Principles Of Operation
Tire Pressure Monitoring System
Principles of Operation
The Tire Pressure Monitoring System (TPMS) monitors the air pressure of all 4 road tires. The wheel-mounted tire pressure sensors transmit via radio frequency signals, to the Driver Door Module (DDM). TPMS functionality is integral to the DDM. These transmissions are sent approximately every 60 seconds when the vehicle speed exceeds 32 km/h (20 mph). The TPMS function compares each tire pressure sensor transmission against a low-pressure limit. If it has been determined that the tire pressure has fallen below this limit, the DDM communicates this on the vehicle communication bus to the Instrument Cluster (IC). The IC then illuminates the TPMS indicator and displays the appropriate message(s) in the message center (if equipped).
For vehicles with different front and rear tire pressures (such as the E-Series and certain F-Series), the tire pressure sensors must be trained following a tire rotation. Failure to train the sensors will result in a false low tire pressure event, which will cause the TPMS indicator to illuminate.
For vehicles with the same tire pressures for front and rear tires, tire rotation will not affect the system.
Ambient Temperature Change and Tire Pressure
WARNING: The tire pressure monitoring system (TPMS) sensor battery may release hazardous chemicals if exposed to extreme mechanical damage. If these chemicals contact the skin or eyes, flush immediately with water for a minimum of 15 minutes and get prompt medical attention. If any part of the battery is swallowed, contact a physician immediately. When disposing of TPMS sensors, follow the correct procedures for hazardous material disposal. Failure to follow these instructions may result in serious personal injury.
NOTICE: Do not inflate tire higher than maximum pressure stamped on tire sidewall. Premature tire wear or damage to the tire may result.
Tire pressures fluctuate with temperature changes. For this reason, tire pressure must be set to specification when tires are at outdoor ambient temperatures. If the vehicle is allowed to warm up to shop temperatures, and the outside temperature is less than shop temperature, the tire inflation pressure must be adjusted accordingly.
If the tires are inflated to specification at shop temperatures and the vehicle is moved outdoors when the outdoor ambient temperature is significantly lower, the tire pressure may drop enough to be detected by the TPMS and activate the TPMS warning lamp indicating a low tire condition.
As the ambient temperature decreases by 6°C (10°F), tire pressure decreases 7 kPa (1 psi). Adjust the tire pressure by 7 kPa (1 psi) for each 6°C (10°F) ambient temperature drop as necessary to keep the tire at the specified Vehicle Certification (VC) label pressure. Refer to the following tables to adjust the tire pressure indoors for colder outside temperatures.
Tire Pressure Monitoring System (TPMS) Indicator and Message Center Messages
The TPMS indicator and vehicle message center (if equipped) sometimes displays faults that cannot be resolved by the customer. Treat these messages as TPMS faults that must be serviced.
Tire Pressure Monitoring System (TPMS) Indicator Illuminates Continuously
NOTE: A full-sized, matching spare wheel and tire, that is identical to the road wheel and tire, is available as an optional accessory. This spare wheel and tire is equipped with a tire pressure sensor but the sensor is not initially programmed to the Driver Door Module (DDM).
If this spare wheel and tire is in use on the vehicle, the sensor must be trained to the DDM and the remaining 3 sensors must be retrained to the DDM as well. If all 4 sensors are not trained to the DDM, the TPMS warning indicator will illuminate.
Make sure that all the wheels and tires installed on the vehicle are inflated to the correct pressure and trained to the DDM before attempting to diagnose a TPMS concern. Refer to Tire Pressure Monitoring System (TPMS) Sensor Training Tire Pressure Monitoring System (TPMS) Sensor Training.
NOTE: If the spare tire is in use (including the optional full-sized, matching spare wheel and tire), the damaged road tire must be repaired and installed on the vehicle to restore complete TPMS functionality before carrying out any diagnosis.
NOTE: For vehicles with different front and rear tire pressures (such as F-Series and E-Series), the tire pressure sensors must be trained following a tire rotation. Failure to train the sensors will result in a false low tire pressure event, which will cause the TPMS indicator to illuminate.
For vehicles with the same tire pressures for front and rear tires, tire rotation will not affect the system.
1. The TPMS indicator remains on continuously for the following condition:
- Low Tire Pressure - The TPMS indicator is illuminated solid and the message center displays LOW TIRE PRESSURE (if equipped). This is displayed when any of the tire pressures are low. When this condition exists, the tire pressure must be adjusted to the recommended cold pressure as indicated on the VC label.
2. NOTE: The TPMS sensors do not transmit when the vehicle is stationary. If the vehicle has been stationary for more than 30 minutes, it will be necessary to wake up the sensors so they will transmit the latest tire pressure information to the DDM.
If the vehicle has been stationary for more than 30 minutes, activate the TPMS sensors. Refer to Tire Pressure Monitoring System (TPMS) Sensor Activation Tire Pressure Monitoring System (TPMS) Sensor Activation.
Tire Pressure Monitoring System (TPMS) Indicator Flashes
The TPMS indicator flashes for 70 seconds and then remains ON solid when the ignition key is turned to the ON position for the following conditions:
1. Tire Pressure Sensor Fault - If equipped, the message center will display TIRE SENSOR FAULT when a tire pressure sensor is malfunctioning. GO to Symptom Chart. Symptom Related Diagnostic Procedures
2. No Communication With the DDM (TPMS is integral to the DDM) - The TPMS indicator is illuminated when the Instrument Cluster (IC) has received no signals from the DDM for more than 5 seconds. If equipped, the message center displays TIRE MONITOR FAULT. GO to Symptom Chart. Symptom Related Diagnostic Procedures
3. Tire Pressure Monitor Fault - If equipped, the message center will display TIRE MONITOR FAULT when the tire pressure monitoring system is malfunctioning or communication with the IC has been lost. GO to Symptom Chart. Symptom Related Diagnostic Procedures