Low tire air pressure indicator

Hello there:

The temperature dropped to mid 30s this weekend. Took a short drive to the store and when I turned the car back to come home noticed the dash indicator for low tire pressure blinking and then steady. Checked the tires, all looked good and started to drive then I pressed the reset buttom in the light went off.

Should I be worried?

Thanks

Figman

Define "they all looked good". Appearance of tyre is not a good way to tell if you need air. Tomorrow morning when it's still cold, take a tyre pressure gauge and check that they are all inflated properly to approx 2,3-2,4 bar or about 33 psi.

Definitely check the air pressure ASAP. I've read a tire can loose as much as 10lbs of pressure before they activate. I know first hand that loosing 3 lbs. won't activate them. An under or over-inflated tire is subject to becoming damaged and affect vehicle safety. Check your pressure regularly, especially when large outside temperature swings occur. either up or down. Your most accurate measurements occur after the vehicle has been sitting for a few hours, some manufacturers say as much as 7, or when it's been driven cold for less than 2 miles at low to moderate speeds.

Sorry for the dissertation.

This is definitely a case of RTFM.

This is a feature that may vary between years for starters. In some versions of TPM they use the ABS brake sensors to compare subtle variations in rotational speed of the tires to detect one that is rolling just a bit faster than it should. This would indicate a smaller rolling circumference caused by low tire pressure. Other versions of TPM will actually use battery powered sensor modules in each wheel (I think the theory is that replace the batteries when you replace the tires).

You have one indicator light and it can be flashing or constant. It can also be yellow or red. Each of these conditions provides a different message and warrants a different response.

If the indicator is red, that is the most serious issue and warrants immediate check of tire pressures.
If the indicator is yellow IIRC it only means that one of the sensors did not report in. It is more of a system fault than a tire fault.

The manual explains it all.

Originally Posted by figman

Hello there:

The temperature dropped to mid 30s this weekend. Took a short drive to the store and when I turned the car back to come home noticed the dash indicator for low tire pressure blinking and then steady. Checked the tires, all looked good and started to drive then I pressed the reset buttom in the light went off.

Should I be worried?

Thanks

Figman

If your tires were still pretty cold at the store then maybe they are just on the edge of being under inflated. They lose pressure in cold weather. If the trip to the store was a couple of miles away maybe they were hot enough when you checked them so they registered as ok when they are underinflated.

From what I understand, if you reset the TP indicator when they are still under inflated then you have reset them for a new, lower normal. If they are fine, maybe it is an electrical malfunction of the indicator.

If it registers RED then it is time to call your trusty BMW roadside assistance.

Originally Posted by PPXYZ

If your tires were still pretty cold at the store then maybe they are just on the edge of being under inflated. They lose pressure in cold weather. If the trip to the store was a couple of miles away maybe they were hot enough when you checked them so they registered as ok when they are underinflated.

From what I understand, if you reset the TP indicator when they are still under inflated then you have reset them for a new, lower normal. If they are fine, maybe it is an electrical malfunction of the indicator.

Exactly right.

dj

If they are giving "false" errors due to temp changes a work around may be to set the indicator with tire pressure at say 30 lbs then inflate tires to 33 or 34. That way then when pressure drops due to change in external temp the low pressure indicator is not activated. However, if a truly significant drop in pressure occurs the sensor still will alert you. Will this work??

Hello there:

I checked the air pressure the next morning and three tires were at 29PSI one was at 28PSI. I checked the door label and it says front 29 rear 32; is this the common practice or you advice otherwise?

Thanks again

Figman

Originally Posted by figman

Hello there:

I checked the air pressure the next morning and three tires were at 29PSI one was at 28PSI. I checked the door label and it says front 29 rear 32; is this the common practice or you advice otherwise?

Thanks again

Figman

I would raise them all up to 32 psi evenly. There's really no need for the understeer.