tpms TPMS calibration question

Shahpor · March 17, 2020

Hello all,

I am experiencing something odd with my TPMS system on my GS, so I am hoping someone can shed some light on it.

Basically, I have been having a problem with a slow puncture on my NSF tyre. As such I have been pumping it up myself, and a few days ago I took it to a garage to have a look at it. They diagnosed a leaky valve seal and tightened it slightly which seems to have stopped the leak.

Anyhow, since this started I have noticed that the reading for that tyre has been higher on the dash display then the pump that I used. At first I thought it might be the pump that was misreading, but when the garage did the repair they also added some air, which should have been 2.2 Bar, but the car is reading 2.5 Bar.

Upon arriving home, I attempted to reset the system - ignition on, hold the under dash TPMS switch until the warning light blinks 3 times - but it has made no difference.

So, I was wondering if anyone had experienced this issue before and what the possible solution might be? The obvious one is the replace the sensor, but I am loathed to change something that might be working correctly, so I was hoping someone might have an alternate suggestion?

Thanks.

johnatg · March 17, 2020

Not based on experience, but I think I would try deflating the tyre partly so that a fault shows on the dash display, then pump the tyre up again and reset.

Shahpor · March 17, 2020

Thanks for the suggestion John, but I did try that whilst I was pumping the tyre up before getting it fixed.

The warning came up when the pressure fell below 2 Bar, so I pumped it up to 2.2 Bar, but when I got home it was over reading, so I tried resetting it but it didn't change.

NemesisUK · March 17, 2020

Remember only check the tyre pressures when the tyres are cold, best first thing in the morning before being driven for the first time. Otherwise allow to stand for a good couple of hours after being driven.

Shahpor · March 17, 2020

Actually Peter, what you suggest has been well illustrated since I have been keeping a closer eye on it.

The pressures do increase significantly once you have driven for a time, but unfortunately, for me at least, the variance remains the same. This means that my NSF tyre reads roughly 2.5 Bar whilst cold, but it does increase to 2.7 Bar (!) when I am on the motorway. The other tyres will increase from about 2.2 Bar to about 2.4 Bar, so it appears consistent.

Another interesting effect is the outside temperature. On very cold mornings (1 - 5C) the pressure might drop to 2 Bar but since it has warmed up it has returned to normal.

Either way, thanks for your suggestion.

NemesisUK · March 18, 2020

Simply Boyle's law in action ...

Shahpor · August 21, 2020

Strange update on this one as well.

The pressure reading never did equalise in the end, but it didn't seem to be a problem, so I left it.

Anyway, a week or so ago, I started seeing the TPMS warning light again for the same wheel. However, this time it read the correct pressure (about 2.2 Bar) as the rest of the wheels.

The other odd thing is that it will go away after roughly 20-30 minutes of driving every morning during my commute. It will then generally stay working properly for the rest of the day but the error will come back the next morning. Again, 20-30 minutes in and it goes back to normal....

Anyone have any ideas? I could put it into the dealer, but since they are more than 30 minutes away the error would be gone when I get there and I can't afford to leave it overnight since they are not currently giving out loan cars.

Thanks.

johnatg · August 21, 2020

Have you set all tyres to correct pressures then press the button under the dash?

Sent from my PSP7551DUO using Tapatalk

Mossypossy · August 22, 2020

There seems to be a 20 minute timer in the tpms software.

When I clear my TPMS fault code it will always ping back after 20 mins driving.

(I need to find id codes for my senders)

Shahpor · August 22, 2020

Thanks chaps.

I did the reset again as John suggested, so I suppose I will have to wait until tomorrow to see if it has worked or not.

Shahpor · August 25, 2020

Well, so far so good, so thanks for the tip John.

I do still think there is something not right about the NSF sensor, but for now it is happy enough (even though it still doesn't appear to read the correct pressure) so I will wait and see what happens.

KayCee · August 26, 2020

Shahpor

do you think that being as that tyre kept going down and was sending signal it may have depleted that Battery in that wheel more than the others

the reason i say this is when i bought my first gs300 the nsf was very pappy ie low on air so when i said i was interested he had the tyre repaired there was a nail in it

after i bought it approx 4 month later the same problem you had appeared so had he sensor replaced they said Battery was flat was ok after that

Shahpor · August 26, 2020

Hi Robert,

That is an interesting idea that I hadn't considered. It could very well be the case, so if it does start giving me grief again I will probably just get it changed.

Thanks for the suggestion :thumbs_up:

NemesisUK · August 26, 2020

I'd have thought the sensors would be constantly sending, at regular intervals, so the ECU can tell if one becomes faulty?

ColinBarber · August 26, 2020

1 hour ago, NemesisUK said:

I'd have thought the sensors would be constantly sending, at regular intervals, so the ECU can tell if one becomes faulty?

Correct. Each one transmits every 1.5 minutes when the wheel isn't moving, or every 15 seconds if it is.

Batteries are meant to last 10 years.

ColinBarber · August 26, 2020

On 8/22/2020 at 2:43 AM, Mossypossy said:

There seems to be a 20 minute timer in the tpms software.

When I clear my TPMS fault code it will always ping back after 20 mins driving.

(I need to find id codes for my senders)

From the system description:

"After running for approximately 20 minutes, if the tire pressure warning light blinks and then comes on after that, the initialization has not been completed normally, so it is necessary to re-initialize"

KayCee · August 27, 2020

I stand corrected Colin I was just saying this as this was my experience of it

4 month later the tyre that had the nail in, the sensor had to be replaced as according to Lexus the Battery was flat.

ColinBarber · August 27, 2020

2 hours ago, KayCee said:

I stand corrected Colin I was just saying this as this was my experience of it

4 month later the tyre that had the nail in, the sensor had to be replaced as according to Lexus the battery was flat.

I doubt the dealer took the trouble to pull it apart to measure the Battery voltage - more likely it wasn't working, they replaced it and assumed the Battery was dead. That may have been the case but it also could have been an electronics failure, it was damaged slightly when you had the tyre replaced etc.

Techstream will give Battery level information if the unit is working, but obviously if the thing is completely dead then that isn't possible.