Tyre deflation warning constantly coming on.

[ratherbecycling]

My Jazz triggered a tyre deflation warning. Checked 4 tyre pressures - all were within 0.5psi of what they should be. Reset the warning. Drove about 50 miles at max 60mph. Deflation warning triggered again.

Rechecked all 4 tyres (when tyres had cooled) with same digital pressure gauge, and all were exactly the same as they were two days previously. Reset it again

I did have a sticky brake calliper replaced earlier in the year, but have since regularly checked that none of the wheels is getting hot.   

Plus - before the calliper was replaced and the wheel got hot, the hot wheel did NOT trigger the deflation warning. (That makes sense actually, because the tyre circumference would have IN-creased slightly with the IN-creased pressure, and the Jazz manual specifically says it senses a reduction in tyre pressure, not an increase)

[Basil]

Do you have matching tyres i.e. make and amount of wear ?

[Webley]

Scan for ABS codes.
They may have damaged the wiring when changing the caliper causing an intermittent fault.Ask me how I know.
As previously mentioned having different types of unevenly worn ones can also cause this.

[BadgerMk3]

Plus - before the calliper was replaced and the wheel got hot, the hot wheel did NOT trigger the deflation warning. (That makes sense actually, because the tyre circumference would have IN-creased slightly with the IN-creased pressure, and the Jazz manual specifically says it senses a reduction in tyre pressure, not an increase)

That's true, but you may have to look at it from a different angle.

Obviously I'm not privvy to the algorithms used, but based on knowledge gained on with another car brand, the hotter wheel itself may not trigger the deflation warning, but the increased difference in pulses between that and the other cooler wheels may well do.

When I had my Jazz, I regularly checked and adjusted the tyre pressures accordingly. Each time I reset the deflation system and drove a good few miles over varying road conditions and speeds to give the system a wide range of reference data.

During my ownership I replaced the tyres once, as a full set. I don't recall suffering the same symptoms that many seem to do on here.

[ColinB]

In the first 10 years of owning my car, I had just 2 or 3 DWS false alarms, so I felt quite smug about not suffering the constant issues reported by others. But over the last few months, I've had at least one on every motorway trip. Tyre pressures always OK, DWS recalibrated, but a bit later it sounds off again.

The only significant difference between those journeys and the many previous ones is that they were during the recent heatwaves. The weather's cooled off now, and I've just finished a 350-odd mile round trip - much of which was at motorway speeds, including the same sections which generated false alarms earlier - without any problem at all. So we seem to be back to normal.

So what was going on? Higher ambient temperatures would mean that the tyre pressures would be higher than normal, and the handbook tells us that the DWS doesn't respond to over-inflation. But if the system responds to differences in wheel speeds, how can it tell the difference between a tyre being under inflated and one being over inflated? My guess is that, during a journey in the heatwave, there were occasions when one or more wheels were in full sun and the others weren't, and this differential was enough to trigger the DWS alarm. Doubtless other theories are available.

[Kremmen]

I agree that a tyre or 2 in full sun in heatwave conditions is favourite

Would have been interesting to have taken tyre pressures soon after

[ColinB]

Would have been interesting to have taken tyre pressures soon after

I did the first couple of times, but didn't bother after that. They were always pretty even all round, but higher than normal because (a) there was a 35-40 deg C heatwave and (b) I'd just pulled off a motorway.

My main point is that I'm starting to doubt the handbook's assertion that the system doesn't respond to over-inflation, because all the factors in play here (ambient temperature, high-speed running) would increase rather than decrease one or more tyre pressures.

[Kremmen]

Yes

Like you, I always assumed it detected changes in rotation compared with the initialised saved readings on a wheel by wheel basis and probably on the same axle

[Lord Voltermore]

I doubt the system (on the mk3 at least) is smart enough to know the difference between one  tyre  being under inflated  due to air loss  , and  one or more tyres  having a higher than normal  pressure  (sunny side of car, overheated brake, faulty or different pressure gauge used etc)

The system just compares wheel rotations, regardless of the road speed.  If one or two tyres with the highest pressure are now making fewer revolutions than the others  for the  distance covered  (ie rotating slower) the system activates. But how is it to  'know' which of the tyres  are behaving normally. The highest pressure tyre(s)  may in fact be correct for the circumstances and its the others have lost pressure due to a puncture . (The same hazard may puncture more than one tyre)   You dont want a system that would detect one punctured tyre  , but not two,  or three.     

(But of all 4 tyres are punctured  at the same rate it might not detect any anomaly.  So dont drive over Police stingers ,security spikes etc  )

The system is becoming more sophisticated.  It allows for averages, and discrepancies between wheel rotations while taking bends etc , but it doesnt measure tyre pressures, temperature etc.

Personally I still  prefer the indirect system used by Honda.  It saves the need to have expensive wheel sensor valves, which need periodic maintenance and replacement.

[ColinB]

The system just compares wheel rotations, regardless of the road speed.  If one or two tyres with the highest pressure are now making fewer revolutions than the others  for the  distance covered  (ie rotating slower) the system activates.

That's precisely my point. The handbook tells us that the system does not respond to over-inflation (I think the Mk4 handbook says something similar). But if the DWS is just monitoring the difference in rotational speeds, I don't see how it can discriminate between one (or more) tyres being low, and one (or more) tyres being high: both scenarios would have a difference between wheels. So it's response to unusual high pressures must be the same as for low pressures, ie it generates a warning which is exactly what I experienced at high speed in very hot weather. The handbook seems to be misleading if not downright wrong.

[Kremmen]

I picked up a screw in my 2009 Civic, rear offside

A very very slow puncture as the TPMS didn't pick it up but I did when washing as it was on the bend of face to tyre wall

They couldn't save the tyre so fitted a new one

They didn't trigger the initialise and the tyre was of a totally different type. The others had a radial pattern but the new one had V shaped grooves

The alleged technicians at Ruislip Honda also pumped it up to 39 when it should have been 30

Within half a mile TPMS triggered

I posted about it at the time : https://www.civinfo.com/threads/tyre-pressure-monitoring-system-tpms.415358/?post_id=5402632#post-5402632

[Toptek]

My assumption is that when you reset the TPMS it is based upon all tyres being checked and the pressure set correctly. The following part of the procedure, driving at various speeds, turns and bends etc teaches the system how each wheel is performing rotation wise and can determine any change from the calibrated values.
There are variables to consider such as hot/cold weather, motorway heating, which may not be equal to each tyre, hence a change to what it expects.
I have checked the tyre pressure in summer and winter and needed to reset for both.
My issue is a front tyre losing pressure over a few months, more than the other three. It has been into a reputable local tyre fitters who state it's due to corrosion on the rim.
I might check it shortly and try to preempt it activating.