I have been reading and searching on here about this system and as I understand it there is no actual sensors inside of the wheels and that the ABS system and ECU work together to constantly calculate the diameter of the tire and send a warning signal if any of the tires diameters change. Is this correct? The dealer I go to says that there are definetly sensors inside of the wheels and even quoted me $106 each if they should ever go bad. What is the truth?

 

There may be some "sensors" in the wheel that assist. But the method for calculation you described is pretty much correct. The sensors that may or may not be inside the wheel are not used to calculate ACTUAL pressure.

I've heard though that the 07s may include actual tire pressure. Not sure though.

 

Thanks for the reply. Do you or anyone else have visual confirmation of whether or not these little sensors actually exist inside of the wheels? Mine is an 06. When did they add this system?

 

There are no actual sensors in the tires for this system. The '07 will have an actual sensor in the valve stem however which will monitor actual tire pressure...

 

The 05 and 06 use the existing ABS system to mneasure the wheel speeds at all four corners. When one tire changes its roatation in relation to the other wheels for an extended period of time it will trigger the TPS light. Its not the best system in the world since it wont sense a tire blowout, but its good to warn you about a slow leak.

No comment on what the newer models will have

 

yep, there are no sensors inside the wheels. there is a speed sensor at each wheel.

quoting from the manual CHASSIS- tire pressure warning system, pages CH-52 to CH-57:" when the tire pressure warning system detects a drop in the tire inflation pressure while the vehicle is in motion, a tire pressure monitor ECU turns on the low tire pressure warning light. the tire pressure monitor ECU, which is enclosed in the skid control ECU, controls this system. the skid control ECU is integrated with the brake actuator. the tire pressure monitor ECU calculates the tire inflation pressure based upon signals from each speed sensor.

how it works basically, is by using a "relative wheel speed difference(rolling radius difference method)"....when the tire inflation pressure drops, the actual radius of the tire decreases. as a result, the wheel speed increases. the tire pressure monitor ECU compares the speed of each of the four wheels, and detects a drop in the inflation pressure from their difference.

most of the components of this system belong to the brake control system. therefore, this system does not have a designated diagnosis function."

it will detect a blow out.

 

Thanks everyone for the info. Im kinda glad the system is the way it is because it will save alot of time,money and effort from having to buy extra sensors for an extra set of wheels or switching sensors back and forth all the time between wheels. I actually called the guy back at the dealership and asked about the sensors again and he seemed pretty confident that there are sensors inside the wheels. Perhaps other models use a "true" system and maybe he assumes the tC is the same? I also wonder where he got the $106 for each sensor from, since it doesnt even use them.

 

it uses sensors, they're just not in the wheels.

 

I'm pretty sure I dont need a warning light to tell me I have a blowout So I am not too worried about that part...

 

Other models like the avalon and the new camry do use the sensors inside each tire valve that measure the pressure...

...maybe thats what the guy was thinking.

 

Tell me about it. I just remember that someone posted a while back saying the TPS system didnt work because they got a blowout and the light didnt come on....And if someone had a blowout and didnt realize it....well thats a completely different issue.

 

...My car looks good enough that I usually walk around it admiring its beauty before I get in. That being said...I usually can see for my own eyes that my tires are low on air.

 

Oh yeah?

http://www.tirerack.com/tires/tirete...e.jsp?techid=1

 

Thats why they tell you to check your tires. It takes a few minutes to do and can be done by anyone. It will increase your tire life and gas mileage saving you money.

 

all newer cars by 2008 will have tire pressure sensors because it will be required by law to have them. companies are just slow to get them out because it is not needed until then...

 

I just swapped rims on my '07 and ta-da my tire pressure warning light is on. Looking at my old rims - I see why- the sensor is pretty clearly right there on the valve stem. What I want to know - is how can i disable the warning light? I really dont care about having this fancy (lol) warning system built into my car. If I ever replace the rubber, I'll have them throw these back into the car - but until then they'll be in the trunk. I just want the warning light to go out. Anyone?

 

"bump" "bump"

 

lol, what you mean "bump bump" - not sure what you're joke is.

 

he was bumping to put this post at the top of the list so it will get answered. Not sure why cause it already really has been if all the posts are read.

To disable it, you can remove the LED from the cluster.. would take about 30 minutes total if you do it right. Or, you could just take it to a tire shop and get the sensors installed as long as they fit the new wheels.

And to the comment before about being able to "see" if your tires are inflated correctly, that is completely untrue, especially on a low profile tire. I have seen them look ok and be 10 pounds below spec, or over spec.

 

yeah taking out the LED would be a bea-atch. I dont want to take apart that part of the dash. The center console/climate/radio is one thing - but I'm not touching the dash cluster. I'm just surprised theres not a way to do it - theres enough other 'easter eggs' with this car. I think I'll 'let it be' for now until it really bothers me - and evaluate swapping the stems for a few bucks whenever it becomes annoying to pay for that - i need to relax and enjoy my new wheels, ha.

And I have another question that i'm sure everyone can comment on. This is my first time getting aftermarket wheels. And I might be nuts - but the drive feels different. i see the weights and I know the place balanced the tires - there is no 'vibration' (or audible vibration at least). It just feels stiffer maybe. (Hard to describe).

And yes the wheels are the same size and are on the stock rubber. Maybe air pressure? What is the Scion tc recommended air pressure - I'm sure these guys werent so thorough with that aspect. Besides air could it be anything else?