Filter
Top Products
General Information 1-11
Section 1: General Information
Tire Pressure Monitoring System (TPMS) Principles of Operation
The tire pressure monitoring system (TPMS) monitors the air pressure of all 4 regular road tires.
The tire pressure sensors, attached to each rim by a metal band located in the drop well, transmit
via a 315 Mhz radio frequency signal to the internal antenna of the smart junction box (SJB).
These transmissions are sent approximately every 60 seconds when the vehicle speed exceeds
32 km/h (20 mph). The SJB compares the tire pressure data against a low-pressure limit. If the
module determines that the tire pressure has fallen below this limit, the module communicates this
on the vehicle network to the instrument cluster (IC) and illuminates the TPMS indicator solid. If
there is a system malfunction, the TPMS indicator flashes for 70 seconds and then goes solid.
This vehicle, as delivered by Ford Motor Company, conforms to Standard FMVSS138, Tire
Pressure Monitoring Systems.
This system may not function if any of the following components are removed, relocated or
modified in any way:
• OEM wheels and tires
• Tire pressure sensors, cradles and bands
• SJB
• SJB software and calibrations
• IC
• IC software and calibrations
• Instrument panel wiring
• Wheel bases greater than originally released
Certain modifications could cause reduced system performance, including the complete loss of
TPMS functionality. This may include:
• Non-OEM wheels or tires
• The addition of steel carcass or run-flat tires
• Removal of tire pressure sensors, cradles or bands
• Modification of the recommended tire pressure
• Modifications to the mounting location of the SJB
• Modifications or re-location of the harness supplying the SJB and IC modules
• Addition of metallic structures, such as prisoner partitions, may affect the signal strength of the
sensors and could interfere or prevent the SJB from hearing the sensors
• Addition of intended or unintended transmitters to the vehicle may affect the signal strength of
the sensors or interfere SJB internal antenna
2010 Expedition SSV Modifiers Guide, 07/2009