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TPMS is beeping at me with 34/35 psi


onecrazyfoo4u

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I don't understand what's going on. I've manually checked the tire pressure and they are all at 35psi (same as the day I bought it 4 months ago). Now when I start the car everytime, it beeps at me and displays the message with all 4 tires showing 31psi. Then I start to move and they go up to 34-35psi and stay up there for the rest of the drive. But the warning message is still latched the whole time.

Does the warning realy go off with 1 psi low tire pressure? You would think it wouldn't go off until 5-10 psi low (like my old Malibu). Why does it go off with 34-35 psi in the tires? Super wierd...

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I've had one low tire before that had a slow leak. The TPMS warning would not go off until I got that tire up to 36 psi. My suggestion - inflate all tires to 36 psi, which is what they are supposed to be at anyway. That SHOULD clear the TPMS warning.

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You would think it wouldn't go off until 5-10 psi low (like my old Malibu). Why does it go off with 34-35 psi in the tires? Super wierd...

...maybe because properly inflated tires are the best way to maintain your tires and provide better fuel economy. I would find it more weird if the vehicle was warning me at 5-10 psi lower....at that much lower you wouldn't need the TPMS sensor as you would be able to visually see they are low.

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  • 2 months later...
  • 3 months later...

Most tire monitoring systems respond to "underpressure" at around 10% of nominal (target) pressure. For a car that is supposed to be aired to 36 psi, then the TPMS, should, start warning you when the monitor is seeing < or = to 32 psi at the tire. Bear in mind that not all tire gauges are accurate to more than + or - 10% for the low cost variety (sliding vane style) and the digitals, depending on what you spent on it may only be accurate to + or - 3% of the reading.

FWIW, whenever I get a new car, I start "shopping" for tire gauges that match the TPMS reading... Over the years I've accumulated a lot of tire gauges and I've always got one that matches now, but, before my collection, I'd just start buying "mid price range" digital gauges until I found one that matched what the TPMS was reporting and that's the one that stays in the car for "on the road" fills. In my shop, I've got a professional digital tire gauge/filler unit that is accurate to .1% and that is the one I use to do major service to the tires on all of my vehicles. It is too large and expensive though to carry one in each vehicle I own.

The recommended 36 psi cold inflation will always go higher after you've driven for a few minutes. The inflation figure on the door frame is for "cold" inflation; after the car has sat for a minimum of 3 hours with the tires out of direct sun exposure. Whatever the pressure "warms" to after you start driving is fine; on a really hot day, they may, indeed, "inflate" to 40 psi or more and that, for the running speed and ambient temperature, is where they should be. Don't stop and let air out of the tires to get them back down to 36 psi...you'll be way too low for after the car's tires have cooled down.

As for having readings that are a mixture of metric and imperial/SAE...don't think it can be done. The convertor in the CANBus is, to my knowledge, an either / or device. You'll get all metric or you'll get all Imperial/SAE readings, no way to get a mix; you have one chip that does the conversions, all the conversions and it does it on the fly with the various inputs, which, are not metric or SAE to begin with, but, electrical pulses which are generated by optical isolators or electro-mechanical generators and pickups.

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