Tires and Wheels problem
2008 Mercury Marquis V8 Front Wheel Drive Automatic 50000 miles
this light keeps going on and I have had it checked by the dealers. They could only check it when the light comes on. It comes on when I am on the highway sometimes and other times it does not. Unfortunately it doesn't come on when I am near the dealership. They kept it for a few days and could not find out what was wrong.
The Tire Pressure Monitor (TPM) system monitors the air pressure in the 4 road tires with wheel-mounted tire pressure sensors. The sensors transmit radio frequency signals to the Driver Door Module (DDM) approximately every 60 seconds when the vehicle speed exceeds 20 MPH (32 KM/H). If vehicle is stationary for more than 30 minutes, the sensor will enter into a " sleep mode" and stop transmitting.
Each tire pressure sensor transmission is compared against a low-pressure limit (pressure listed on vehicle certification label minus 25 percent, which will be about 6-9 psi).
If it is determined that the tire pressure has fallen below this limit, the DDM sends a message to the instrument cluster, which then illuminates the low pressure warning indicator and displays the appropriate message(s) in the message center (if equipped).
The battery-operated tire pressure sensors are mounted to metal brackets (called cradles) on the wheels inside the tires.
The sensors are mounted 180 degrees from valve stem.
The tire pressure sensor may be serviced separately, but the cradle and strap must be replaced together
When the tire pressure warning light comes on solid and message center displays " LOW TIRE PRESSURE", check the air pressure of all tires and adjust to the specified cold pressure listed on vehicle certification label (found on driver's door or door pillar).
Drive the vehicle at 20 MPH (32 KM/H) for at least 2 minutes.
If the vehicle has been stationary for more than 30 minutes, a TPM sensor Activation procedure may be needed.
Make sure the warning light goes off. If the warning light stays on, there is a malfunction in the TPM system.
When the tire pressure warning light flashes for 70 seconds and then remains illuminated, after bulb-check has been performed and message center displays warning messages, there is a malfunction in the TPM system.
Under the following conditions, the TPM system may not function properly: Low tire pressure.
Tire pressure sensor is missing or damaged.
Spare tire is installed as a road wheel.
Incorrect tire pressure sensor is installed.
Tire pressure sensor installed incorrectly.
Non-OEM wheels installed (aftermarket rims).
Non-OEM equipped run-flat tires installed.
Other non-OEM modifications (roll cages, service barriers, part racks, ladder racks, etc.)