Tire Pressure Warning, But Which Tire?!

[Butcher]

I've looked through the owners manual but i don't see any indication that the warning system will identify which tire is low. Can this be right? Since there are sensor's in each tire it must KNOW which one is low but i can't tell how. Can anyone confirm this is the way it works or tell me what i'm missing.

Thx

07, IS350, with ML+Nav+bluetooth

[tex2670]

I've looked through the owners manual but i don't see any indication that the warning system will identify which tire is low. Can this be right? Since there are sensor's in each tire it must KNOW which one is low but i can't tell how. Can anyone confirm this is the way it works or tell me what i'm missing.

Thx

07, IS350, with ML+Nav+bluetooth

It doesn't tell you which. You need to carry a tire guage in the car, as it's hard to just look at the tires to see it's flat since they have a low profile.

[Butcher]

I've looked through the owners manual but i don't see any indication that the warning system will identify which tire is low. Can this be right? Since there are sensor's in each tire it must KNOW which one is low but i can't tell how. Can anyone confirm this is the way it works or tell me what i'm missing.

Thx

07, IS350, with ML+Nav+bluetooth

It doesn't tell you which. You need to carry a tire guage in the car, as it's hard to just look at the tires to see it's flat since they have a low profile.

I had come to a similar conclusion, but i have to say, that seems retarded that there is a system in place to monitor pressure in each tire but this system cannot identify the tire which is low, even though it MUST know. Oh well

Thanks for the response.

[gordonw]

I believe the system does know, as each tire sensor has unique identifier codes, but without the proper scan tool, you won't be able to tell.

[Vegas]

My 'Z' identifies the wheel having a problem, but it would be foolish to check only that one.

If enough time has passed so that one tire is low, you would be prudent to check them all.

Consider the warning a notice to check all tires.

[Sidney07]

Perhaps this has eluded Lexus in it's "pusuit of perfection"?

Several other cars with tire pressure monitoring systems tell you which tire is low. It only makes sense.

Looked all over the manual. I must just be missing it, right? Or do I really have to check every single tire?

[bartkat]

Perhaps this has eluded Lexus in it's "pusuit of perfection"?

Several other cars with tire pressure monitoring systems tell you which tire is low. It only makes sense.

Looked all over the manual. I must just be missing it, right? Or do I really have to check every single tire?

You need to check your tires on a regular basis anyway as the warning system doesn't activate until there is at least a 4 PSI loss. Listen to Mario on the Firestone commercial.

[GDixon]

Don't forget to check the spare, too. It is monitored (at least in the RX).

[Butcher]

Don't forget to check the spare, too. It is monitored (at least in the RX).

Really? Hmm, well whether it's monitored or not that IS a good reminder, i don't think i've EVER checked the pressure on a spare.

One last comment tho, every other time pressure monitoring system i saw on other manufacturers car's could visually indicate the pressure on each of the tires and could presumably tell you which tire might need more pressure. All the comments indicating the various reasons why you should check all the tires in the event of a low pressure warning are surely correct, i'm sure i should check more often. My point which i might now have made clearly is that the system must know WHICH tire is low and it seems like an obvious implementation of the system would be identification of the tire/sensor which has exceeded the threshold.

Thats all, and thanks for all the replies!

[tex2670]

Don't forget to check the spare, too. It is monitored (at least in the RX).

I don't believe that's the case for the IS.

[bartkat]

The 2nd generation IS has a high pressure compact tire and wheel, temporary spare. It's not monitored. However it should be checked occassionally as set forth in the owners manual.

[jrobsea]

I've been looking into snow tires and learned some things about the tire pressure monitoring system.

Each wheel (except the spare) has a battery powered pressure monitor on the valve stem inside the tire. The monitors each have a unique code. A radio receiver listens to the transmissions from the sensors in the wheels, and it lights up the indicator on the dash if pressure is too low.

The car knows which sensor code has low pressure, but I don't think it knows which wheel the particular sensor is installed in.

The IS supports two sets of sensors. There is supposed to be a switch somewhere that you can select which set of wheels are on the car. This way you can have a 2nd set of wheels/tires/sensors, and you can swap out winter tires without having to remount them on the factory rims.

Configuring a 2nd set of sensors requires the Lexus/Toyota specific software scan unit. I don't think there is a way around having a dealer service tech configure it. If you go to a tire shop and get the whole setup of wheels/snow tires/pressure monitoring sensors, you'll probably have to go to the dealer and pay some ridiculous charge to get them to enter the ID codes for your 2nd set of sensors.

I read in some tech info that the batteries last about 10 years. So if you're getting a new set of tires around 2015, and if you remember this, you might want to put some new batteries in the sensors while the tire shop is mounting the new tire set.

[Manolo1]

"The car knows which sensor code has low pressure, but I don't think it knows which wheel the particular sensor is installed in."

I just rotated my tires switching rims, there is no way any sensor can know which tire is low after you do that.

How can the "Z" tell you which tire is low?

fn: of course I also rotated the tires within the rims and switched rims to the opposite side

[Vegas]

All I know is that when the alarm goes off in my 2003 "Z", the warning show up on the cluster as 'left front' or 'right front' and the same with the rear wheels. In addition -- it also shows the real time psi for each wheel displayed.

Hell, if Nissan can do it, I'm sure that Lexus could also.

I never did rotate the tires, since the fronts are P225/45WR18, and the rear are P245/45WR18.

Still, when I go to get air, I check all four tires.

[Knightshade]

All I know is that when the alarm goes off in my 2003 "Z", the warning show up on the cluster as 'left front' or 'right front' and the same with the rear wheels. In addition -- it also shows the real time psi for each wheel displayed.

Hell, if Nissan can do it, I'm sure that Lexus could also.

I never did rotate the tires, since the fronts are P225/45WR18, and the rear are P245/45WR18.

Still, when I go to get air, I check all four tires.

For that matter Cadillac has offered that. For at least several years now. I had a rental DTS like 2 years ago that told you the pressure in each tire from the dash.

[Gaugster]

Chrysler has had individual pressure readings on there vehicles as well. Basically this represents two approaches for the automaker.

The Toyota system only reports that "a" tire is low. This will force the user to check all of the tires for correct pressure. This is a better method and a more conservative system with regard to safety. I would guess that Toyota wants to try to make sure that all of the tires are checked periodically and keep people from being lazy.

The other systems that report individual tire pressure may seem impressive but they also allow the user to only check the pressure of the suspect tire. This makes it possible to not check the other tires which could also be getting low but have not yet triggered a warning. This type of system is more complex and generally less reliable.

Both systems work well but usually only report an error when a tire is way low. The hope is to avoid nuisance warnings etc… It is just the Automaker’s mindset that determines how they want the electronics to interface with the human user. It’s a HMI thing.

Regards,

[Knightshade]

But if it displays pressure in each tire on the dash you can easily check all 4 tires. From your seat. Which one is a lot more likely to do on a very regular basis than if one has to manually check each tire.

Lazy people under the toyota system will completely ignore their tires till they get a warning. Under the GM/Chrysler system even lazy people can check all their tires at a glance/button push.

[jrobsea]

"The car knows which sensor code has low pressure, but I don't think it knows which wheel the particular sensor is installed in."

I just rotated my tires switching rims, there is no way any sensor can know which tire is low after you do that.

How can the "Z" tell you which tire is low?

fn: of course I also rotated the tires within the rims and switched rims to the opposite side

There is another way some cars detect low tire pressure. My Sienna minivan has 'indirect' TPMS. It doesn't use any pressure sensors in the wheels. It watches the rotational speed of each wheel. If pressure is low in one wheel, the circumference would be a little lower, and the wheel would have to spin faster than the other wheels. Luckily I haven't had a flat, so I don't know if it really says which tire is low.

If the car uses this method, it can tell which wheel location is low. If it uses pressure sensors, it will have no idea where the wheel with low pressure is installed due to the fact that you might rotate your tires as Manolo1 stated.

[Gaugster]

But if it displays pressure in each tire on the dash you can easily check all 4 tires. From your seat. Which one is a lot more likely to do on a very regular basis than if one has to manually check each tire.

Lazy people under the toyota system will completely ignore their tires till they get a warning. Under the GM/Chrysler system even lazy people can check all their tires at a glance/button push.

Yes, I can see your point but all of the TPM systems are intended for lazy people that don't care about the air pressure in there tires. They won't typically check until they are forced to do so. It doesn't matter if it is convenient or not.

Reporting the exact pressure to the drive can sometime have the opposite effect. In a situation where the tire is just below the warning pressure threshold for instance, the air pressure will increase as the wheel warms up from use. Drivers could use this to ignore the warning. The sensors have the ability to compensate for temperature before triggering a warning but it depends on how each system is implemented.

There are so many ways for drivers to use or misuse the TPM information. Sometimes less is more but each to there own.

[Gaugster]

"The car knows which sensor code has low pressure, but I don't think it knows which wheel the particular sensor is installed in."

I just rotated my tires switching rims, there is no way any sensor can know which tire is low after you do that.

How can the "Z" tell you which tire is low?

fn: of course I also rotated the tires within the rims and switched rims to the opposite side

There is another way some cars detect low tire pressure. My Sienna minivan has 'indirect' TPMS. It doesn't use any pressure sensors in the wheels. It watches the rotational speed of each wheel. If pressure is low in one wheel, the circumference would be a little lower, and the wheel would have to spin faster than the other wheels. Luckily I haven't had a flat, so I don't know if it really says which tire is low.

If the car uses this method, it can tell which wheel location is low. If it uses pressure sensors, it will have no idea where the wheel with low pressure is installed due to the fact that you might rotate your tires as Manolo1 stated.

The indirect method has one problem. The wheel speed sensors from the ABS system are used as inputs to the TPM system. However a relative measurement is used to determine if one tire has a lower pressure than the others. So if all of the wheels slowly lose air over time, the system has a hard time detecting this condition.

However, this system is almost free to implement on a newer car with ABS. A lot of cars have this system because the NHTSA gave the OEM’s a short timeline to make TPMS a standard safety feature. But I think the eventually extended the deadline. A similar thing is going on for stability control.

Some systems can learn which active sensor is located at a specific wheel position. Basically a trigger antenna is mounted in each wheel well. The wheel sensor is then triggered to send pressure data when it is requested to do so. This is the highest cost system that gets around the problem you mentioned with maintaining your tires correctly.

Regards,

[bartkat]

We expect IS drivers to be car enthusiasts who will check their tires every month manually and who will be savvy enough to check tire pressures whenever there is a change of seasons which makes a change in ambient temperature. Listen to Mario on the Firestone commercials and check your tires. :D