How trustworthy is the TPMS ?

Evening
Had low tyre pressure warning few days ago in a cold morning. Didn't use the car since. Tried to reset the warning today but found out the TPMS readings is 3 bar less than from a pump gauge. Same result from 2 different pumps.
Anyone has experienced similar discrepancy?
Could it be faulty sensors but all 4 of them seems too much coincidence!
Any comments in addition to just take the car back to the dealer for a check up and recalibration?
Thank you
Ben

Mine seem to be pretty accurate compared to my digital pressure gauge.

I think your pump gauge is more likely inaccurate than the TPMS. I find TPMS agrees with my good quality hand held gauge.

GeorgeC wrote: I agree with Bill and Chris.

I find pumps a bit off to the extent where, out 3, one (a Presta fitting) up to 100psi is spot on,
the other two (Schrader fittings) are +8 and -2 psi respectively, at 30psi!
The new Digital gauge is spot on!

These are the pumps I used with digital gauge. Are the gauges inaccurate?
Thanks
Ben

Hi,

When you say 3 bar out do you mean 3 PSI? Gauges fitted to pumps are not really all that accurate, they even say use a good quality gauge to check the tyre pressure.

+/- 1 or 2 PSI is not really a problem just as long as they are all the same. I doubt that TPMS is within +/- 1 PSI either. Get a good gauge and if possible get it checked. The pumps at garage forecourts should be checked and calibrated from time to time otherwise they would run in to trouble if someone had an accident.

TPMS is most useful for spotting a leak, either slow or fast given that none of us do the weekly check anymore. Same with the oil for and water for most people, gets checked when it goes in for a service.

I doubt that TPMS is within +/- 1 PSI

Apologies, it was psi not bar.
TPMS gave warning, all 4 tyres dropped to 23 psi in a fairly cold morning few days ago. Left the car alone then pumped the tyres up to 27 yesterday afternoon but the car still showed 24 then to 25 for the front after 10 minutes run. The rear remained the same at 24.
The TPMS seems reset at around 24 psi.

I'd suggest that TPMS isn't very trustworthy - I have set my tyre pressures (at cold) on a number of occasions, double checked the pressures using a range of gauges, reset the TPMS using Suzuki instructions - and invariably end up with the TPMS showing different readings. It appears to be another case of 'technology looking for a home' - could easily live without it!

Bob1050, how far out is the TPMS? I wouldn't expect it to be spot on to 1 PSI, but should be close? The point of TPMS is not to be absolutely accurate but to give an indication of changes in tyre pressure, going up when hot and down when you have a leak. Do you get temperature as well, I do on my after market, it is interesting you can see the temperature rise after driving.

Are all of the TPMS out the same way by about the same values? E.g. if you set 23 PSI on all four does all of the TPMS read 21 PSI or are they scattered, some read 21, others read 25?

I would expect them to be +/- 2 PSI.

I have after market TPMS on a GEN3, they are within +/- 2PSI worst case to my [accurate] gauge. most +/- 1 PSI.

First sign of winter - when your Jimny nags you about tyre pressures...

Just checked my tyre pressures and they were all around 24.5 psi. Normal is 26 psi. Warning light hadn't come on.

Roger

DrRobin wrote: Bob1050, how far out is the TPMS? I wouldn't expect it to be spot on to 1 PSI, but should be close? The point of TPMS is not to be absolutely accurate but to give an indication of changes in tyre pressure, going up when hot and down when you have a leak. Do you get temperature as well, I do on my after market, it is interesting you can see the temperature rise after driving.

Are all of the TPMS out the same way by about the same values? E.g. if you set 23 PSI on all four does all of the TPMS read 21 PSI or are they scattered, some read 21, others read 25?

I would expect them to be +/- 2 PSI.

I have after market TPMS on a GEN3, they are within +/- 2PSI worst case to my [accurate] gauge. most +/- 1 PSI.

Difference on one axle can be TPMS showing 2psi differential between nearside and offside - irritating after checking using gauges that show all is well before TPMS reset. Standard system only shows pressure not temperature of individual tyres. Even if a pressure gauge is not calibrated to be accurate to within less than 1 psig - it should be consistently inaccurate.