''Check Engine Soon'' light Stays On.

First, check the tire pressure of the spare. If all tires are properly inflated, then one of the sensors are bad and must be replaced.

Reset by disconnecting battery and wait 3 to 5 minutes reconnect!

TPMS - TIRE PRESSURE MONITOR WARNING LIGHT
NOTE: Tire pressure rises and falls depending on heat caused by vehicle's operation and the outside temperature. If outside temperature is low, the air inside the tire may cool, causing a lower tire inflation pressure. This may cause the low tire pressure warning light to illuminate.

When the tire pressure warning light comes on, immediately check the air pressure of all tires and adjust to the specified pressure. Make sure the warning light goes off. If the warning light stays on or flashes, there is a malfunction in the TPM system. See appropriate manufacturer service information.

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most likely culprit is the tps itself they go bad if air is good all around then usually the sensor goes most go when fix a flat is used it shorts them out when you go to change tire replace the bad one cost anywhere from $ 5 to $ 25 online

The Anti Lock Brake System on a Mercury should store a trouble code that can be read with special equipment to let you know what the system is seeing wrong that caused the light to stay on. This code is usually stored for up to a week even when the light is not on.
It is possible that a low tire is causing the ABS system to think one of the tires is spinning too fast while braking and set the light. A low tire has to spin a little faster to keep up with the rest, which can appear to the computer as an anti lock brake situation or even an error. The correct tire pressure is listed on a sticker in the drivers door jamb.

The yellow exclamation mark appears when your TPMS, AKA tire pressure monitoring system picks up on a low-pressure tire. It means that your tires aren't inflated to the recommended pressure. A simple fix is to inflate to the required PSI, and if the problem does not go away, drive down to the nearest garage, as you may have punctured tire at your hands.

32 psi is the usual recommended pressure but you may have to fill the tires to 35 psi to make the TPM system reset. That's how most systems recognize that you have serviced the tires. Most TPM systems will indicate low tire pressure around 26-28 psi.

That is low tire pressure sensor. Check your tires and make sure that they are inflated correctly. If they are and the light still stays on then you possibly have a bad sensor that will need to be diagnosed, but check air pressure and add the correct amount, 36 psi

Hi, this is indicating a low tire pressure issue. The first thing to do, is check all of the pressures, according to the list on the label of the driver door. I say check all, because, if you have had the wheels off, new tires, brakes, or rotations, the relearn may not have been done, and the tire positions, may not be as described. So check all pressures, and if 1 is low, this is the issue. If they are all good, and the light persists, you need to visit the dealer, as you may have a problem with a sensor. Good luck...Coop

New computer (PCM)