Tire pressure warning system

[brs29]

Hi all,

Recently bought a used 2015 IS 300H and I'm loving it so far - 2 owners with 50k miles, full service history at Lexus, and only done 500 miles in the past 12 months as the previous owner was working from home.

The only thing nagging me is the Tire Pressure Warning System - the light is permanently illuminated, despite 4 new tires being recently fitted (Sept 2020), and all 4 inflated to the correct pressure. There are no evident leaks and it's safe to drive.

I've tried resetting it following the instructions in the Handbook but to no avail. Is the warning system hyper-sensitive or something? Is it safe to ignore it?

 

[Rabbers]

This has happened to me twice and was on both occasions attributable to a single faulty sensor replaced, fortunately for me, when the cars were 

still under warranty.  If you don't have quick access to a Lexus dealer a good tyre shop should be able to identify the problem.  Safety is not an issue

if the pressures are OK, but the permanently illuminated warning light is probably as big a source of irritation for you as it was for me.   Based on my

experiences, I wouldn't expect a Lexus dealer to have replacement sensors immediately available from stock.

[ianhu]

Hi. 

I once had similar situation. Unfortunately for me the men at said garage treat all wheels and tyres and tpms as one and tried to tell me the car will learn the new tpms sensor they had replaced "just drive it around and it will sort itself out". Yeah right, after a week still had indicator on dash so I know how annoying it is. I also now know they had sh*t for brains. If they had used their brains they could have picked the phone up where lexus would have told them any new tpms needs coding to the car. Usually done with teachsteam. (Btw that's not the amazon cheapo job, reason being is that the software works but the cable has some connections disabled. Buying proper cable costing £70 got all working.) Anyway I got said garage to give me all four tmps id's and I programmed them into techstream. Since then no tpms light in a year. 

Lesson learnt. Don't use garages that just shift tyres and nowt else. 

[Brechin Slate]

1 hour ago, brs29 said:

I've tried resetting it following the instructions in the Handbook but to no avail. Is the warning system hyper-sensitive or something? Is it safe to ignore it?

As already mentioned, it's safe to drive as long as you know your tyre pressures are correct.  Was the warning light on when you bought the car or has it happened since?  It could be that one or more sensors were damaged during the tyre change. If you have access to an OBD reader like Carista you can check the sensors are reading, see pic.  It will give you an idea of where to start.

 

[ianhu]

6 minutes ago, ianhu said:

Hi. 

I once had similar situation. Unfortunately for me the men at said garage treat all wheels and tyres and tpms as one and tried to tell me the car will learn the new tpms sensor they had replaced "just drive it around and it will sort itself out". Yeah right, after a week still had indicator on dash so I know how annoying it is. I also now know they had sh*t for brains. If they had used their brains they could have picked the phone up where lexus would have told them any new tpms needs coding to the car. Usually done with teachsteam. (Btw that's not the amazon cheapo job, reason being is that the software works but the cable has some connections disabled. Buying proper cable costing £70 got all working.) Anyway I got said garage to give me all four tmps id's and I programmed them into techstream. Since then no tpms light in a year. 

Lesson learnt. Don't use garages that just shift tyres and nowt else. 

I hope lexus has made their newer cars learn the damn things. Certainly my is300h 2014 didn't 

[brs29]

Thanks for all the replies.

The warning light was on when I bought the car - the owner didn't know much about it (he'd driven it twice in the past 4 months due to a new company car, and wasn't too clued up about cars in general). I checked the service history and the last Lexus service was in Sept 2020 at 50,000 miles, which it passed fine. After buying I figured I'd just check the tyre pressures, reset the TPWS and it would fix itself, but the light refuses to go off. I don't have an OBD reader so can't check the sensors myself.

I'm not overly keen to pay for a diagnosis and possible replacement sensor so soon, I can probably live with it until the next service at 60,000 miles. If it was the sensor at fault, would a replacement be included in the service cost?

[Rabbers]

3 minutes ago, brs29 said:

 

3 minutes ago, brs29 said:

.....I can probably live with it until the next service at 60,000 miles. If it was the sensor at fault, would a replacement be included in the service cost?

I think the diagnosis of a faulty sensor would be included in the cost of service but that you would be charged for the replacement if needed.

[Brechin Slate]

23 minutes ago, brs29 said:

Thanks for all the replies.

The warning light was on when I bought the car - the owner didn't know much about it (he'd driven it twice in the past 4 months due to a new company car, and wasn't too clued up about cars in general). I checked the service history and the last Lexus service was in Sept 2020 at 50,000 miles, which it passed fine. After buying I figured I'd just check the tyre pressures, reset the TPWS and it would fix itself, but the light refuses to go off. I don't have an OBD reader so can't check the sensors myself.

I'm not overly keen to pay for a diagnosis and possible replacement sensor so soon, I can probably live with it until the next service at 60,000 miles. If it was the sensor at fault, would a replacement be included in the service cost?

Understand that you may not want to part with any cash but for £25 you could buy a Carista and follow the video below.  You get full free functionality for the first month.  It might give you peace of mind knowing if more than one sensor is affected and you'd have a good diagnosis tool for use in the future 🙂

 

[brs29]

That Carista dongle has always intrigued me so I've just ordered one, will be useful to share with my dad's car also.

I'll report back and let you know if the sensors are good or bad! 🙂

[Thackeray]

1 hour ago, brs29 said:

That Carista dongle has always intrigued me so I've just ordered one, will be useful to share with my dad's car also.

One thing to bear in mind is that it draws power whenever it's plugged in. I once ran my 12v Battery down to 11.4v when I forgot to take out the Carista adapter and left the car unused for two or three days. Fortunately, the car would still start.

On the plus side, when you get yours you can also use it with the Hybrid Assistant app, which is really great for getting to know how the hybrid system works. Maybe this isn't your first hybrid, but if it is Hybrid Assistant can tell you more than you ever wanted to know about what the hybrid system is doing. It's a free app, developed in Italy by hybrid enthusiasts. Here's a link to their webpage. https://hybridassistant.blogspot.com/p/screenshots.html

 

 

[brs29]

Thanks, I'll remember to unplug it when finished. To use the Hybrid Assistant and Tire Assistant app (free unlike Carista), do you have to pair your phone to the dongle via Bluetooth first? I presume it doesn't auto-connect like the Carista app.

 

[Thackeray]

1 hour ago, brs29 said:

To use the Hybrid Assistant and Tire Assistant app (free unlike Carista), do you have to pair your phone to the dongle via Bluetooth first? I presume it doesn't auto-connect like the Carista app.

When I use Hybrid Assistant or Tire Assistant they both connect automatically. I can't remember for certain but I think this is because on the first use I paired my phlone with the Carista dongle. After that is done once, I imagine any app on the phone that uses data from the dongle will work without any need for further setting up. The Tire Assistant is handy for checking pressures without getting your hands dirty. But I don't think it allows you to change the sensor ID like the Carista app. But you used to get a month's free use of the Carista app. If that's still the case you can use facilities like that for a while without paying.

[brs29]

Guys, problem solved, and feel a bit stupid now! The gauge on my trusty old pump had gone, so all 4 tyres were showing 36 psi when their actual pressure was 32 psi, and the tires were way under-inflated. I'm surprised the previous owner hadn't noticed to be honest, but then he hardly used the car in the last year. Confirmed they were all 32 psi by borrowing my neighbour's pump and also cross checking at a local garage. All inflated to 36 psi now, reset the TPWS and the light is off. 

I'll still play around with the Carista once it comes tomorrow, will be handy to get the sensor IDs for future reference.

Thanks for all the replies, this is a great community.

[Brechin Slate]

18 minutes ago, brs29 said:

Thanks for all the replies, this is a great community

Glad it all worked out, minimal expense too which is always a bonus!

[paulrnx]

Better to invest in a tyre pressure gauge. The gauges attached to pumps are not that accurate in my experience. Not sure why pumping up to 36 psi has now fixed the problem given that you were resetting the TPMS before? You could have all four at 32 psi and they should still register no issues if you’d reset the TPMS at these pressures.

[Brechin Slate]

3 minutes ago, paulrnx said:

Better to invest in a tyre pressure gauge. The gauges attached to pumps are not that accurate in my experience. Not sure why pumping up to 36 psi has now fixed the problem given that you were resetting the TPMS before? You could have all four at 32 psi and they should still register no issues if you’d reset the TPMS at these pressures.

👍 +1 on this. See link below:

 

[brs29]

24 minutes ago, paulrnx said:

Not sure why pumping up to 36 psi has now fixed the problem given that you were resetting the TPMS before? You could have all four at 32 psi and they should still register no issues if you’d reset the TPMS at these pressures.

Good point, I can only assume that the gauge on my pump was faulty to the extent that it caused enough of a mismatch between the tyres to trigger the TPMS - e.g. they might have all read 36 but were actually 32, 31.5, 34 and 33. When I said they all read 32 psi on my neighbour's pump/gauge, I meant "close to 32 psi", one was actually 31 psi and one slightly above, I think 32.6 psi. They were just under-inflated by around 4 psi on average.

My trusty old Michelin foot pump is around 60 years old, one of the original Made-in-France "they don't build them the same nowadays", been passed down 3 generations and still worked extremely accurately up until recently. I always used it on bicycle tyres, 34 psi and confirmed exactly 34 psi via a separate pressure gauge (which I lent to a friend and am still waiting to get back, hence why I didn't cross-check the car tyres before - I would have normally but was solely relying on the pump gauge). If I don't get the tyre pressure gauge back soon then I'll order a new one (new foot pump is already on the way!)

 

 

[brs29]

Update: The Carista app showed tyre pressures as 35.93 psi, 36.02 psi, 36.08 psi and 35.96 psi. Pretty bang on.

[LenT]

8 hours ago, Brechin Slate said:

👍 +1 on this. See link below:

 

Regarding a tyre gauge recommendation, I would endorse Mike’s reference to this previous post.  On it I (and others) named the TireTek gauge, supplied by Odyseaco and fulfilled by amazon.

Used it recently and still impressed.  

I also recently replaced an elderly Halfords inflator with one called Skey.  Instead of plugging into what we used to call the ‘cigar lighter’ it has its own rechargeable Battery.  

The accessory connection on the Halfords unit was proving increasingly unreliable.  So I thought an inflator with its own power supply was a better idea.

Haven’t used it in anger yet, but a quick test showed it was well up to the task.

[paulrnx]

12 hours ago, brs29 said:

Good point, I can only assume that the gauge on my pump was faulty to the extent that it caused enough of a mismatch between the tyres to trigger the TPMS - e.g. they might have all read 36 but were actually 32, 31.5, 34 and 33. When I said they all read 32 psi on my neighbour's pump/gauge, I meant "close to 32 psi", one was actually 31 psi and one slightly above, I think 32.6 psi. They were just under-inflated by around 4 psi on average.

My trusty old Michelin foot pump is around 60 years old, one of the original Made-in-France "they don't build them the same nowadays", been passed down 3 generations and still worked extremely accurately up until recently. I always used it on bicycle tyres, 34 psi and confirmed exactly 34 psi via a separate pressure gauge (which I lent to a friend and am still waiting to get back, hence why I didn't cross-check the car tyres before - I would have normally but was solely relying on the pump gauge). If I don't get the tyre pressure gauge back soon then I'll order a new one (new foot pump is already on the way!)

 

 

Doesn’t really matter what the pressures were nor whether each tyre had the same pressure or different. You pump them up, check pressures and reset the TPMS and it starts monitoring from this measured reset point. The whole point of resetting the TPMS is to reset the measurement point at which each individual is then monitored from. If the pressure drops in one or more tyres from that reset point, the TPMS will then trigger. I’m pretty sure this is how it works. It has to be the case when you think about it. If running a full load you would add air to the tyres and reset the TPMS to measure from this increased setting. The TPMS doesn’t measure from and report a deviation to some factory pre-determined pressure, it measures from and reports deviations to the pressure in each tyre at the time of the last reset.

[brs29]

1 hour ago, paulrnx said:

Doesn’t really matter what the pressures were nor whether each tyre had the same pressure or different. You pump them up, check pressures and reset the TPMS and it starts monitoring from this measured reset point. The whole point of resetting the TPMS is to reset the measurement point at which each individual is then monitored from. If the pressure drops in one or more tyres from that reset point, the TPMS will then trigger. I’m pretty sure this is how it works. It has to be the case when you think about it. If running a full load you would add air to the tyres and reset the TPMS to measure from this increased setting. The TPMS doesn’t measure from and report a deviation to some factory pre-determined pressure, it measures from and reports deviations to the pressure in each tyre at the time of the last reset.

I think you're right. In that case, I'm not really sure what the problem was as the TPMS reset should have caused the light to go off, even if the tyres were under inflated. 

With all 4 tyres inflated to the correct pressure now I'll monitor it and see how it goes. Definitely no slow punctures and the light hasn't come on again since.

 

[Slicendice]

I just had the warning light come on (Lexus IS 300h 2017).  Seemed like a slow pressure leak as the pressure would drop over a few days and the light came back on.  So ended up buying a new tyre.  The new tyre did the same thing :/.   Had a different tyre company come and look, and the guy said it was the TPM sensor / valve.  Simple test was to spray the valve with some very soapy water, bubbles started to appear.   A closer inspection revealed someone had bodged a seal on the sensor.  So it was replaced with a proper washer, and the problem was gone.  Wish I'd have got the first guy to check the TPM afterwards.  I suspect they didn't want to touch is as they don't replace them or something, plus they got a good tyre from me...

 

 

[Mincey]

Mine came on this morning. Checked with Tire Assistant and a gauge and all are ok. Now I need to follow the advice of the wise @royoftherovers and look in the manual, as I can't find the reset switch!

 

[Mincey]

Well, I'm sure you're all dying for an update. I found the switch and reset the indicator. Just been out for a spin and it's behaving itself. 

[royoftherovers]

1 hour ago, Mincey said:

Well, I'm sure you're all dying for an update. I found the switch and reset the indicator. Just been out for a spin and it's behaving itself. 

Aren`t Handbooks wonderful accessories James ?