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autodoc_2000 , Auto Service Technician
Category: Car
Satisfied Customers: 2563
Experience:  ASE Master Tech w/ Advance Engine Performance
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2003 Ford Expedition: The tire pressure alarm..Ford dealership..spare

Customer Question

i have a 2003 Ford Expedition with tire pressure monitoring. The tire pressure alarm is going off and will not reset after tire pressure has been verified as correct. 3 different Ford dealership have given me different answers. 1 says i dont have the right pressure, 1 says the difference in my tire circumfrance
(recently installed spare has more tread than other tires on the ground) is causing the alarm to go off.
and the last says 1 of the sensors is bad and needs to be replaced.

Any help on troubleshooting???

Optional Information:
2003 Ford Expedition

Submitted: 10 years ago.
Category: Car
Expert:  autodoc_2000 replied 10 years ago.
Principles of Operation
The Tire Pressure Monitoring System (TPMS) has the ability to monitor the air pressure of all five tires. The tire-mounted pressure sensors transmit signals to the TPMS module by using the valve stem as an antenna. These transmissions are sent approximately every 60 seconds when the vehicle speed exceeds 32 km/h (20 mph) . The TPMS module compares each tire pressure sensor transmission against low and high pressure limits. If the TPMS module determines that the tire pressure has exceeded the limit, the TPMS module communicates on the SCP network to the vehicle message center, which then displays a warning message. The system is not affected by wheel and tire rotation.

Vehicle Message Center TPMS Messages
The vehicle message center sometimes displays messages that cannot be resolved by the customer. Treat these messages as TPMS system faults that must be serviced. Refer to the symptom chart for the following messages:

  • Warning-Tire Very Low

Displayed when one or more tires have very low pressure. When this warning message is displayed, a warning chime will sound reminding you to stop the vehicle as soon as safely possible and check the tires for correct pressure, leaks and damage.

Check Tire Pressure
Displayed when any of the tire pressures are high or low.

Check Spare Tire Pressure Displayed when the spare tire pressure is high or low.

Tire Pressure Sensor Fault
Displayed when a tire pressure sensor is malfunctioning.

If the customer requests that the TPMS be turned off, it can be done by configuring the message center through the Instrument Cluster (IC) , using the scan tool.

As you can see this sytem is dependant on air pressure not wheel speed. Some tire pressure systems are designed to monitor wheel speed and if it sees a difference in wheel speed it determines that that there is a low tire. This system has pressure sensors in the tires. It is a part of the valve stem. If you have the air pressure in the tire that the door sticker says you need then the problem is either a bad sensor or module.

Here is the pinpoint test for a low tire pressure warning. You will need a scan tool that can read body codes in order to properly diagnose the system.

Again the tire circumference will not turn on the message, but a bad sensor could and low air pressure will.

autodoc_2000, Auto Service Technician
Category: Car
Satisfied Customers: 2563
Experience: ASE Master Tech w/ Advance Engine Performance
autodoc_2000 and 6 other Car Specialists are ready to help you
Customer: replied 10 years ago.
Reply to autodoc_2000's Post: Your recommendation as to how i should communicate this info to the Ford repair facility??
Customer: replied 10 years ago.
Relist: I still need help.
Would you suggest printing your answer and taking it to the dealer??
Expert:  autodoc_2000 replied 10 years ago.
Yes print this out. It is from the Ford Service Manual.

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