# Low tire pressure sensor



## DeanHensler (Jul 2, 2012)

I am getting a low tire pressure light and my 2012 Cruze LT thinks that the RF, RR and LR tires are low (28lbs of pressure). I have filled them up to 35 lbs and the low tire pressure light is still on. Anyone else having problems with this? It seemed to happen after the first day of cold weather in Missouri and has not gone away for a month.

I'm on my 2nd set of tires and the car has around 70k miles on it. The new tires were put on over a year ago.


----------



## ChevyGuy (Dec 13, 2014)

DeanHensler said:


> I have filled them up to 35 lbs and the low tire pressure light is still on.


How far have you driven since the fill up? The display is not real-time.

The other thought is to check what's supposed to happen when the batteries get low. A low battery will get worse in the cold. It's probably a light and code of some kind, possibly confused with "low pressure".


----------



## Robby (Mar 1, 2013)

You mean the lights been on for a month after you aired the tires, or the lights been on a month and you aired the tires today with no change?
BTW....you loose 1 psi for every 7 degree drop in temperature (slightly variable...rubber tire) as well as natural loss from time.....that's why you should get in the habit of checking monthly.

If your light stays on for hours after airing up you should first have the sensors 'Relearned' by your dealer or tire store.....usually a "no charge' service......this proceedure forces the moniters to 'Wake up' and report.

Rob


----------



## Robby (Mar 1, 2013)

When the monitor fails, either electronically or from its internal battery dieing, the Cruze will display 'Service TPMS' and the low tire lamp will illuminate.
If you scroll to the tire readout, the non functioning monitor will be shown as a line of dashes with no readout at that wheel position.

Rob


----------



## LiveTrash (May 24, 2015)

Robby said:


> When the monitor fails, either electronically or from its internal battery dieing, the Cruze will display 'Service TPMS' and the low tire lamp will illuminate.
> If you scroll to the tire readout, the non functioning monitor will be shown as a line of dashes with no readout at that wheel position.
> 
> Rob


It should also be noted that if you rotated your tires, the sensor reading on the dash may not correspond with the malfunctioning wheel sensor if they were not programmed to their new position.


----------



## Robby (Mar 1, 2013)

LiveTrash said:


> It should also be noted that if you rotated your tires, the sensor reading on the dash may not correspond with the malfunctioning wheel sensor if they were not programmed to their new position.


That would be 'WILL' not correspond.....gotta gotta gotta relearn GM systems.

Rob


----------



## DeanHensler (Jul 2, 2012)

I haven't rotated the tires and it has been months since the warning came on and I checked tire pressure. Is there any way to make the sensors "re-learn" without taking it to the dealership or tire store? I would much rather do it myself if no special tools are required.


----------



## obermd (Mar 3, 2012)

If the sensors are in the correct position letting air out and then reinflating the tire should trigger a pressure update.


----------



## roadrunnerA12 (Jan 21, 2015)

Tires lose (or gain) 2% of their pressure for every 10F change in temp. (Not 1 psi for every 7F change). So, starting at 35 psig, a 10F drop in temp. results in 0.7 psig drop. The typical average temp. difference between summer and winter is 50F. So from Summer average temp. and 35 psig pressure in the tires, a drop of 50F to average winter temp. would result in a 3.5 psig pressure drop (assuming no leakage). So winter average temp pressure would be 31.5 psig if I do nothng. If all four tires have no leakage (beyond the occassional molecule or two of air escaping thru the valve and beads), the TPM system would not activate from normal temperature change of average summer temp to average winter temp. I believe that most TPM systems trigger the light if any one tire becomes 5 psig lower than the other three. But these systems may also put the light on if all four tires get well below the recommended pressure???


----------



## obermd (Mar 3, 2012)

roadrunnerA12 said:


> Tires lose (or gain) 2% of their pressure for every 10F change in temp. (Not 1 psi for every 7F change). So, starting at 35 psig, a 10F drop in temp. results in 0.7 psig drop. The typical average temp. difference between summer and winter is 50F. So from Summer average temp. and 35 psig pressure in the tires, a drop of 50F to average winter temp. would result in a 3.5 psig pressure drop (assuming no leakage). So winter average temp pressure would be 31.5 psig if I do nothng. If all four tires have no leakage (beyond the occassional molecule or two of air escaping thru the valve and beads), the TPM system would not activate from normal temperature change of average summer temp to average winter temp. I believe that most TPM systems trigger the light if any one tire becomes 5 psig lower than the other three. But these systems may also put the light on if all four tires get well below the recommended pressure???


I see closer to a 10-12% drop from a smaller temperature change. OP, have you checked your tire pressure with a good tire pressure gauge when your TPMS is showing 28 or lower PSI?


----------



## roadrunnerA12 (Jan 21, 2015)

So let's use your numbers instead of Robby's. You say that you lose 10% of your tire pressure every "less than 10 degrees F temp drop." Let's use "every 7 degrees" (which is what Robby used in his "rule of thumb.") Let's start at 35 psig and 70F temp. What you are saying is that at 63F, your pressure is down to 31.5. Then at 56F, your pressure is down to 28.35 (round to 28.4), then at 49F, you are down to 25.6. At 42F, you are down to 23 psig. Next comes 35F and you are down to 20.7 psig. The next chilly morning, the temp is 28F and your pressure is down to 18.5. It gets even colder over night and your temp is now 21F, where I end this saga. Your pressure is now 16.6 psig. Is this what you have actually observed? There is no "rule of thumb" involved with what actually happens, just the Gas Laws, of which I am schooled.


----------



## obermd (Mar 3, 2012)

My pressure drop isn't linear. The first 10 degrees are the biggest and then it slows down. However, you didn't answer my question - have you checked your tire pressure with a good gauge? TPMS has been known to be off, and sometimes by as much as 5 PSI. (I had one that was high by 4 PSI).


----------



## Eddy Cruze (Jan 10, 2014)

obermd said:


> My pressure drop isn't linear. The first 10 degrees are the biggest and then it slows down. However, you didn't answer my question - have you checked your tire pressure with a good gauge? TPMS has been known to be off, and sometimes by as much as 5 PSI. (I had one that was high by 4 PSI).


 Mine are off by around 6 to 8 PSI. I even get monthly warnings from OnStar, however I now know the only way to accurately check pressure is by not using the TPMS feature


----------



## jblackburn (Apr 14, 2012)

Eddy Cruze said:


> Mine are off by around 6 to 8 PSI. I even get monthly warnings from OnStar, however I now know the only way to accurately check pressure is by not using the TPMS feature


Are you sure that the tire gauge you're using to check is accurate? Mine are 1-2 psi off at most.


----------



## Eddy Cruze (Jan 10, 2014)

jblackburn said:


> Are you sure that the tire gauge you're using to check is accurate? Mine are 1-2 psi off at most.


 Yes which is surprising as I actually had close to 45 psi when the sensors read 37. After two shops confirmed this I checked myself with a new gauge and had to adjust them down. My free air connection is getting tired of seeing me.


----------



## spacedout (Dec 7, 2010)

jblackburn said:


> Are you sure that the tire gauge you're using to check is accurate? Mine are 1-2 psi off at most.



One of the gas stations here has a new fancy digital air pump you set the pressure, set it right at 38psi and the DIC reads on every single wheel right at 38psi when I drive away. Checked with a gauge they all read 38PSI, guess I'm lucky mines so accurate. 

If people are seeing such a huge discrepancy, I wonder if they filled cold and tested hot?


----------



## Eddy Cruze (Jan 10, 2014)

jblackburn said:


> Are you sure that the tire gauge you're using to check is accurate? Mine are 1-2 psi off at most.


 I just checked again. While I'm sure the sensors are off, I am positive I need more air, it is cold here (64F) and all tires read around 32


----------



## jblackburn (Apr 14, 2012)

spacedout said:


> One of the gas stations here has a new fancy digital air pump you set the pressure, set it right at 38psi and the DIC reads on every single wheel right at 38psi when I drive away. Checked with a gauge they all read 38PSI, guess I'm lucky mines so accurate.
> 
> If people are seeing such a huge discrepancy, I wonder if they filled cold and tested hot?


My Craftsmen tire pump does that! But both it and my gauge and agree that the car is very slightly off.


----------



## au201 (May 18, 2013)

spacedout said:


> One of the gas stations here has a new fancy digital air pump you set the pressure, set it right at 38psi and the DIC reads on every single wheel right at 38psi when I drive away. Checked with a gauge they all read 38PSI, guess I'm lucky mines so accurate.
> 
> If people are seeing such a huge discrepancy, I wonder if they filled cold and tested hot?


The gas station near me has that newfangled thing too! My Cruze also agrees perfectly with that every time. Tested with real gauge was exactly the same too. Set to 43...got 43


Sent from AutoGuide.com Free App


----------



## spacedout (Dec 7, 2010)

au201 said:


> The gas station near me has that newfangled thing too! My Cruze also agrees perfectly with that every time. Tested with real gauge was exactly the same too. Set to 43...got 43


I really like these new machines, the ones around here are free too. Allot of stations you have to pay a dollar for air and run around like nascar to make sure it doesn't shut off before your finished. 

Allot of the free ones I find are missing either the end off the hose or the entire hose, guess when their is no profit margin there is no reason to fix things.


----------



## NickD (Dec 10, 2011)

Air pressures are based on absolute zero that really cuts down this numerical ratio. About the most you will see going from 0* to 100*F temperature variation is about 6 PSI worth of difference.

Tire pressure like your coolant level should only be checked when cold. When I took off a couple of years ago in -27*F weather, was reading 28 psi on all four tires, after 50 miles or so, all four were at 35 psi.

Heat in your home is also based on absolute zero, so by dropping your thermostat from 72 to 68*F, doesn't even make a dent in your heating bill, but sure helps mold build up. But you are not told this by the idiots that run our government. If they had any brains at all, would be working in private industry. 

I was rejected from getting a government job because my IQ was greater than 2!


----------



## obermd (Mar 3, 2012)

NickD said:


> Heat in your home is also based on absolute zero, so by dropping your thermostat from 72 to 68*F, doesn't even make a dent in your heating bill, but sure helps mold build up. But you are not told this by the idiots that run our government. If they had any brains at all, would be working in private industry.


False - heating and cooling needs are based on the relative heat difference between the inside and outside. If it's 68 outside and you drop your heat from 72 to 68 you eliminate the need to heat your home. Likewise if it's 80 outside and you raise your cooling point to 80 you eliminate the need to cool your home.


----------



## ChevyGuy (Dec 13, 2014)

Heat flow is an equation like ohm's law. The temperature differential is like voltage. Heat is like current. Insulation is like resistance. 

The greater the temperature difference between inside and outside, the more heat will flow though the insulation.


----------

