Hazard Warning Switch - Operation

OPERATION

The hazard switch features a push-push type latching push button. The hazard switch receives a clean ground on one terminal from the Electro Mechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) Whenever the hazard switch is in its latched and lowered position, the hazard warning system is selected and the upper instrument panel switch pod circuitry sends a hard wired output to the Front Control Module (FCM).

When the FCM receives a hazard switch input it then controls hazard warning system operation and flash rate by controlling battery voltage outputs through high side drivers on the right and left turn signal feed circuits. The FCM also sends the appropriate electronic messages back to the EMIC to control the illumination and flash rate of the right and left turn signal indicators, as well as to control the click rate of an electromechanical relay soldered onto the EMIC electronic circuit board that emulates the sound emitted by a conventional hazard warning flasher. The EMIC then sends messages back to the switch pod over the Local Interface Network (LIN) data bus to control the illumination of the hazard switch push button.

The hazard switch as well as the hard wired inputs and outputs of the switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the electronic controls and communication between other modules and devices that provide some features of the hazard switch or the hazard warning system. The most reliable, efficient, and accurate means to diagnose the hazard switch or the electronic controls and communication related to hazard warning system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.