I have a 2009 ford focus and dont know how to reset the low tire pressure light

use this link.
http://enginepartsdiagram.com/2007-2016-ford-focus-tire-pressure-tpms-sensor-light-reset/

Don't forget the spare tire pressure.

Who changed the sensors , you or you had it done at a repair shop ? When the sensors are changed they need to be programmed ! There is a code stored in the TPMS module when that light is on ! Need to have module scanned for codes !

There is a procedure to do this and it should be in your owners manual. You need to buy a reset tool from Ford for about 35 dollars. The procedure goes like this.go in the car and step on and off the brake. Cycle the ignition switch on and off 3 times ending in off. Step on the brake and let off again.c Cycle the key off and on 3 times ending with the key on. Your cars horn will sound. With the key left on,use the Ford tool,holding it on the tire opposite the valve stem,press the button on the tool till the horn beeps again. This starts with the left front tire,right front tire,right rear tire and left rear tire,with having to get a beep at every tire. When you finish at the left rear tire you'll hear 2 beeps knowing you did it right. Or you can go to any tire shop,or Pep Boys and they will do it for you for a small charge.

Charge you extra for doing what should have been done? you will need the tire sensors relearned. this is always included with installation. I dont know who you are dealing with? dealer?. I dont think you can reset the sensors without a scanner.

Make sure you refill the tires with the specific amount of air and if it doesnt make the light go away you got a bad tire pressure sensor.
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The light should reset itself after driving the vehicle for 10 minutes or so out on the highway.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

What was the pressure.? the tire pressure specification should be on the drivers door jamb. It needs to be set cold. The light will go off when each tire signals that it has the proper pressure.

there is a tire pressure sensor on each tire check the air pressure on each tire and recalibrate the system each time you put air in any of the 4 tires or if any of the tire gets low air.Its like teaching the system on the present tire air pressure.One thing more the valve on each tire are special valve that have electronic part inside so make sure you dont replace them with an ordinary tire valve.Recalibrating shld be done on workshops with the proper tool

light should auto reset dont forget to check spare--and dont over inflate sets off sensor also