Grand Cherokee 2WD V6-3.7L (2008)
Tire Pressure Sensor: Description and Operation
Operation
OPERATION
NOTE: On vehicles equipped with a Tire Pressure Monitoring System (TPMS), when the spare tire pressure sensor is replaced with a new
pressure sensor, a diagnostic scan tool MUST be used to run a routine that will program the new pressure sensor ID into the Wireless Ignition
Node (WIN). Please copy the ID number off of the new pressure sensor before installing it into the spare tire. Then follow the programming
steps outlined in the diagnostic scan tool for: "Program Spare Tire Sensor ID" under Miscellaneous Functions for the WIN (Wireless Ignition
Node) menu item as appropriate.Then install the spare tire with one of the active road tires.
NOTE: If replacing the WIN, the spare tire must be dismounted from its wheel to access and note the spare tire pressure sensor ID. Then follow
the programming steps outlined in the diagnostic scan tool for "Program Spare Tire Sensor ID" under Miscellaneous Functions for the WIN
(Wireless Ignition Node) menu item as appropriate. The WIN learns the Placard Pressures from the Front Control Module (FCM)
configuration on the bus. Go to "Read Placard Pressure" under "Data Display" for the "WIN/Wireless Ignition Node" and confirm the
placard pressure reported matches Tire Inflation Pressure (Placard) Label.
The battery operated tire pressure sensor is both a transmitter and a receiver. The TPM sensor can be forced to transmit if using a special tool such as a
TPM-RKE Analyzer, or from a transponder. The TPM-RKE Analyzer has the ability to change the sensor's operating mode and to diagnose a faulty
TPM sensor. Using a TPM-RKE Analyzer can take up to a minute to force a transmission from a sensor. The TPM sensor can be in one of the following
modes:
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Sleep Mode - This is the operating mode of a new TPM sensor. If placed on the vehicle as a road tire, the sensor will transmit once every 20
seconds when the vehicle is driven at speeds over 15 mph (24 km/h). If the vehicle is not moving, the sensor will only transmit on a pressure
change greater then 1 PSI. Driving the vehicle continuously at this speed for more then 4 minutes, and then stopping the vehicle will change the
sensor state into Park Mode. If the vehicle is equipped with a full size matching spare tire and the spare tire sensor has been replaced, The sensor
must be changed to Park Mode to conserve battery life. Either use a TPM-RKE Analyzer, or swap the spare tire with a road tire.
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Park Mode - This is the correct operating mode when the vehicle is not moving. The sensor will transmit once every 13 hours to update the WIN,
or will transmit on a 1 PSI delta change. The sensors will internally take a measurement of the tire pressure every minute to determine a change in
tire pressure
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0ff / 30 Block - If the vehicle has been stopped for more then 20 minutes, or if the sensor's operating mode was forced to Park Mode using a
TPM-RKE Analyzer, the sensor's operating mode will transition from Park Mode to 30 Block Mode once the vehicle is driven over 15mph. In this
mode, the sensor will transmit once every 15 seconds when the vehicle is driven at speeds over 15 mph (24 km/h) for the first 30 transmissions.
After about 8 minutes of continuous driving above 15 mph (24 km/h), the sensor's mode will change to Drive Mode
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Drive Mode - In this mode, the sensor will transmit once every minute when the vehicle is driven at speeds over 15 mph (24 km/h). At any time
the vehicle speed drops below 15mph, the sensor will revert back to Park Mode. The sensor mode will still be in drive mode when the sensor
reaches speeds over 15 mph (24 km/h), unless the vehicle has been stationary for more then 20 minutes.
Each sensor's (transmitter) broadcast is uniquely coded so that the wireless ignition node (WIN) can monitor the state of each of the sensors on the four
rotating road wheels. The WIN can automatically learn and store the sensor's ID while driving "within 10 minutes continuously above 15 m.p.h. (24
Km/h)" after a sensor has been replaced, The vehicle must be stationary for more then 20 minutes in order to initiate the learning sequence.
