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Tire Pressure Sensor Advice Please


johns13

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I have a 2002 SC430 with 31k miles, on which the tire pressures are supposed to be 33/33.

A few months ago the tire pressure warning light came on and I checked all the tires - one was down to 26psi so I inflated it back to 33 and the warning light went off.

The warning light has now come on again but all the tires are at (or above) 33psi.

I called the dealer to book in the car for them to check it and the service guy tried to feed me some b/s about how the warning light might come on when the tires are cold (I measured them at 33psi when they were cold) as the sensors are "sensitive". He then told me to try inflating all the tires to 40psi.

What is the story? The warning light doesn't need a dealer to reset it, does it?

I suspect one of the sensors has hit one too many potholes and they don't want to replace it under warranty. What tire pressures do people run? Anyone else had a similar problem?

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Since it is still under warranty, I would do everything I can to get the car inspected at the dealer. Document who you spoke w/ and the particular problem. But before you do...here are some questions.

What tires are you running (the recommended stock one or a similar replacement)? Are you on the stock run flats? Are you using aftermarket wheels? What is your tire size and recommended psi (I noticed you said it should be at 33psi)?

Tire sensors should not have to be reset. That doesn't make sense. The tire system has to be easy enough for the average consumer to use, therefore the system should automatically be able to detect changes in air pressure at all times. It shouldn't have to be reset at all.

Have you had new tires installed? If so, were you told of any abnormalities/damage to the rims? Was any repair to the rims made?

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Good questions. I bought the car used from the dealer with 22k miles and 9k miles later it still has the same OE run-flat tires (Bridgestone Potenza RE040 245/40-18) and TRD wheels (factory option I think). The recommended pressure is 33/33.

No repairs have been made to the tires or rims. Last time the warning light went out when I inflated the tire back to 33psi. I suspect the bumps and thumps due to the horrible condition of San Francisco roads has broken one of the sensors - I don't know whether that is a warranty item or not.

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Since it is still under warranty, I would do everything I can to get the car inspected at the dealer.  Document who you spoke w/ and the particular problem.  But before you do...here are some questions. 

What tires are you running (the recommended stock one or a similar replacement)?  Are you on the stock run flats?  Are you using aftermarket wheels?  What is your tire size and recommended psi (I noticed you said it should be at 33psi)? 

Tire sensors should not have to be reset.  That doesn't make sense.  The tire system has to be easy enough for the average consumer to use, therefore the system should automatically be able to detect changes in air pressure at all times.  It shouldn't have to be reset at all. 

Have you had new tires installed?  If so, were you told of any abnormalities/damage to the rims?  Was any repair to the rims made?

If I remember correctly, the 33 psi is very close to the threshhold which would signal the pressure light to come on. It doens't sound like a faulty sensor but you are right at the limit for that sensor.

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You may be confusing two different causes of the warning light. The first warning light was clearly due to pressure. This one may or may not be. Since you eliminated pressure as the variable, maybe try isolating anotehr cause. Sounds like "check if the plug is plugged in" but you may check to make sure someone didn't mistakenly hit the Alternate Tire switch near the glove compartment. Hopefully, that's all there is. Otherwise, I would demand that the dealer correct the problem. ALSO, I recommend scrapping those horrendous run-flats! I did and love the car again. I swapped them for Pirelli P-Zero Nero's... quiet, stick like glue and not expensive. You won't go through rims (and pressure sensors) as easily either! :rolleyes:

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If I remember correctly, the 33 psi is very close to the threshhold which would signal the pressure light to come on.  It doens't sound like a faulty sensor but you are right at the limit for that sensor.

I inflated them all to 39 psi - light still on. *sigh* Ride doesn't seem any worse.

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...hit the Alternate Tire switch near the glove compartment.  Hopefully, that's all there is.

Hmmmm... needed a flashlight to find that little switch (not mentioned anywhere in my owner's manual!) but it was on "Main" rather than "2nd".

I am leaning more and more towards replacing the run-flats with some decent Pirellis... and upgrading my AAA membership!

Thanks for the help everyone - looks like it is something the dealer will have to see to.

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