brs29

Funny this post should come up as I was just about to post too. Last week during the snow we had, my TPMS light came on - assumed it was the cold weather and yes, after driving 10 miles the light went off. In the evening I manually checked my tires with a gauge, all 36 psi, and realising I'd not used my Carista for over a year, thought I'd plug it in to see what the sensors were measuring - all confirmed as 36 psi also. Next morning, my TPMS light started blinking (indicating a fault) then went solid after 2 minutes of blinking. Plugged my Carista back in and one of the sensors was showing no reading with an error message. Now my IS300H has done close to 100k miles and the batteries are supposed to last 80k miles, so it didn't come as much of a surprise. I was away with work and in a different city to my usual Lexus dealer, so popped into another Lexus dealer after work and explained the situation. I plan to keep the car until it's done 200k miles so wanted a genuine OEM Lexus sensor, not a third party one. The service guy interrupted me mid-sentence and asked if I'd plugged a Carista in recently - to which I replied yes. He laughed and said there's nothing wrong with my sensors, they could fix it within minutes. Plugged into Techstream, they reset all 4 sensors, checked the batteries (all showing good health still) - TPMS light off and no more faults. According to that Lexus dealer, when you put a Carista in, it can only gain access to the tyre sensors by "re-registering" the TPMS sensor codes with the same sensor IDs it reads off. But there seems to be a bug and one of my sensor codes had been re-registered incorrectly, looks like a zero (0) had been put in as a capital letter O. Must stress that I had done nothing on the Carista app except click "Read tyre pressure sensors", I hadn't clicked anything to register new sensors and it seems this was done automatically in the background by the dongle/app trying to gain access. I was advised not to plug the Carista in again, otherwise I'd face the same problem unless the bug is fixed!

It's happened to me several times - the trick is to fully open the rear window from its own switch (keeping the switch pressed down for 6+ seconds after it's fully opened), then fully close it again (keeping the switch pressed for 6+ seconds after fully closed). This seems to reset the window and the driver's switches can then control it again.

I was initially forced to use Autoglass by my insurer (Admiral) on a previous car (around 6 years ago) - they did an absolutely awful job, it was obviously rushed and caused all sorts of problems in the weeks after. Luckily Admiral was very good about it and arranged a different replacement at another company (forget the name sorry), and it was both professional and long-lasting. Wouldn't use Autoglass again.

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.

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

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!)

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.

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.

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! 🙂

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?

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?