Tire Monitoring System: Description and Operation

DESCRIPTION

WARNING LAMPS





TREAD Lamp
- Tire Under Inflation / Leak Warning.




1. Turn on condition
A. When tire pressure is below allowed threshold
B. When rapid leak is detected by the sensor.
C. Indicates that tire needs to be re-inflated to placard pressure / repaired.
2. Turn off condition
A. Under-inflation ; When tire pressure is above (warning threshold + hysteresis).
B. Rapid Leak ; When tire pressure is above (leak warning threshold).

DTC Warning




1. Turn on condition
A. When the system detects a fault that is external to the receiver / initiator / sensor.
B. When the system detects a receiver fault.
C. When the system detects an initiator fault.
D. When the system detects a sensor fault.
2. Turn off condition
A. If the fault is considered as 'critical', then the lamp is held on throughout the current Ignition cycle (even if the DTC has been demoted). This is because it is important to bring the problem to the drivers attention. On the following Ignition cycle, the demotion conditions will be re-checked. If the demotion conditions occur, the lamp will be turned off. It will be held on until DTC demotion checking is completed.
B. 'Non critical' faults are those that can occur temporarily e.g. vehicle battery under voltage. The lamp is therefore turned off when the DTC demotion condition occurs.

SYSTEM FAULT
1. General Function
A. The system monitors a number of inputs across time in order to determine that a fault exists.
B. Faults are prioritized according to which has the most likely cause.
C. Maximum fault store is equal to 15.
D. Certain faults are not covered through DTC. The main ones are:
1) Speed input. This is important since it is required for Auto-Learn & DTC. Requires diagnostic check of speed while driving vehicle to diagnose.
2) Sensor thermal shutdown (over 257°F/125°C).
3) Receiver Micro-controller lock up ; requires observation of lamps at Ignition ON to diagnose.
4) Ignition Line stuck ; requires observation of lamps at Ignition ON to diagnose.