Part 3 of 3
HAZARD SWITCHThe hazard switch is activated by a push button located in the multifunction switch on the top of the steering column between the steering wheel and instrument cluster.
The hazard warning system allows the vehicle operator to provide other vehicle operators in the near proximity an optical indication that the vehicle is disabled or an obstacle to traffic flow. The hazard warning system has battery voltage at all times, regardless of ignition position.
The instrument cluster monitors the multiplexed multifunction switch operation. When the hazard warning switch is activated, the instrument cluster will send a J1850 bus message to the Front Control Module (FCM), then activate the two turn signal indicators and audible click in the instrument cluster.
The FCM will then activate the necessary relays in the Power Distribution Center (PDC) to begin flashing both the front and rear turn signal indicator lamps.
HEADLAMP SWITCH
The multiplexed headlamp switch is located on the instrument panel. The headlamp switch controls the parking lamps, fog lamps and the headlamps. A separate switch in the module controls the interior lamps and instrument cluster illumination. This switch also contains a rheostat for controlling the illumination level of the cluster lamps.
The multiplexed headlamp switch has an OFF, parking lamp, fog lamp and a headlamp on position. High beams are controlled by the multiplexed multifunction switch on the steering column. The fog lamps are illuminated by pulling back on the headlamp switch knob when in the parking lamp or headlamp ON position. The headlamp switch cannot be repaired. It must be replaced.
The Instrument Cluster monitors the headlamp and multifunction switch operation. When the headlamp switch is rotated to the parking lamp or ON position the Instrument Cluster sends a J1850 message to the Front Control Module, which is mated to the power distribution center to become the Integrated Control Module, to illuminate the appropriate bulbs. When the multifunction switch is activated to the optical horn or high beam position the Instrument Cluster illuminates the high beam indicator and sends a J1850 message to the Front Control Module to illuminate the appropriate bulbs.
MULTI-FUNCTION SWITCH
Turn Signal System
The multi-function switch is a resistive MUX switch that is monitored by the Instrument Cluster. The turn signals are actuated with the lever on Multi-Function Switch. The signals are automatically turned OFF by a canceling cam (two lobes molded to the back of the clock spring mechanism). The cam comes in contact with the cancel actuator on the turn signal (multi-function) switch assembly. Either cam lobe, pushing on the cancel actuator, returns the switch to the OFF position.
The Instrument Cluster monitors the multiplexed multifunction switch. In a turning event the Instrument Cluster senses a change in the turn signal lever and illuminates the appropriate turn signal indicator. At the same time, the Instrument Cluster will send a J1850 message on the PCI bus to the Front Control Module (FCM). The FCM will respond by activating the appropriate relay in the Power Distribution Center.
A chime will sound after the turn is completed if vehicle has traveled a distance of approximately 1.0 mile and a speed of 15 mph, with the turn signal ON.
Fig.11 ISO Micro Relay:
PARK LAMP RELAY
The park lamp relay is located in the Power Distribution Center (PDC) of the vehicle. The park lamp relay is a conventional International Standards Organization (ISO) micro relay. Relays conforming to the ISO specifications have common physical dimensions, current capacities, terminal patterns, and terminal functions.
The park lamp relay cannot be adjusted or repaired and, if faulty or damaged, the unit must be replaced.
The park lamp relay is an electromechanical switch that uses a low current input from the Front Control Module (FCM) to control a high current output to the park lamps. The movable common feed contact point is held against the fixed normally closed contact point by spring pressure. When the relay coil is energized, an electromagnetic field is produced by the coil windings. This electromagnetic field draws the movable relay contact point away from the fixed normally closed contact point, and holds it against the fixed normally open contact point. When the relay coil is de-energized, spring pressure returns the movable contact point back against the fixed normally closed contact point. A resistor is connected in parallel with the relay coil in the relay, and helps to dissipate voltage spikes and electromagnetic interference that can be generated as the electromagnetic field of the relay coil collapses.
The park lamp relay terminals are connected to the vehicle electrical system through a connector in the Junction Block (JB). The inputs and outputs of the headlamp low beam relay include:
- Common Feed Terminal - The common feed terminal (30) is connected to the park lamps through the park lamp relay output circuit and provides ground to the park lamps when the relay is de-energized, and battery current to the park lamps whenever the relay is energized.
- Coil Ground Terminal - The coil ground terminal (85) is connected to a control output of the Front Control Module (FCM) through a park lamp relay control circuit. The FCM controls park lamp operation by controlling a ground path through this circuit.
- Coil Battery Terminal - The coil battery terminal (86) receives battery current at all times from a fuse in the PDC through a fused B(+) circuit.
- Normally Open Terminal - The normally open terminal (87) receives battery current at all times from a fuse in the Power Distribution Center (PDC) through a fused B(+) circuit.
- Normally Closed Terminal - The normally closed terminal (87A) is connected to ground at all times.
The park lamp relay can be diagnosed using conventional diagnostic tools and methods.
Fig. 17 Trailer Tow Wiring:
TRAILER TOW WIRING
Vehicles equipped with an optional factory-installed trailer towing package have a rear body wire harness that includes an integral trailer tow wiring take out that connects to a heavy duty, sealed, 7-pin trailer tow connector located in the rear bumper. This harness includes an adapter harness that adapts the 7-pin trailer tow connector to a standard, light-duty, 4-pin trailer tow connector. Refer to the appropriate wiring information.