Jeep Cherokee (XJ): Description and operation
DESCRIPTION A turn signal system is standard factory-installed
safety equipment on this model. The turn signal system
uses ignition switched battery current, and will
operate only when the ignition switch is in the On or
Accessory positions. The turn signal system includes
the following components: Refer to Lamp in the proper section of Group 8L -
Lamps for more information on the exterior turn signal
lamps. Refer to Instrument Cluster in the
proper section of Group 8E - Instrument Panel Systems
for more information on the turn signal indicator
lamps. Following are general descriptions of the
major components in the turn signal system. For
complete circuit diagrams, refer to Turn Signals in
the Contents of Group 8W - Wiring Diagrams. OPERATION With the ignition switch in the On or Accessory
position, and the turn signal (multi-function) switch
control stalk 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
lamp, front park/turn signal lamp, front side marker
lamp and rear tail/stop/turn signal lamp to flash on
and off. If the exterior lamps are turned off, the front
park/turn signal lamp and the front side marker
lamp will flash in unison. If the exterior lamps are
turned on, the front park/turn signal lamp and the
front side marker lamp will flash alternately.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of the turn signal system. DESCRIPTION A hazard warning system is standard factory-installed
safety equipment on this model. Unlike the
turn signal system, the hazard warning system uses
a non-switched source of battery current so that the
system will operate regardless of the ignition switch
position. The hazard warning system includes the following
components: Refer to Lamp in the proper section of Group 8L -
Lamps for more information on the exterior turn signal
lamps. Refer to Instrument Cluster in the
proper section of Group 8E - Instrument Panel Systems
for more information on the turn signal indicator
lamps. Following are general descriptions of the
major components in the hazard warning system. For
complete circuit diagrams, refer to Turn Signals in
the Contents of Group 8W - Wiring Diagrams. OPERATION With the hazard warning 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 indicator lamps, front park/turn signal
lamps, front side marker lamps and rear tail/stop/
turn signal lamps to flash on and off. 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.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of the hazard warning system. DESCRIPTION The turn signal and hazard warning switches are
integral to the multi-function switch unit, which is
secured to the left side of the steering column (Fig.
1). The only visible parts of the multi-function switch
are the control stalk that extends from the left side
of the steering column, and the hazard warning
switch button that protrudes from the top of the
steering column. The multi-function switch control
stalk has international control symbols on it, which
identify its functions. The hazard warning switch
button is identified with a double triangle, which is
the international control symbol for hazard warning.
The remainder of the multi-function switch is concealed
beneath the steering column shrouds.
The multi-function switch also contains circuitry
for the following functions: The information contained in this group addresses
only the multi-function switch turn signal and hazard
warning functions. For information relative to
the other systems that are controlled by and circuits
that are integral to the multi-function switch, see the
group in this service manual that covers that system.
However, the turn signal and hazard warning
switches cannot be repaired. If these switches or any
other circuit or component of the multi-function
switch unit is faulty or damaged, the entire multifunction
switch unit must be replaced.
1 - HAZARD WARNING BUTTON OPERATION TURN SIGNAL SWITCH The multi-function switch control stalk that
extends from the left side of the steering column just
below the steering wheel is moved up or down to
activate the turn signal switch. When the control
stalk is moved in the upward direction, the right
turn signal switch circuitry is activated; and, when
the control stalk is moved in the downward direction,
the left turn signal switch circuitry is activated. The
turn signal switch has a detent position in each
direction that provides turn signals with automatic
cancellation, and an intermediate momentary position
in each direction that provides turn signals only
until the multi-function switch control stalk is
released.
When the turn signal switch is in a detent position,
it is turned off by one of two turn signal cancelling
cam lobes that are integral to the rotor of the
clockspring mechanism. Turning the steering wheel
causes the turn signal cancelling cam lobes to contact
a cancel actuator in the multi-function switch, and
the turn signal switch automatically returns to the
off position. HAZARD WARNING SWITCH The hazard warning switch is controlled by the
hazard warning switch button. Slide the switch button
to the left to turn the switch on and activate the
hazard warning system, and slide the button to the
right again to turn the switch and the hazard warning
system off. DESCRIPTION The turn signal cancelling cam is concealed within
the steering column below the steering wheel. The
turn signal cancelling cam consists of two lobes that
are integral to the lower surface of the clockspring
rotor. The clockspring mechanism provides turn signal
cancellation as well as a constant electrical connection
between the horn switch, driver side airbag
module and speed control switches on the steering
wheel and the instrument panel wire harness on the
steering column. The housing of the clockspring is
secured to the steering column and remains stationary.
The rotor of the clockspring, including the turn
signal cancelling cam lobes rotate with the steering
wheel.
The turn signal cancelling cam is integral to the
clockspring and cannot be repaired. If faulty or damaged,
the entire clockspring assembly must be
replaced. Refer to Clockspring in the Removal and
Installation section of Group 8M - Passive Restraint
Systems for the clockspring service procedures. OPERATION The turn signal cancelling cam has two lobes
molded into the lower surface 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 clockspring rotor. When the
steering wheel is rotated during the turn, one of the
two turn signal cancelling cam lobes will contact the
turn signal cancel actuator, releasing the multi-function
switch control stalk from its detent and cancelling
the turn signal event. DESCRIPTION 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.
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.
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 circuits
as described in this group. Then replace the
combination flasher with a known good unit to confirm
system operation.
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. Refer to Turn
Signals in the Contents of Group 8W - Wiring Diagrams
for complete circuit diagrams.
The combination flasher is located in a wire harness
connector which is secured to the diagnostics
splice block bracket outboard of the steering column
opening underneath the instrument panel. The combination
flasher cannot be repaired or adjusted and,
if faulty or damaged, it must be replaced. OPERATION The IC within the combination flasher (Fig. 2) 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 multifunction
switch. When the hazard warning switch is
turned on, the 9hazard 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-perminute
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.Turn signal system
Hazard warning system
Turn signal switch and hazard
warning switch
Fig. 1 Multi-Function Switch
2 - CANCEL ACTUATOR
3 - CONTROL STALKTurn signal cancelling cam
Combination flasher
Fig. 2 Combination Flasher - Typical
Other materials:
Brake/Transmission Shift Interlock System. Nine-Speed Automatic Transmission. Gear Ranges
Brake/Transmission Shift Interlock System
This vehicle is equipped with a Brake Transmission Shift
Interlock system (BTSI) that holds the shift lever in PARK
unless the brakes are applied. To shift the transmission
out of PARK, the ignition must be turned to the ON/
RUN position (engine running ...