Part 1 of 2
LAMPS/LIGHTING - EXTERIORTurn Signal & Hazard Warning System
A 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 the Junction Block (JB), which is located behind the fuse access panel on the left outboard end of the instrument panel.
- 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 located on either side of the vehicle. For pickup models the taillamp modules are secured to the rear of the quarter panels at each side of the tailgate opening. For cab and chassis models the taillamp modules are secured by a stamped steel bracket on the outboard side of each frame rail near the rear of the vehicle.
- 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.
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 nonswitched 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.
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.
BRAKE LAMP SWITCH
The plunger type brake lamp switch is mounted on a bracket attached to the brake pedal support under the instrument panel.
CAUTION: The switch can only be adjusted during initial installation. It the switch is not adjusted properly a new switch must be installed.
The brake lamp switch is used for the brake lamp, speed control brake sensor circuits and electronic brake distribution (EBD). The brake lamp circuit is open until the plunger is depressed. The speed control and brake sensor circuits are closed until the plunger is depressed.
When the brake light switch is activated, the Powertrain Control Module (PCM) receives an input indicating that the brakes are being applied. After receiving this input, the PCM maintains idle speed to a scheduled rpm through control of the Idle Air Control (IAC) motor. The brake switch input is also used to disable vent and vacuum solenoid output signals to the speed control servo.
Vehicles equipped with the speed control option use a dual function brake lamp switch. The PCM monitors the state of the dual function brake lamp switch. Refer to the Brake for more information on brake lamp switch service and adjustment procedures.
The brake switch is equipped with three sets of contacts, one normally open and the other two normally closed (brakes disengaged). The PCM sends a 12 volt signal to one of the normally closed contacts in the brake switch, which is returned to the PCM as a brake switch state signal. With the contacts closed, the 12 volt signal is pulled to ground causing the signal to go low. The low voltage signal, monitored by the PCM, indicates that the brakes are not applied. When the brakes are applied, the contacts open,causing the PCM's output brake signal to go high, disengaging the speed control, cutting off PCM power to the speed control solenoids.
The second set of normally closed contacts supplies 12 volts from the PCM any time speed control is turned ON. Through the brake switch, current is routed to the speed control servo solenoids. The speed control solenoids (vacuum, vent and dump) are provided this current any time the speed control is ON and the brakes are disengaged.
when the driver applies the brakes, the contacts open and current is interrupted to the solenoids. The normally open contacts are fed battery voltage. When the brakes are applied, battery voltage is supplied to the brake lamps.
COMBINATION FLASHER
The combination flasher is located in the Junction Block (JB) behind the fuse access panel on the left outboard end of the instrument panel. The combination flasher is a smart relay that functions as both the turn signal system and the hazard warning system flasher. The combination flasher contains active electronic Integrated Circuitry (IC) elements. This flasher is designed to handle the current flow requirements of the factory-installed lighting. If supplemental lighting is added to the turn signal lamp circuits, such as when towing a trailer with lights, the combination flasher will automatically try to compensate to keep the flash rate the same.
The combination flasher has five blade-type terminals that connect it to the vehicle electrical system through five matching cavities in the receptacle of the JB. while the combination flasher has a International Standards Organization (ISO)-type relay terminal configuration or footprint, the internal circuitry is much different. The combination flasher does not use standard ISO-relay inputs or provide ISO-relay type outputs or functions. The combination flasher should never be substituted for an ISO-relay or replaced with an ISO-relay, or else component and vehicle damage may occur.
The combination flasher cannot be repaired or adjusted and, if faulty or damaged, it must be replaced.
The combination flasher has five blade-type terminals intended for the following inputs and outputs: fused B(+), fused ignition switch output, ground, turn signal circuit, and hazard warning circuit. Constant battery voltage and ground are supplied to the flasher so that it can perform the hazard warning function, and ignition switched battery voltage is supplied for the turn signal function.
Fig.6 Combination Flasher - Typical:
The Integrated Circuitry (IC) within the combination flasher contains the logic that controls the flasher operation and the flash rate. Pin 6 of the IC receives a sense voltage from the hazard warning circuit of the multi-function switch. When the hazard warning switch is turned ON, the "hazard on sense" voltage will become low due to the circuit being grounded through the turn signal bulbs. This low voltage sense signals the IC to energize the flash control Positive-Negative-Positive (PNP) transistor at a pre-calibrated flash rate or frequency. Each time the PNP transistor energizes the hazard warning circuit, the pin 6 "hazard on sense" voltage will become high and the IC signals the PNP transistor to de-energize the circuit. This cycling will continue until the hazard warning switch is turned OFF.
Likewise, pin 8 of the IC receives a sense voltage from the turn signal circuits of the multi-function switch. when the left or right turn signal switch is turned ON, the "turn signal on sense" voltage will become low due to the circuit being grounded through the turn signal bulbs. This low voltage sense signals the IC to energize the flash control PNP transistor at a pre-calibrated flash rate or frequency. Each time the PNP transistor energizes the turn signal circuit, the pin 8 "turn signal on sense" voltage will become high and the IC signals the PNP transistor to de-energize the circuit. This cycling will continue until the right or left turn signal switch is turned OFF.
A special design feature of the combination flasher allows it to "sense" that a turn signal circuit or bulb is not operating, and provide the driver an indication of the condition by flashing the remaining bulbs in the affected circuit at a higher rate (120 flashes-per-minute or higher). Conventional flashers either continue flashing at their typical rate (heavy-duty type), or discontinue flashing the affected circuit entirely (standard-duty type). During turn signal operation, the combination flasher IC compares normal battery voltage input on pin 2 with the shunt resistor voltage input on pin 7. If the IC "senses" that the voltage difference between pin 2 and pin 7 is different than the pre-calibrated value of the IC, it will increase the rate at which it signals the PNP transistor to energize the pin 1 output. Thus, the inoperative half (left or right side) of the turn signal circuit will flash faster.
Because of the active electronic elements within the combination flasher, it cannot be tested with conventional automotive electrical test equipment. If the combination flasher is believed to be faulty, test the turn signal system and hazard warning system. Then replace the combination flasher with a known good unit to confirm system operation. (Refer to LAMPS/LIGHTING - EXTERIOR/TURN SIGNAL & HAZARD WARNING SYSTEM - DIAGNOSIS AND TESTING).
DAYTIME RUNNING LAMP MODULE
The Daytime Running Lights (Headlamps) System is installed on vehicles manufactured for sale in Canada only. A separate module, mounted on the cowl, controls the DRL.
The headlamps are illuminated when the ignition switch is turned to the ON position. The DRL module receives a vehicle-moving signal from the vehicle speed sensor. This provides a constant headlamps-on condition as long as the vehicle is moving. The lamps are illuminated at less than 50 percent of normal intensity.