The TPMS is a strange system. A few posts up, you will note that I installed steel rims with rubber valves for dedicated winter tires. The only tire with a sensor is the spare. For over a month, the tire pressure light did not come on, but it started to flash last weekend. I was on a highway trip. The next day, I lowered the spare to check the air pressure, it was fine, but the valve assembly was muddy from road dirt. I raised the tire, drove off, and the light has yet to come on!

Do you mean differences in tire rotation through the ABS? My light came on at around 2 weeks so the next morning I checked the pressures and the spare was up around 50 psi. Let some air out and haven't seen the light since, so leads me to believe each tire's - including the spare's - pressure is individually monitored. Guess it could be coincidence too, since the light didn't come on during those first two weeks.

I have read that there are two types of Tire Pressure Monitoring systems. One type is based on ABS, and I recall that the RAV4 had that style. I recall that the 4Runner was believed to have the 'direct' system, and I believe that each wheel emits a radio frequency signal to the computer. In the case of my spare tire (which has the sensor), I believe a build up of dirt affected the radio signal. By checking the air pressure, I dislodged dirt and the light has not came on since.

Baffling is that the dealer indicated that the light would either flash or stay on constant with rubber valves. That does not appear to be the case. I surmise that the system will only display a tire pressure fault when the wheels are equipped with the sensors - no sensor, no radio signal.

Any other theories welcome.

Today, I went up to the mountains to enjoy some snow. The blinker went back on and won't turn off again!

I am not going back to the dealership and wait another 6 hours to get this thing turned off!!! Argh!!! I'm going to open up the dang thing and take out the tiny light bulb that makes it blink.

here is another thread on the TMS.
http://www.toyota-4runner.org/showth...&threadid=2795


if you have packed snow in the wheel wells or around the spare you may get erractic sensor readings.

I sympathize with you, really ... I feel pretty irked too, I'm ready to take it to the dealer one more time and if it happens again, just turn the damn thing off because I think I can SEE when my tires are going low ...

My tires barely grazed the snow. Most of it was melted, so I think I can rule that part out. I'm thinking that the air pressure made the tires lose some air? I had some water bottles in the car and the bottles are still compressed due to the altitude pressure.

I'm getting a set of 4 OEM Sport 17s for the winter but they don't have the tire pressure sensor in them. I was quoted $160CAD per sensor for new ones! Anybody know where to buy these online?

leftyrb your scenario gives me hope that I may not need them considering the $700 price tag.

jjjheimer

If you have bought the sport model, the usual 'take-off' rims won't fit the Sprt, due to the larger calipers.

You can buy new sensors from the dealer or a grommet kit that I think would include the rubber parts that can be used when mounting the sensors in another set of rims.

The second set of wheels are 17 inch sport wheels. I spoke with my dealer today regarding sensors - they're quoting $140 per wheel. Which sucks ass. I was really hoping to avoid them entirely and the dealer is taking the easy way out - saying they don't know what will happen, and pulling the fuse may trigger a CEL and why don't you just buy new sensors to be on the safe side. I am I reading your post right - that you've got a set of winters without sensors that don't set off the TPMS dash indicator?

I am I reading your post right - that you've got a set of winters without sensors that don't set off the TPMS dash indicator?

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Yes, I do have a set of winter wheels without sensors. Sometimes the dash indicator illuminates and as other times, it does not. Don't have an explanation

I don't know yet - they are not on the truck. I'm trying to ascertain in advance what is going to happen if I install them without the sensors, and if this is even an option.

just thought i'd add my experience.... 3 weeks ago i went up to the mountains to do some snowboarding. i've never before had my TPMS light come on. woke up in the morning and on my way to the slopes it lit up (constant on). i stopped the car, checked the pressures, all around 34, and continued on my way. when i was done riding for the day and driving back to the condo, the light went out. i've had this happen to me now 3 times. its on after a cold night, and off in the afternoon. i went up to the mountains a lot last year, and it never lit up then.... and it only does it intermittently to me now. the car has never been covered in snow, just in cold weather.

so, i dont know whats going on, but as long as the symptoms are always the same, i'm ok with it it... i guess

I bet your spare is low. Check it.

The air pressure sensors are little wireless transmitters mounted behind the valve in each wheel, even the spare. The receiver is between the headliner and the roof, toward the rear of the vehicle. The sensors are powered by a lithium battery mounted to each sensor. To get the maximum life from the lithium battery (who wants to dismount a tire just to change a battery?) the sensors don't transmit until the pressure gets too low. Then the tire with the low pressure (remember the Ford Explorer/Firestone tire debacle?) transmits the problem to the receiver and voila the Low Tire Pressure dash light comes on.

So, if you are using aftermarket wheels, with no sensors, this is not a problem because there is no sensor available to transmit the low pressure warning.

Keep in mind when having any tire/wheel service performed that you should mention to the technician that the sensors are there. Else they might damage them. Some tire companies don't even want to mess with these factory wheels at all, for fear that the customer will blame them if the low pressure warning system someday stops working.