Switch, Hazard Warning: Operation

The hazard switch has a path to ground at all times through the instrument panel wire harness. Whenever the hazard switch is in its latched and lowered position, the switch bank circuitry provides a hardwired ground signal output to the Body Control Module (BCM) and the hazard warning system is selected. When the BCM 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, front and rear turn signal feed circuits.

The BCM also sends the appropriate electronic messages to the Instrument Panel Cluster (IPC) over the Controller Area Network (CAN) data bus 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 IPC electronic circuit board that emulates the sound emitted by a conventional hazard warning flasher.

The hardwired circuits for the hazard 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 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.