2015 CX-5 TPMS (ABS differential type) light on a hot day

[jiggseob]

Driving home on a hot - for Western Canada - 90F day, and the TPMS light came on. Drove 20 miles home, put vehicle in garage overnight. Check tire pressures in morning, three are 34psi, one is 32 psi. Let the tires down a bit and then aired them up to 34 psi. Checked twice. All 34. Pressed the "TPMS reset" switch for 3 seconds, TPMS light went out then went for a ten-mile drive. TPMS light has stayed off for about 25 miles now.

This is the TPMS system that uses the ABS/Traction control wheel speed sensors to detect the "differential" between wheel speeds. When you press the "TPMS Reset" button, the TPMS computer presumes you have correctly adjusted tire pressures, and the system spends the next several miles "learning" the difference - if any - between the four wheels. Difference would exist if the tires are not perfectly evenly worn; the tiny difference in rolling circumference is compensated for by the TPMS computer during the Reset / initialize process.

Question to the rest of the forum... has anyone else noticed over-sensitivity of the TPMS system on hot days? Any other conditions where TPMS light comes on, and tire pressure found to be normal?

The whole "TPMS" discussion about the lack of usefulness of a system that only reports an "abnormality". Ideally, when I'm driving at 70mph on the highway, and something goes "wrong" with the car, I want/need to know "how wrong is it?" In the case of tire pressure, that means what was the pressure a minute ago, what is it now, and what is it in another few seconds. If its dropping fast, that means get off the freeway NOW. If its dropped 1 psi in the last week, and drops no more psi's in the next hour, that means I can easily make it to the next town or even the next province. Yes, TPMS of this flavour is as close to useless as useless can get.

Thankfully subsequent TPMS systems are more "useful" in that they report actual pressure - albeit 15 seconds ~ a minute or two delayed. More useful than an idiot light, but still not "real-time".

Anyways enough ranting.... I'd be interested to hear of others' experience with over-sensitivity of the differential wheel speed type TPMS.

Thanks.

 

[Chas]

My wife's 2014 CX-5 GT had a similar issue. During the summer, the TPMS light would come on. I kept airing it up, actually to about 36 all round. Dealer finally diagnosed it as air pressure too high on those days approaching 100. He said the TPMS was not just for low pressure. Anyway, we just kept airing up the tires to door panel spec at least 4 times a year, at least when the weather changed, and before long trips. I know you are supposed to check tire pressures every 2 weeks or so, but I get lazy.

 

[HyFlyer]

I've had a few mazda's with the wheel speed sensor type TPMS. Advantages / disadvantages in everything. I've had a couple occasions over the years where the system triggers and I find everything okay (hot day like your experience) and there's been a couple instances of picking up a nail or something and having pressure loss. It is a simple system. Better than nothing though.

There are inexpensive aftermarket systems available and one of the folks here installed a system not too long ago on his car and wrote extensively about his experience. That may be just what you're looking for to keep you "in the know" about your tire pressure real time.

 

[Conrad 16.5]

Driving home on a hot - for Western Canada - 90F day, and the TPMS light came on. Drove 20 miles home, put vehicle in garage overnight. Check tire pressures in morning, three are 34psi, one is 32 psi. Let the tires down a bit and then aired them up to 34 psi. Checked twice. All 34. Pressed the "TPMS reset" switch for 3 seconds, TPMS light went out then went for a ten-mile drive. TPMS light has stayed off for about 25 miles now.

This is the TPMS system that uses the ABS/Traction control wheel speed sensors to detect the "differential" between wheel speeds. When you press the "TPMS Reset" button, the TPMS computer presumes you have correctly adjusted tire pressures, and the system spends the next several miles "learning" the difference - if any - between the four wheels. Difference would exist if the tires are not perfectly evenly worn; the tiny difference in rolling circumference is compensated for by the TPMS computer during the Reset / initialize process.

Question to the rest of the forum... has anyone else noticed over-sensitivity of the TPMS system on hot days? Any other conditions where TPMS light comes on, and tire pressure found to be normal?

The whole "TPMS" discussion about the lack of usefulness of a system that only reports an "abnormality". Ideally, when I'm driving at 70mph on the highway, and something goes "wrong" with the car, I want/need to know "how wrong is it?" In the case of tire pressure, that means what was the pressure a minute ago, what is it now, and what is it in another few seconds. If its dropping fast, that means get off the freeway NOW. If its dropped 1 psi in the last week, and drops no more psi's in the next hour, that means I can easily make it to the next town or even the next province. Yes, TPMS of this flavour is as close to useless as useless can get.

Thankfully subsequent TPMS systems are more "useful" in that they report actual pressure - albeit 15 seconds ~ a minute or two delayed. More useful than an idiot light, but still not "real-time".

Anyways enough ranting.... I'd be interested to hear of others' experience with over-sensitivity of the differential wheel speed type TPMS.

Thanks.

With the tires cold (the next morning) the difference was only 2 psi. If you had checked the tires right away when you got home, the difference would have been greater than 2 psi and that's what triggered the system.

I personally wouldn't have driven 20 miles home without checking to see what's what with the tires.

 

[Jmaz]

Is there a tire pressure sensor in the spare that could trigger a warning light?

 

[jiggseob]

I wouldn't have driven the 20 miles home without at least stopping and visually checking tires. Other person in my family makes different vehicle operating decisions which I am not allowed to question.

With the abs-based wheel speed differential type "TPMS" system, the spare is not part of what is monitored. There are no "sensors" in any of the tires, including the spare.

A later call to the service department of Mazda dealer finds that the TPMS light does come on with a high degree of sensitivity, not related to temperature, but related to ongoing tire wear, every once in a while -10k miles - one should check/adjust pressures to exact amount cold, and then press TPMS reset button, and go for a 10 mile drive so that the system can re-learn the normal rotation of tires to compare against values.

 

[Jack Rabbit]

Too much worry on this. The idiot gauges work fine for slow leaks or winter deflation.

Actual pressures won't help in emergency. I've been in vehicles that the beep went off, and felt flat tire rumbling down. Knowing the numbers didnt help at all. Between fast cars flying up behind you and trying to find place to pull off, by time look at gauge it's only 4 lbs.

 

[jiggseob]

I agree Jack Rabbit, in the case of 35psi to 4 psi over the course of 30 seconds or less, knowing the pressure in real-time won't help much, because the time you see the pressure is down, you are feeling the rumbling. With that situation, the thing that would help most is if the ejector seat D-handle would light up...

Knowing the pressure in real-time would allow a driver to make an informed decision about what to do in the event the "warning" pops up. When you hear it "rumbling" you should have been off the freeway 2 minutes ago.