Principles Of Operation

Fire Suppression System

Principles of Operation

The Fire Suppression System Module (FSSM) is non-repairable. The FSSM uses hardwired circuitry, internal sensors, internal back-up power supply, the Controller Area Network (CAN), and the International Organization for Standardization (ISO) 9141 communication network. The wiring harness between the FSSM and the LH and RH fire suppressors or LH and RH external actuators is contained within a rigid conduit and cannot be repaired. A new harness must be installed if damaged has occurred. The fire suppression system can be diagnosed with a scan tool through the ISO network. Communication using the CAN circuits transmits and receives data between the FSSM, PCM, and the ABS module. Refer to Module Communications Network Testing and Inspection.

It is very important to understand:

- where the input originates.
- all the information necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- whether the module which received the input controls the output of the feature, or whether it outputs a message over the CAN circuitry to another module.
- which module controls the output of the feature.

The FSSM detects high velocity rear impacts, determines vehicle motion, and deploys up to 4 suppressor squibs based on vehicle motion requirements. Deployment of the suppressor squibs activates the disbursement of a fire suppression material beneath the rear portion of the vehicle. A rear collision is sensed by 2 impact sensors located inside the FSSM. Vehicle motion after impact is determined based on deceleration and wheel speed. The Vehicle Identification Number (VIN), model year, and wheel speed information is received by the FSSM through the CAN.

If the FSSM detects a fault with any fire suppression system component, an Fire Suppression Indicator Lamp (FSIL) indicator in the Instrument Cluster (IC) is illuminated and DTCs are logged.

A manual activation switch is present as an override to the system. When the switch is pressed with the ignition switch in the ON position, voltage and ground are provided to the FSSM, and the FSSM deploys the fire suppressors or fire suppressors external actuators (if equipped).

A fire suppression system diagnostic tool is used to simulate resistance of a fire suppressor during certain diagnostic procedures.