Turn Signals: Description and Operation

TURN SIGNAL & HAZARD WARNING 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
- Front Side Marker Lamps
- Hazard Warning Switch
- Turn Signal Cancel Cam
- Turn Signal Indicators
- Turn Signal Lamps
- Turn Signal Switch

The turn signal and hazard warning systems also provide the following features:
- Flash Lights with Lock - This customer programmable feature flashes the hazard warning lamps to provide optical verification that the Remote Keyless Entry (RKE) System has received a valid Lock or Unlock request from an RKE transmitter.
- Panic Mode Optical Alert - This feature flashes the hazard warning lamps to provide an optical alert when the Remote Keyless Entry (RKE) System panic mode is activated by depressing the Panic button on an RKE transmitter.
- Turn Signal On Warning - This feature provides the vehicle operator with both visual and audible reminders when a turn signal has been left turned on for an extended period.
- Vehicle Theft Security System (VTSS) Optical Alarm - This feature flashes the hazard warning lamps to provide an optical alarm when the VTSS is armed and activated by an unauthorized entry into the vehicle.

Some vehicles are equipped with a remote headlamp leveling system. This system allows the driver to adjust the headlamp beam pattern from the interior of the vehicle to compensate for passenger or cargo load. Only the vertical axis of the headlamp beam can be adjusted.

A headlamp leveling switch is located on the instrument panel and controls the headlamp leveling motors/modules found on the headlamp modules. Leveling switch has four settings 0-3, 0 being the lowest, 3 being the highest headlight beam vertical setting.

When performing a headlamp beam pattern alignment on a vehicle equipped with headlamp leveling, be certain the headlamp leveling switch is in the "0" position before starting. Failure to do so will result in and incorrect headlamp alignment.

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

The Body Control Module (BCM) can also activate the hazard warning system lamps by energizing the combination flasher through a single hard wired connection to the hazard warning switch sense circuit. The BCM grounds the circuit to energize and de-energize the combination flasher in response to message inputs received over the Programmable Communications Interface (PCI) data bus network. The BCM can energize the combination flasher when the VTSS is requested.

Vehicles equipped with the optional Electronic Vehicle Information Center (EVIC) use turn signal status messages received from the Electro-Mechanical Instrument Cluster (EMIC) and distance messages received from the Powertrain Control Module (PCM) over the PCI data bus to determine when the Turn Signal On warning should be activated. The EMIC receives hard wired inputs from the combination flasher to operate the turn signal indicators, then sends the proper turn signal status message to the EVIC. If a turn signal is left on for more than about 1.6 kilometers (1 mile) of driving distance, the EVIC will display a visual "Turn Signal On" message and will send a request to the BCM over the PCI data bus to notify the vehicle operator.

During both the turn signal and the hazard warning operation, if the exterior lamps are turned Off, the front park/turn signal lamps and the front side marker lamps will flash in unison. If the exterior lamps are turned On, the front park/turn signal lamps and the front side marker lamps will flash alternately.

Upon moving the headlamp leveling switch control knob, voltage is adjusted at the headlamp leveling switch (rheostat). This signals the headlamp leveling motors to move and adjust the vertical headlamp beam pattern accordingly. The headlamps must be "on" in order for the leveling system to function. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.