Did the TPMS always tell you which tire is low?

My 2008 MT 328i (E92) has never shown which tire is low, which is a nuisance when a wheel cracks and the air starts to leak out. I would have assumed that BMW doesn't like to use corner-specific TPMS because there isn't a reliable way for the car to "know" which sender is in which corner, if for example someone rotated the tires.

Originally Posted by raleedy

My 2008 MT 328i (E92) has never shown which tire is low, which is a nuisance when a wheel cracks and the air starts to leak out. I would have assumed that BMW doesn't like to use corner-specific TPMS because there isn't a reliable way for the car to "know" which sender is in which corner, if for example someone rotated the tires.

I believe (note "believe", not "know") that the sensors are low power transmitters requiring a receiver at each wheel, so that the car knows where each signal originates.

Originally Posted by Zooks527

I believe (note "believe", not "know") that the sensors are low power transmitters requiring a receiver at each wheel, so that the car knows where each signal originates.

This is correct. The BMW has 4 receivers at each wheel. This is the reason we can simply hit a button an learn our new sensors (winter wheels for example). On my Infiniti, and Subaru, it meant taking the car to the dealer so that the car could be "programmed" with the serial number for each wheel. Those cars have one receiver. Makes changing over you winter wheels perfect, as compared to driving around with the light on all winter

Originally Posted by mossman35

This is correct. The BMW has 4 receivers, one at each wheel. This is the reason we can simply hit a button an learn our new sensors (winter wheels for example). On my Infiniti, and Subaru, it meant taking the car to the dealer so that the car could be "programmed" with the serial number for each wheel. Those cars have one receiver. Makes changing over you winter wheels perfect, as compared to driving around with the light on all winter

Fixed for clarity.


BMW's system is best. Here's what happens on some of the competition. As you said, there is a code sent by each monitor identifying which one it is, and therefore which tire location is sending the signal. If the tires are rotated the signal will still identify the same tire but now it is at a different position.
Had a customer who kept getting a "Right rear tire low" notification. She kept adding air but the notice stayed on. It turned out to be the left front which was low, the shop which rotated the tires did not run the reset procedure. It can be lengthy, and it requires some special tooling to identify the monitors' code numbers (hexidecimal!)

Originally Posted by DSXMachina

Fixed for clarity.

Thanks. Makes much more clear now. I knew what I meant to say....

Originally Posted by mossman35

Thanks. Makes much more clear now. I knew what I meant to say....

I knew you did, and I knew what you meant But some noob was going to search the subject and think that we have 16 receivers on our cars.

The statement that somehow the car would lose the intelligence about sensor locations if the tires are rotated is simply NOT true.

Any car I had with sensors (Jeep, Infinity) - would automatically re-learn the sensor location in a few minutes (including after rotation using full size Spare).

To say that BMW system is "The best" because it does not provide the information that "may be confusing to the driver" can only come from BMW.

I hope hat there is enough push back from the customers to make BMW change the system to become usable.

Originally Posted by vlad7777

The statement that somehow the car would lose the intelligence about sensor locations if the tires are rotated is simply NOT true.

Any car I had with sensors (Jeep, Infinity) - would automatically re-learn the sensor location in a few minutes (including after rotation using full size Spare).

Long answer:
We were speaking in reference to having two sets of sensors (winter and summer) as some people have. The Infiniti (you would think you would spell it correct if you had one ) absolutely does not re-learn a thing unless you bring it to the dealer. If you simply swap tire locations it will not know they were swapped. In other words it will still think the right front is on the right front even if you have moved it. It's a moot point because the Infiniti (the G35 I had at least) didn't tell which tire was low. It simply turned on a light indicating a given tire is low. So if they are swapped, who cares. If you put new sensors on and didn't re-program you have to go to the Infiniti dealer.

Short answer:
What you said is not correct. The Infiniti (like most) has one receiver to sense all 4 sensors. It has no clue about location, it simply knows the sensors are close by.

Originally Posted by mossman35

Long answer:
We were speaking in reference to having two sets of sensors (winter and summer) as some people have. The Infiniti (you would think you would spell it correct if you had one ) absolutely does not re-learn a thing unless you bring it to the dealer. If you simply swap tire locations it will not know they were swapped. In other words it will still think the right front is on the right front even if you have moved it. It's a moot point because the Infiniti (the G35 I had at least) didn't tell which tire was low. It simply turned on a light indicating a given tire is low. So if they are swapped, who cares. If you put new sensors on and didn't re-program you have to go to the Infiniti dealer.

Short answer:
What you said is not correct. The Infiniti (like most) has one receiver to sense all 4 sensors. It has no clue about location, it simply knows the sensors are close by.

Why should a vehicle have to re-learn which sensor is which when tires are changed? Does the receiver in the wheel well need to be uniquely paired with the sensor in the wheel?

Originally Posted by sunny5280

Why should a vehicle have to re-learn which sensor is which when tires are changed? Does the receiver in the wheel well need to be uniquely paired with the sensor in the wheel?

Since you asked about "receiver in each wheel well" I'll assume you are asking about our vehicles. I believe the only reason it needs to know what sensor is which is to distinguish which tire is low or flat. Although, I believe our cars also use rotational speed sensors (same as ABS I think) that can detect a low tire by rotational speed. As most probably know, this is another method to detect low air pressure and does not need internal sensors. I am still unclear as to if our vehicles use both methods or just one to determine low air pressure or a flat tire.

I know this thread mostly talks about the ability for our cars to tell which tire is low. My car still clearly shows which of the 4 tires is low. It went off just a few weeks ago. Not sure if that is the case on all firmware updates and all model years.

Originally Posted by sunny5280

Why should a vehicle have to re-learn which sensor is which when tires are changed? Does the receiver in the wheel well need to be uniquely paired with the sensor in the wheel?

Did you mean tires or wheels? I was referring to a second set of winter wheels and tires (with different sensors) that I swap on myself Then the vehicle needs to learn those sensors.

Originally Posted by mossman35

Since you asked about "receiver in each wheel well" I'll assume you are asking about our vehicles. I believe the only reason it needs to know what sensor is which is to distinguish which tire is low or flat. Although, I believe our cars also use rotational speed sensors (same as ABS I think) that can detect a low tire by rotational speed. As most probably know, this is another method to detect low air pressure and does not need internal sensors. I am still unclear as to if our vehicles use both methods or just one to determine low air pressure or a flat tire.

While my focus is on BMW's the question is applicable to all vehicles.

As for knowing which tire is low or flat I see no reason the vehicle couldn't determine this based on the information being fed to it by each individual receiver. I.e. if the front passenger receiver is sending a tire pressure of 28 PSI (assuming 28 PSI is out of specification) then the system can, based on the passenger receiver sending the 28 PSI pressure, alert the driver the front passenger tire is low. I see no reason for the system to require the sensor in the tire be paired with the receiver.

Originally Posted by sunny5280

While my focus is on BMW's the question is applicable to all vehicles.

As for knowing which tire is low or flat I see no reason the vehicle couldn't determine this based on the information being fed to it by each individual receiver. I.e. if the front passenger receiver is sending a tire pressure of 28 PSI (assuming 28 PSI is out of specification) then the system can, based on the passenger receiver sending the 28 PSI pressure, alert the driver the front passenger tire is low. I see no reason for the system to require the sensor in the tire be paired with the receiver.

With 4 receivers, yes. With one receiver no. How does one receiver know where each sensor is located? Are you thinking signal strength at 4 corners? I would hazard an educated guess that would be rather messy and overly complicated to determine location based on those distances but I didn't design the system. FYI, my career is wireless engineering so it's a pretty good educated guess.

So, for one receiver systems, the simplest means is to tell the receiver which sensor serial number to associate with which corner of the vehicle. This is why Infiniti wanted to charge me $60 to walk around the car and read each sensor serial number (with a tool) and program the receiver. That would be $60 twice a year when I swap tires. I lived with the warning light all winter instead.

The BMW has 4 receivers, so it works as you are saying. It's much easier to detect location at a much closer distance. Although, now that you mention it, I never tired swapping wheels without doing a reset. There's probably a good chance it might simply start reading the new sensors on the new wheels. My pressures are always different (summer staggered wheels versus 17" same size). I always reset when I swap tires for this reason alone. Perhaps if you had same size tires, same temperature, same pressures it would just work. Still would make sense to reset because the odds that is all going to line up is small.

Originally Posted by mossman35

With 4 receivers, yes. With one receiver no. How does one receiver know where each sensor is located? Are you thinking signal strength at 4 corners? I would hazard an educated guess that would be rather messy and overly complicated to determine location based on those distances but I didn't design the system. FYI, my career is wireless engineering so it's a pretty good educated guess.

Yes, signal strength doesn't need to be very high in order for the receiver to read the sensor.

Originally Posted by DSXMachina

Your monitors broadcast psi to the tenth of a pound. You'd think on a vehicle in that price range it would display actual pressure. Like some cars for 1/2 the cost.

You'd think it would automatically honk when I get the tire pressure up to spec.

Originally Posted by hellosopo

You'd think it would automatically honk when I get the tire pressure up to spec.

When your wheel is not turning, the TPMS is (usually) not transmitting. This is why it is necessary to drive the car some (short) distance after a tire pressure re-set. By explanation:

What tells the sensors to transmit when they are on the road? The answer is accelerometers and programming that tells the sensor to transmit at specific intervals and speeds. When a sensor is not turning, it is not typically transmitting information. When it is moving, it is transmitting information in 15, 30 or 60 second intervals depending on the application. By not transmitting a signal all the time, the battery can last up to 10 years.

When a vehicle is not moving for a defined period of time, the sensors will go into a rest or sleep mode. It may take between 10 to 20 minutes for the sensor to enter this mode. Some systems (*) require the sensors to be in this mode when the relearn procedure is initiated. This is why some systems require the vehicle to sit for at least 20 minutes.
(*) not sure if this applies to our BERU systems.