Hazard Warning Lamps: Description and Operation

TURN SIGNAL & HAZARD WARING SYSTEM
The turn signal and hazard warning system includes the following major components, which are described in further detail elsewhere in this service information:
- Combination Flasher
- Hazard Warning Switch
- Turn Signal Cancel Cam
- Turn Signal Indicators
- Turn Signal Lamps
- Turn Signal Switch

The turn signal system in this vehicle includes a turn signal warning chime feature. The EMIC monitors the turn signal indicators and sends an electronic chime request message to the Central Timer Module (CTM) over the Programmable Communications Interface (PCI) data bus network if the indicator remains illuminated with the vehicle speed above about 25 kilometers per hour (15 miles per hour) for a distance of greater than about 1.6 kilometers (1 mile). (Refer to ELECTRICAL/INSTRUMENT CLUSTER - DESCRIPTION).

The turn signal system operates on battery voltage received on a fused ignition switch output (run-acc) circuit so that the turn signals will only operate with the ignition switch in the On or Accessory positions. The hazard warning system operates on non-switched battery voltage received on a fused B(+) circuit so that the hazard warning remains operational regardless of the ignition switch position. When the turn signal system is activated, the turn signal switch and the combination flasher will cause the selected turn signal indicator, front park/turn signal lamp, and rear tail/stop/turn signal lamp to flash on and off. When the hazard warning system is activated, the hazard warning switch and the combination flasher will cause both the right side and the left side turn signal indicators, front park/turn signal lamps, and rear tail/stop/turn signal lamps to flash on and off.

In order to provide the turn signal on warning, the ElectroMechanical Instrument Cluster (EMIC) monitors vehicle speed and distance messages received from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus and the hard wired turn signal switch input to the cluster electronic circuit board. If a turn signal remains indicated for a distance of greater than about 1.6 kilometers (1 mile) and the vehicle speed remains greater than about 24 kilometers-per-hour (15 miles-per-hour), the EMIC generates a chime request message to the Central Timer Module (CTM) over the PCI data bus. The CTM then generates a chime to provide an audible reminder that a turn signal has been left on. Once the warning chime begins to sound, it will continue until the turn signal is cancelled, until the vehicle speed falls below about 24 kilometers-per-hour (15 miles-per-hour), or until the ignition switch is turned to the Off position.

The hard wired circuits of the turn signal and hazard warning system can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the turn signal on warning feature, the EMIC, the CTM, and the PCI data bus must be tested using a DRBIII scan tool.