months of ownership but doesn't any more.

I suspect I will need to report it when in for service.

ColinBarber · March 20, 2015

You need to press and hold the button in until the light comes on, probably about 5 seconds.

DJP · March 20, 2015

You need to press and hold the button in until the light comes on, probably about 5 seconds.

Press and hold until the light comes on and flashes 3 times. Then sit and wait for a couple of minutes before starting the car. Pretty sure thats the routine the manual gives.

Ian J. Parsley · March 20, 2015

Last winter (my first with the car) I noticed the light come on in the winter every time I started the car and go off after about 10 minutes.

I could see no problem with the tyres so I checked in at Lexus Belfast, and they confirmed there was no problem - the Head of Sales suggested that it takes that long in winter for the tyres to warm up (as noted above) and also said something about grip.

This winter I noticed the light come on again, as last, but in retrospect it never went off again (I didn't really notice that it didn't, tbh - I was so used to it on!) Again I checked the tyres myself and could find nothing wrong; but I also noticed by mpg was down to about 43 (from the usual winter 46) and wondered about how the car was driving - so, to be sure I left the car in with Lexus Belfast to check. I returned two hours later to find that yes, one tyre had a slow puncture.

I am no expert about tyres, but I would note this was fixed free of charge, and reprogrammed as noted above. That suits me!

The other thing I would say is, if in doubt, just pop into the Lexus dealer. They're Number 1 in all the rankings for a reason. [The one exception to that is software updates, about which I inform them rather than the other way around!]

The light is off now, btw!

Steve_L · March 20, 2015

Tried a reset again this evening after my short drive home. Conclusion is I must be getting paranoid about my tyres!

I had convinced myself the bumpy ride over bad surfaces was due to low pressure, but found all tyres to be between 37 and 38 psi and hence OK - allowing for warm up on run home.

I am now asking myself why the bumpy ride? I have found the FSport to be less smooth than my old Series 2 Advance but it seems to pick up even slightest road blemish.

Anyway, back to the tyres as I still can't get the reset to work. Held the button as advised in handbook but there was no flashing light. Is there only one button on the panel above brake pedal?

ColinBarber · March 21, 2015

Yes just the one button on the F Sport, it presses in quite far. Did you have your ignition on?

The F Sport has a harder suspension than the other grades, hence the bumpy ride.

markeyszoo · January 21, 2021

On 3/4/2015 at 1:27 PM, Steverally said:

Hi, New to this forum as only had my IS300h for just over a week, previously had a CT200h.

Hoping someone here will be able to answer regards TPM :

I'm not happy having a bottle of gunk to repair tyres, so intend to purchase a set of winter wheels and tyres for winter use and to double up as a spare wheel option - If I fit normal valves what will happen to the TPM indicator in the car - will it remain on permanently and is there a warning buzzer that will drive me crazy. Can I just press the reset button?

Secondly - I would like to fill my current tyres with Nitrogen - any problems with this regards the TPM valves?

Looking forward to your comments, and if the responses are as good as the feedback experienced in the CT forum I'll be delighted

Thanks

Steve

Air is 78% Nitrogen. Where would you get more?

ColinBarber · January 21, 2021

9 hours ago, markeyszoo said:

Air is 78% Nitrogen. Where would you get more?

Most tyre shops have Nitrogen if you want that instead of air. Tyre pressures are maintained for longer with Nitrogen.

Thackeray · January 21, 2021

My thinking on nitrogen is that it's probably not worth paying for. When you get new tyres they will be filled with 78% nitrogen, as Mike points out. Most of the rest is oxygen and my understanding is that because oxygen molecules are smaller than nitrogen, they can seep through the rubber whereas the nitrogen doesn't, or not so much.

If all the oxygen seeps out and you have to top up the tyres, the lost 22% volume of gas (which was 100% oxygen) is replaced with air (which is 22% oxygen). So after one top-up the oxygen is now about 5% of the total volume of gas (22% of 22%) and nitrogen about 95%. After a second topup the 5% oxygen becomes 1% oxygen and 99% nitrogen. So I'm not sure there's much benefit in paying for nitrogen.

It's different for formula one, of course, where tyre pressures need to be exactly right all the time.