On my 2009 Sonata I noticed tires pressure was at 45psi. It is supposed to be 32psi so I lower all four tires to 32psi and now the low pressure warning light is on. I would expect there to be some sort 'reset' function to the new pressure setting but there is nothing in the manual for this.
Does anyone know how this is done?

 

when did you check your tire pressure the first time. If you did it after a bit of a drive the tire pressure will always show high. One morning before you drive check your pressure. your probly low now, and need to add some. 45psi isnt that high if you measured it after you were driving.

 

I checked them 'cold'. This is the first time I have checked them since I got it. I thought it was riding a little rough so decided to check TP. I was surprised to find them at 45psi. Is the base setting done by the factory/service tech?

 

Sounds like a problem alright. Probably the dealer put all that pressure in the tires to make sure the TPMS light wouldn't come on.

 

The TPMS system has likely been setup in the wrong mode ("high storage" vs "normal" or "low normal" modes). Here is the link to a Hyundai technical service bulletin covering the issue:

http://www.hmaservice.com/files/331/...-SS-010PDF.pdf

The TPMS system can only be configured with a special scanner (the TPMS Exciter) by the dealer. Take the car back to the dealership along with a copy of the TSB and describe your problem. They shouln't even charge for making the needed modifications since the car was setup wrong by the dealership to begin with.

Good luck.

 

Are you sure the pressure gauge you are using is a good one? Maybe it's registering high.

For example, if it's showing 45-psi on the gauge when there is really 35-psi in the tire, and you lower the tire pressure to 32-psi on the gauge, you may really only haveabout 22-psi in the tires.

I'd double check the tires with a different gauge and see if you get the same results. If so, take it back to the dealer to reset the TPMS.