Jeep Liberty KJ. Manual - part 97

BRAKE LAMP SWITCH

DESCRIPTION

The brake lamp switch (2) is a three circuit, spring-
loaded plunger actuated switch that is secured to the
steering column support bracket under the instrument
panel on the driver side of the vehicle. The molded
plastic switch housing has an integral connector
receptacle (1) containing six terminal pins and featur-
ing a Connector Position Assurance (CPA) lock. The
switch is connected to the vehicle electrical system
through a dedicated take out of the instrument panel
wire harness.

The switch plunger (3) extends through a mounting collar (4) on one end of the switch housing. The plunger has a
one time telescoping self-adjustment feature that is activated after the switch is installed by moving an adjustment
release lever (5) on the opposite end of the switch housing clockwise, until it locks into a position that is parallel to
the connector receptacle.

An installed brake lamp switch cannot be readjusted or repaired. If the switch is damaged, inoperative, or removed
from its mounting position for any reason, it must be replaced with a new unit.

OPERATION

The brake lamp switch controls three independent circuits. These circuits are described as follows:

•

Brake Lamp Switch Circuit - A normally open brake lamp switch circuit receives a battery voltage input, and
supplies this battery voltage to the brake lamps and the Controller Antilock Brake (CAB) on a brake lamp
switch output circuit only when the brake pedal is depressed (brake lamp switch plunger released).

•

Brake Lamp Switch Signal Circuit - A normally closed brake lamp switch signal circuit receives a direct path
to ground, and supplies this ground input to the Powertrain Control Module (PCM) on a brake lamp switch
sense circuit only when the brake pedal is released (brake lamp switch plunger is depressed).

•

Speed Control Circuit - A normally closed speed control circuit receives a battery voltage input from the Pow-
ertrain Control Module on a speed control supply circuit, and supplies this battery voltage to the speed control
servo solenoids (dump, vacuum, and vent) on a speed control brake switch output circuit only when the speed
control system is turned On and the brake pedal is released (brake lamp switch plunger is depressed).

The components of the self-adjusting brake switch plunger consist of a two-piece telescoping plunger, a split plunger
locking collar, and a release wedge. The release lever has a shaft with a wedge that spreads the plunger locking
collar to an open or released position. After the switch is installed and the brake pedal is released, the plunger
telescopes to the correct adjustment position. When the release lever is moved to the release position, the wedge
is disengaged from the locking collar causing the collar to apply a clamping pressure to the two plunger halves,
fixing the plunger length.

The brake lamp switch can be diagnosed using conventional diagnostic tools and methods.

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LAMPS/LIGHTING - EXTERIOR

DIAGNOSIS AND TESTING

BRAKE LAMP SWITCH

WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.

CAUTION: Do not remove the brake lamp switch from the mounting bracket. The self-adjusting switch
plunger is a one time only feature. If the switch is removed from the mounting bracket, it MUST be replaced
with a new switch.

1. Disconnect and isolate the battery negative cable.

2. Disconnect the wire harness connector from the

brake lamp switch.

3. Using an ohmmeter, perform the continuity tests at

the terminal pins (1) in the brake lamp switch con-
nector receptacle as shown in the Brake Lamp
Switch Tests table.

BRAKE LAMP SWITCH TESTS

PLUNGER POSITION (2)

CONTINUITY BETWEEN

(1)

Released (Extended)

Pins 1 and 2

Compressed (Depressed)

Pins 3 and 4, 5 and 6

4. If the switch fails any of the continuity tests, replace the inoperative brake lamp switch as required.

REMOVAL

CAUTION: The brake lamp switch self-adjusting switch plunger is a one time only feature. If the switch is
removed from the mounting bracket, it MUST be replaced with a new switch.

LAMPS/LIGHTING - EXTERIOR

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1. Disconnect and isolate the battery negative cable.

2. Locate the brake lamp switch (4) near the support

bracket (1) on the lower steering column.

3. Disconnect the wire harness connector (2) from the

brake lamp switch.

4. Rotate the brake lamp switch housing counter-

clockwise about 30 degrees to align the tabs on
the switch locking collar with the keyed mounting
hole in the switch mounting bracket.

5. Pull the switch straight back from the keyed hole to

remove it from the bracket.

6. Discard the removed brake lamp switch.

INSTALLATION

CAUTION: The brake lamp switch self-adjusting switch plunger is a one time only feature. If the switch is
removed from the mounting bracket, it MUST be replaced with a new switch.

1. Depress and hold the brake pedal (5) in the

depressed position.

2. Align the tabs on the brake lamp switch (4) locking

collar with the keyed hole in the switch mounting
bracket.

3. Insert the tabs on the brake lamp switch locking

collar through the keyed hole in the switch mount-
ing bracket until the switch housing is firmly seated
against the bracket.

4. Rotate the switch clockwise about 30 degrees to

engage the tabs on the locking collar with the
switch mounting bracket.

5. Release the brake pedal.

CAUTION: Do not release or pull up on the brake
pedal before the switch plunger adjustment has
been completed.

6. Release the brake pedal, but do not pull it upward.

7. Rotate the plunger adjustment release lever (3) clockwise until it locks into place. The lever should be parallel to

the brake lamp switch connector receptacle. This action will set the switch plunger length to a final adjustment
position and cannot be undone. If not performed properly the first time, a new brake lamp switch must be
installed.

8. Reconnect the wire harness connector (2) to the brake lamp switch.

9. Reconnect the battery negative cable.

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LAMPS/LIGHTING - EXTERIOR

LAMP-HIGH MOUNTED STOP

REMOVAL

BULB

1. Disconnect and isolate the battery negative cable.

2. Remove the two screws that secure the Center

High Mounted Stop Lamp (CHMSL) (1) to the roof
panel.

3. Pull the CHMSL lens and housing away from the

header panel far enough to access the lamp wiring
(4) and bulb socket (3) on the back of the lamp.

4. Firmly grasp the socket on the back of the lamp

housing and rotate it counterclockwise about 30
degrees to unlock it.

5. Pull the socket and bulb (2) straight out from the

keyed opening in the housing.

6. Pull the base of the bulb straight out of the socket.

LAMP

1. Disconnect and isolate the battery negative cable.

2. Remove the two screws (5) that secure the Center

High Mounted Stop Lamp (CHMSL) (4) to the rear
of the roof panel (1).

3. Pull the CHMSL away from the roof panel far

enough to access and disconnect the wire harness
connector (4) from the lamp socket (3).

4. Remove the CHMSL from the roof panel.

INSTALLATION

BULB

CAUTION: Always use the correct bulb size and type for replacement. An incorrect bulb size or type may
overheat and cause damage to the lamp, the socket and/or the lamp wiring.

LAMPS/LIGHTING - EXTERIOR

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