Flaky TPMS?

[Capsfan84]

Hi guys,

So first of all I did RTM, and I also did a search about the particular problem I was having with the system on my 2014 CX-5 Touring, and it does appear as though some other folks have had this issue. I just want to clarify whether or not we are talking about two separate system and if they are just confusing me.

Driving into work this morning I got a warning on my dashboard telling me that tire pressure was low, so after I got home from work I let the car sit for about 2 hours with the ambient temperature being around 45 or so and when I checked them all 4 tires were low, around 26psi or so. I brought them all back up to 34psi and hit the reset button to the left of the steering wheel. I thought that would fix the problem but even though the light flashed twice and the beep sounded the same error message popped up telling me that tire pressure was low.

Frustrated, I double checked all the tires and they were all right at 34, so I went into the maintenance menu remembering that I had the reminders set to remind me every 3 months to check the tire pressure. I still had about 12 days left according to the car before I needed to check pressure, but it seemed like some other people were getting the same error message with 10+ days left on the reminder. The warning only went away after I turned off the maintenance reminder and then turned it back on, resetting it to 3 months.

Bottom line, is the system screwy or was it just the reminder I had set myself? Seems odd that it would continue to tell me pressure was low even after I brought them all back up to 34psi.

 

[minnesotaart]

I thought you had to drive it a bit after the reset before it was "satisfied" with the pressure. But then again, I've never had the warning message, so no personal experience.

 

[flymo]

After you set the pressure to 34, and reset the TPMS system, when did the warning occur? You know the TPMS system doesn't have actual pressure sensors, right? So you need to drive around a bit before it can tell if your pressure is low or not.

By the way, 26 psi is dangerously low, to the point of compromising handling and braking. Since all 4 tires were low, that can only be because you hadn't checked the pressure in a looooong time. You need to rethink your schedule and check the tire pressure more often.

F

 

[Capsfan84]

After you set the pressure to 34, and reset the TPMS system, when did the warning occur? You know the TPMS system doesn't have actual pressure sensors, right? So you need to drive around a bit before it can tell if your pressure is low or not.

By the way, 26 psi is dangerously low, to the point of compromising handling and braking. Since all 4 tires were low, that can only be because you hadn't checked the pressure in a looooong time. You need to rethink your schedule and check the tire pressure more often.

F

I didn't drive around at all after resetting the TPMS, but at the same time the manual didn't indicate that it was necessary to do so in order to get the light turned off. I would have thought that they would include that if I needed to do it.

I agree that 26 is way too low, and that's all the more reason that I don't want to turn off the reminder in my car to check my tire pressure. I'm going to be more diligent about checking it in the future, even if I am still confused as to whether or not it was the actually sensor that tripped me up or if it was the periodic maintenance reminder that I had set.

 

[flymo]

I could argue it both ways - the reset should clear the light, or the light stays on until the system can learn the pressure is OK from counting the wheel rotations. Given that it is a safety issue, I would guess the design is to show the fault until the system knows there isn't one.

If that's the case, then yes, it would be nice if the manual said that.

Flymo

 

[nXt]

On my 2014 Touring with Tech, the reminder menu I set to 1 month, but it ALWAYS WARNS ME EVERY 15 DAYS. 15 DAYS. No idea why, but every 15 DAYS it tells me to check tire pressure. It's annoying. It's the same with mine, the reminder will still show, so you have to TURN OFF the reminder and turn it back on, or reset it back to 1 month. Then the message will go away.

 

[Capsfan84]

On my 2014 Touring with Tech, the reminder menu I set to 1 month, but it ALWAYS WARNS ME EVERY 15 DAYS. 15 DAYS. No idea why, but every 15 DAYS it tells me to check tire pressure. It's annoying. It's the same with mine, the reminder will still show, so you have to TURN OFF the reminder and turn it back on, or reset it back to 1 month. Then the message will go away.

Just for clarification, is your car telling you to check your tire pressure or is it telling you to increase your tire pressure? My car was definitely telling me to increase my tire pressure, even after I had inflated my tires to 34 psi. The reason I thought that it could be the reminder was because I know that other people were having the issue where the car would remind them 10 or 15 days ahead of when it is scheduled to do so.

 

[Beefy]

Just for clarification, is your car telling you to check your tire pressure or is it telling you to increase your tire pressure? My car was definitely telling me to increase my tire pressure, even after I had inflated my tires to 34 psi. The reason I thought that it could be the reminder was because I know that other people were having the issue where the car would remind them 10 or 15 days ahead of when it is scheduled to do so.

The TPMS doesn't know whether you need to increase or decrease pressure. It has no measure of absolute pressure, only if one wheel is different. If all of your tires were exactly 26 PSI, it would not work. If all of your tyres were exactly 10 PSI, it would not work. But one tire 26 when the other three are 34 would absolutely be detected.

 

[i3enny]

I find this post interesting.... My wife has a 2015 Mazda6 and she just got a recall/NHTSA notice on her TPMS...

 

[Dr. Awkward]

From NHTSA:
Mazda North American Operations (Mazda) is recalling certain model year 2014-2015 Mazda6 vehicles manufactured October 25, 2012, to October 10, 2014.
If the pressures of four of the tires on an affected vehicle gradually drop at the same time, the tire pressure monitoring system (TPMS) may not warn the driver of the drop in pressure. As such, these vehicles fail to comply with the requirements of the Federal Motor Vehicle Safety Standard (FMVSS) No. 138, "Tire Pressure Monitoring System."
A vehicle that is driven with under inflated tires may experience a sudden tire failure, increasing the risk of a crash.
Mazda will notify owners, and dealers will update the TPMS software, free of charge.
The recall began on December 10, 2014.
Owners may contact Mazda customer service at 1-800-222-5500.

 

[MikeM.]

Which begs the question: If all four tires gradually lose air at the same rate, how can any TPMS based on wheel speed sensors detect it unless the car is equipped with GPS?

 

[flymo]

Man, talk about a solution looking for a problem - although I guess you could argue that's the case for the existence of TPMS systems in the first place.

If TPMS is helpful at all, it's to warn you about a tire slowly losing air before it becomes obvious. It's not a replacement for checking your tire pressure (on all 4 tires) periodically.

Flymo

 

[jjw6455]

TPMS can take into account engine RPM. If the RPM increases for a set speed/gear, the wheel diameter decreased (all wheels lost air). Using running time, ordinary tire wear can be taken into account.

 

[MikeM.]

TPMS can take into account engine RPM. If the RPM increases for a set speed/gear, the wheel diameter decreased (all wheels lost air). Using running time, ordinary tire wear can be taken into account.

Please put your thinking cap on and strap it on snugly because I don't want this simple concept to turn into an irrational debate.

The concept that "If the RPM increases for a set speed/gear, the wheel diameter decreased" is not true for the following reason:

Vehicle speed is determined by the number of wheel rotations per unit of time multiplied by the diameter of the tire. Therefore, if the tire diameter changes (as it will with air loss) then the calculated speed will still be the same for any given rpm/gear (because it has no way to know the diameter has changed).


The only way a system using wheel speed sensors could detect gradual air loss of all four tires simultaneously is if the vehicle had a way to determine vehicle speed that was entirely independent of tire diameter. GPS could be used but I was under the impression that not all CX-5's were equipped with GPS receivers (although it is possible they are, maybe cars without GPS option still have internal GPS's).

 

[nXt]

Just for clarification, is your car telling you to check your tire pressure or is it telling you to increase your tire pressure? My car was definitely telling me to increase my tire pressure, even after I had inflated my tires to 34 psi. The reason I thought that it could be the reminder was because I know that other people were having the issue where the car would remind them 10 or 15 days ahead of when it is scheduled to do so.

Got in my CX-5 yesterday morning and it told me to INCREASE tire pressure. I go check all the tires and all of them were 34PSI except 1 which was at 35/36.
I go back inside to check the Maintenance Message, and there was 15 days left of the 1 month Tire Pressure Check reminder. So like clockwork, every 15 days it tells me to INCREASE tire pressure, not Check tire pressure.

 

[piotrek91]

The only way a system using wheel speed sensors could detect gradual air loss of all four tires simultaneously is if the vehicle had a way to determine vehicle speed that was entirely independent of tire diameter. GPS could be used but I was under the impression that not all CX-5's were equipped with GPS receivers (although it is possible they are, maybe cars without GPS option still have internal GPS's).

The only "software" fix I can think of here is for the car to monitor ambient temperature and also to use a set time interval for warning the driver.

The system could remember the ambient temp when the system was last reset and if the low temp of the day drops, say 20 degrees below that, it could set off a warning. Additionally to combat slow leakage of air it could issue a warning at set intervals.

I can see such a software fix leading to even more threads from users having trouble figuring out why the TPMS light turned on

 

[Capsfan84]

Got in my CX-5 yesterday morning and it told me to INCREASE tire pressure. I go check all the tires and all of them were 34PSI except 1 which was at 35/36.
I go back inside to check the Maintenance Message, and there was 15 days left of the 1 month Tire Pressure Check reminder. So like clockwork, every 15 days it tells me to INCREASE tire pressure, not Check tire pressure.

Thank you for that! Sounds like I'm not the only one getting the INCREASE tire pressure message at around 15 days before my scheduled reminder. Either way I'm glad I have it because I should have never let my tires get that low anyway.