Tire Monitoring System: Description and Operation
TIRE PRESSURE MONITORING SYSTEMDESCRIPTION
BASE TIRE PRESSURE MONITORING
This system will consist of tire pressure monitoring sensors attached to each wheel through the valve stem mounting hole, a central receiver module (WCM) and a yellow telltale. A sensor shall be installed in the spare wheel if the vehicle is equipped with a matching full size spare wheel and tire assembly.
PREMIUM TIRE PRESSURE MONITORING
The system will consist of tire pressure monitoring sensors attached to each wheel through the valve stem mounting hole, a wireless control module (WCM), Three Wheel Sensor transponders are mounted in the wheel wells (2 in the front and 1 in the rear wheel wells). a re-configurable dot matrix display module and an amber colored ISO standard Indicator Lamp. A sensor shall be installed in the spare wheel if the vehicle is equipped with a matching full size spare wheel and tire assembly.
WIRELESS CONTROL MODULE (WCM)
The receiver circuit for the TPM system is integrated into the WCM. The WCM also includes the Remote Keyless Entry (RKE) receiver and the Sentry Key Immobilizer (SKIM) receiver. All three receivers share a number or common components. The WCM decodes the RF signals transmitted by each of the vehicle's tire pressure sensors. The decoded information is used to determine if "warning" or "fault" conditions exist within the TPM system.
The WCM communicates with the module that controls the "ISO Indicator Lamp" and the text display (Premium system), via the vehicle bus system (CAN B).
Upon detection of a warning or fault condition, the WCM will send a request to illuminate the yellow telltale. Also, upon detection of a warning or fault condition, the display module will send a request to sound the "chime". A chime will only be requested once per ignition cycle per warning or fault condition detected.
The WCM will store all warning and fault conditions, placard pressure values, low-pressure threshold values and low pressure threshold hysteresis values in memory that can be accessed through diagnostic communication. If new sensors are introduced to the vehicle, the data stored for the sensor being replaced will be deleted.
The WCM will store all wheel sensor ID's and locations and faults in memory that can be accessed through diagnostic communication. All other data values transmitted from each active wheel sensor (not the spare tire) shall be stored in the WCM memory
OPERATION
BASE TIRE PRESSURE MONITORING
The tire pressure monitoring system is designed to operate without loss of function for all types of standard tire constructions. (Function with different types of run flat tire constructions needs to be evaluated for each design). The wheel sensor shall monitor tire pressure, air temperature inside the tire, wheel acceleration and the sensor internal battery status for all four active road tires. The sensor will broadcast this information, along with a unique 32 bit ID, to a central receiver circuit located inside the WCM. The information received by the WCM will be decoded and stored in memory (RAM) in the WCM. If a "warning or "fault" condition exists, the WCM will send a bus message request to illuminate the yellow telltale and to sound the chime.
If the WCM detects a warning or fault condition at ignition key "on" it will wait ten seconds +/- 10 % before sending the first request to illuminate the yellow telltale. This will assure that the display module has concluded its bulb check period. The display module will request a chime once per ignition cycle for each "warning" or "fault" condition detected. A "warning" or "fault" condition will remain enabled until the problem causing the condition is corrected and removed/reset.
The WCM shall continuously monitor for the receipt of tire pressure RF message transmissions from the wheel sensors during both the ignition key "on" and key "off" cycles. The wheel sensor ID's and the location of each sensor (e.g. Tire 1, Tire 2 etc.) are stored in the WCM non-volatile memory during the initial Manufacturing Plant Process, or during a service procedure, as required. The recommended "placard pressure", "low-pressure threshold" and "Hysteresis Pressure Values" for the tires installed on the vehicle, are stored in the WCM non-volatile memory during the initial Manufacturing Plant Process, or during a service procedure, as required. (Note: For vehicles with optional wheel/tire sizes and significantly different tire placard pressures, the placard pressure value and the low pressure threshold value shall be re-programmable by the dealer to accommodate the customer selected wheel/tire combinations recommended by Daimler Chrysler).
PREMIUM TIRE PRESSURE MONITORING
The tire pressure monitoring system is designed to operate without loss of function for all types of standard tire constructions. (Function with different types of run flat tire constructions needs to be evaluated for each design). The wheel sensor shall monitor tire pressure, air temperature inside the tire, wheel acceleration and the sensor internal battery status for all four active road tires and the spare tire, if so equipped. The sensor will broadcast this information, along with a unique 32 bit ID, to a central receiver circuit located inside the WCM. The information received by the WCM will be decoded and stored in (RAM) memory in the WCM. The WCM will send bus messages to the re-configurable display module to display the pressures of the four active road tires in vehicle position. The spare tire pressure is monitored but it is not displayed.
If a "warning" or "fault" condition exists, the WCM will send a bus message request to display the text messages and, when required, illuminate the yellow telltale. "Warnings" and "faults" are described in more detail below. If the WCM detects a warning or fault condition at ignition key "on" it will wait ten seconds +/- 10% before sending the first request to illuminate the yellow telltale and to display the text messages. This will assure that the display module has concluded its bulb check period. The display module will request a chime once per ignition cycle for each "warning" or "fault" condition detected. A "warning" or "fault" condition will remain enabled until the problem causing the condition is corrected and removed/reset
The WCM shall continuously monitor for the receipt of tire pressure RF message transmissions from the wheel sensors during both the ignition key "on" and key "off" cycles. The wheel sensor ID's and the location of each sensor (e.g. Left Front, Right Front etc.) are stored in the WCM non-volatile memory during the initial Manufacturing Plant Process, or during a service procedure, as required. The recommended "placard pressure", "low-pressure threshold" and Hysteresis Pressure Values for the tires installed on the vehicle, are stored in the WCM non-volatile memory during the initial Manufacturing Plant Process, as described later in this document or during a service procedure as required. (Note: For vehicles with optional wheel/tire sizes and significantly different tire placard pressures, the placard pressure value and the low-pressure threshold value shall be re-programmable by the dealer to accommodate the customer selected wheel/tire combinations recommended by Daimler Chrysler).