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[bchcky]

I hope this is the right section for this. I'm wondering how finicky the TPMS usually is? I drive an '07 328xi. All 4 tires are relatively new. In the past few months, I've gotten a warning light about tire pressure. Typically it had been one of the back two, I brought the vehicle to the local tire shop to have them plugged and/or looked at, all good there.

Now the other day, I get in, same error because I hadn't filled up the rear left, but now it's ALL FOUR tires that are "low." Now I put low in quotes because I tested each tire, and off the top of my head, the rears were at 33 and 35, and the front were at 29 and 31 I believe with the vehicle calling for 36 in the rear, and 32 in the front.

Obviously the TPMS is accurate, since none of the tires were what is recommended. But do other people have a problem with say... weather affecting the TPMS? On Monday this week it was about 55 degrees out, today it's in the 80's. During this time of year in West Texas the weather can fluctuate a lot. Any other ideas? Just for reference, I've probably had the warning for each rear tire 2 times in the last few months. Each time it was 1-3 lbs below the pressure recommended, each time I filled them, and it went away. I am completely open to the idea that it is just the tires, and might be time to buy new ones, but I'm just wondering first if anyone else notices that their TPMS might be hyper-sensitive?

Thanks in advance.

[ceb]

Originally Posted by bchcky

I hope this is the right section for this. I'm wondering how finicky the TPMS usually is? I drive an '07 328xi. All 4 tires are relatively new. In the past few months, I've gotten a warning light about tire pressure. Typically it had been one of the back two, I brought the vehicle to the local tire shop to have them plugged and/or looked at, all good there.

Now the other day, I get in, same error because I hadn't filled up the rear left, but now it's ALL FOUR tires that are "low." Now I put low in quotes because I tested each tire, and off the top of my head, the rears were at 33 and 35, and the front were at 29 and 31 I believe with the vehicle calling for 36 in the rear, and 32 in the front.

Obviously the TPMS is accurate, since none of the tires were what is recommended. But do other people have a problem with say... weather affecting the TPMS? On Monday this week it was about 55 degrees out, today it's in the 80's. During this time of year in West Texas the weather can fluctuate a lot. Any other ideas? Just for reference, I've probably had the warning for each rear tire 2 times in the last few months. Each time it was 1-3 lbs below the pressure recommended, each time I filled them, and it went away. I am completely open to the idea that it is just the tires, and might be time to buy new ones, but I'm just wondering first if anyone else notices that their TPMS might be hyper-sensitive?

Thanks in advance.

A few facts:

A ten degree drop in temps is equal to a psi drop in pressure.
A good tire uses about one psi per month
TPMS sensors are required to alert at 25% below the set value

So, the question is "what was the system set to?"

Here's what you need to do.

Fill the tires to the proper pressure. Reset the system. Check the tires in a week.

I'll bet you never reset the system and that is what is causing your alerts.

[bchcky]

Hmm... OK. Previously, when just one tire would be low, the system had reset itself every time. I filled it with the vehicle running once and by the time I was back in my car, the system had reset and all the tires on the screen were back to green (w/iDrive the tires that are low show up as orange).

I'm going to fill them all in the morning to the correct pressure and reset the system. We'll see where we go from there. Hopefully I don't get any errors too soon after. It gets really tedious with the error light on.

[cole92]

Yup, this morning had a LTP warning since it's now snowing here. 35 degree weather. Check the psi with a guage and they were still within normal. I just reset the system to adjust for the weather.

[Tom K.]

Originally Posted by bchcky

Hmm... OK. Previously, when just one tire would be low, the system had reset itself every time. I filled it with the vehicle running once and by the time I was back in my car, the system had reset and all the tires on the screen were back to green (w/iDrive the tires that are low show up as orange).

I'm going to fill them all in the morning to the correct pressure and reset the system. We'll see where we go from there. Hopefully I don't get any errors too soon after. It gets really tedious with the error light on.

I'm not understanding your statement that "the system had reset". The system does not reset, it simply no longer had the low tire pressure present so the warning light went off. It compares the pressures to the "baseline" pressures when the system was last reset.

So what ceb meant was that after filling all 4 tires to the proper cold pressure, you must do the system reset which is explained in your owner's manual (page 92 in the online '07 version). Then, you will have a new baseline and should only get a warning when a tire drops at least 25% below that baseline.

Tom