Turn Signals: Description and Operation
TURN SIGNAL & HAZARD WARNING SYSTEMA turn signal and hazard warning system is standard factory-installed safety equipment on this model. 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 - The electronic combination flasher is installed in a dedicated connector of the instrument panel wire harness located under the instrument panel outboard of the steering column opening.
- Hazard Warning Switch - The hazard warning switch is integral to the multi-function switch on the left side of the steering column. The hazard warning switch button protrudes from a dedicated opening in the shroud on the top of the steering column, just below the steering wheel.
- Turn Signal Cancel Cam - The turn signal cancel cam is integral to the clockspring, which is located beneath the steering column shrouds at the top of the steering column, just below the steering wheel.
- Turn Signal Indicators - The two turn signal indicators, one right and one left, are integral to the ElectroMechanical Instrument Cluster (EMIC) located in the instrument panel.
- Turn Signal Lamps - The front turn signal lamps are integral to the lower front outboard ends of the headlamp modules, located just outboard of the two sides of the radiator grille opening. The rear turn signal lamps are integral to the taillamp modules that are secured to the quarter panels at each side of the liftgate opening.
- Turn Signal Switch - The turn signal switch is integral to the multi-function switch on the left side of the steering column. The multi-function switch control stalk that actuates the turn signal switch protrudes from a dedicated opening in the steering column shrouds on the left side of the column, just below the steering wheel.
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 km/h (15 mph) for a distance of greater than about 1.6 kilometers (1 mile). (Refer to INSTRUMENT CLUSTER - DESCRIPTION).
Hard wired circuitry connects the turn signal and hazard warning system components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the turn signal and hazard warning system components through the use of a combination of soldered splices, splice block connectors and many different types of wire harness terminal connectors and insulators.
The turn signal system operates on battery current 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 current received on a fused B(+) circuit so that the hazard warning remains operational regardless of the ignition switch position. When the turn signal (multi-function) switch control stalk is moved up (right turn) or down (left turn), the turn signal system is activated. 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, and rear tail/stop/turn signal lamp to flash ON and OFF. With the hazard warning (multi-function) switch in the ON position, the hazard warning system is activated. 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, 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 km/h (15 mph), the EMIC generates an electronic chime request message to the Central Timer Module (CTM) over the PCI data bus. The CTM then generates an audible chime tone through its integral chime tone generator 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 (either manually or mechanically), until the vehicle speed falls below about 24 km/h (15 mph), or until the ignition switch is turned to the OFF position, whichever occurs first.
The hard wired circuits of the turn signal and hazard warning system can be diagnosed using conventional diagnostic tools and methods; however, for proper diagnosis of the turn signal on warning feature, the EMIC, the CTM, and the PCI data bus must be tested using a DRB III scan tool. Refer to the appropriate diagnostic information. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of the turn signal and hazard warning system.
TURN SIGNAL CANCEL CAM
The turn signal cancel cam is concealed within the steering column below the steering wheel. The turn signal cancel cam consists of two lobes on a molded plastic ring that is snapped into the lower hub of the clockspring rotor. The clockspring mechanism provides turn signal cancellation as well as a constant electrical connection between the horn switch, driver airbag, speed control switches, and remote radio switches on the steering wheel and the instrument panel wire harness on the steering column. The housing of the clockspring is secured to the multi- function switch mounting housing on the steering column and remains stationary. The rotor of the clockspring, including the turn signal cancel cam lobes rotate with the steering wheel.
The turn signal cancel cam is serviced as a unit with the clockspring and cannot be repaired. If faulty or damaged, the entire clockspring unit must be replaced. (Refer to CLOCKSPRING - REMOVAL).
The turn signal cancel cam has two lobes and is secured to the lower hub opening of the clockspring rotor. When the turn signals are activated by moving the multi-function switch control stalk to a detent position, a turn signal cancel actuator is extended from the inside surface of the multi-function switch housing toward the center of the steering column and the turn signal cancel cam. When the steering wheel is rotated during a turning maneuver, one of the two turn signal cancel cam lobes will contact the turn signal cancel actuator. The cancel actuator latches against the cancel cam rotation in the direction opposite that which is signaled. In other words, if the left turn signal detent is selected, the lobes of the cancel cam will ratchet past the cancel actuator when the steering wheel is rotated to the left, but will unlatch the cancel actuator as the steering wheel rotates to the right and returns to center, which will cancel the turn signal event and release the control stalk from the detent so it returns to the neutral OFF position.