JEEP YJ 1995 Service And Repair Manual

USING ON-BOARD DIAGNOSTIC SYSTEM
The Powertrain Control Module (PCM) monitors
critical input and output circuits of the speed control
system, making sure they are operational. A Diagnos-
tic Trouble Code (DTC) is assigned to each input and
output circuit monitored by the OBD system. Some
circuits are checked continuously and some are
checked only under certain conditions.
If the OBD system senses that a monitored circuit
is bad, it will put a DTC into electronic memory. The
DTC will stay in electronic memory as long as the
circuit continues to be bad. The PCM is programmed
to clear the memory after 50 engine starts, if the
problem does not occur again.
DIAGNOSTIC TROUBLE CODES
Diagnostic Trouble Codes (DTC) are two-digit num-
bers flashed on the malfunction indicator (Check En-
gine) lamp that identify which circuit is bad. A DTC
description can also be read using the DRB scan tool.
Refer to Group 14 - Fuel Systems for more informa-
tion.
A DTC does not identify which component in a cir-
cuit is bad. Thus, a DTC should be treated as a
symptom, not as the cause for the problem. In some
cases, because of the design of the diagnostic test
procedure, a DTC can be the reason for another DTC
to be set. Therefore, it is important that the test pro-
cedures be followed in sequence, to understand what
caused a DTC to be set.
See Speed Control Diagnostic Trouble Code chart
for DTC's which apply to the speed control system.Refer to the Powertrain Diagnostic Procedures man-
ual to diagnose an on-board diagnostic system trou-
ble code.
RETRIEVING DIAGNOSTIC TROUBLE CODES
To start this function, cycle the ignition switch ON-
OFF-ON-OFF-ON within 5 seconds. This will cause
any DTC stored in the PCM memory to be displayed.
The malfunction indicator (Check Engine) lamp will
display a DTC by flashing on and off. There is a
short pause between flashes and a longer pause be-
tween digits. All DTC's displayed are two-digit num-
bers, with a four-second pause between codes.
An example of a DTC is as follows:
(1) Lamp on for 2 seconds, then turns off.
(2) Lamp flashes 1 time pauses and then flashes 5
times.
(3) Lamp pauses for 4 seconds, flashes 3 times,
pauses, then flashes 4 times.
The two DTC's are 15 and 34. Any number of
DTC's can be displayed, as long as they are in mem-
ory. The lamp will flash until all stored DTC's are
displayed (55 = end of test).
If a DTC 15 is observed, see diagnosis for Vehicle
Speed Sensor in this group. If a DTC 34 is observed,
see diagnosis for Speed Control Servo and Power-
train Control Module in this group. Correct any prob-
lems found in your diagnosis, then recheck for DTC
after corrections are completed.
VEHICLE SPEED SENSOR
For diagnosis of the VSS, refer to the appropriate
Powertrain Diagnostic Procedures manual.
SPEED CONTROL DIAGNOSTIC TROUBLE CODE
JVEHICLE SPEED CONTROL SYSTEM 8H - 5

SPEED CONTROL SWITCH
WARNING: ON VEHICLES EQUIPPED WITH AN AIR-
BAG, REFER TO GROUP 8M - RESTRAINT SYS-
TEMS BEFORE ATTEMPTING STEERING WHEEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE PROPER PRECAUTIONS COULD RESULT
IN ACCIDENTAL AIRBAG DEPLOYMENT AND POS-
SIBLE PERSONAL INJURY.
(1) Disconnect battery negative cable. Remove
speed control switch from steering wheel.
(2) Check speed control switch continuity as shown
in chart (Fig. 2). If OK, reinstall switch. If not OK,
replace switch.
STOP LAMP SWITCH
(1) Unplug the connector at the stop lamp switch.
With the brake pedal released, check switch for con-
tinuity at the switch side of connector (Fig. 3) as fol-
lows:
(a) There should be continuity between the black
and white/pink wires.
(b) There should be continuity between the yel-
low/red and dark blue/red wires.
(c) There should be no continuity between pink
and white wires.(2) With the brake pedal applied, check switch for
continuity at the switch side of connector (Fig. 3) as
follows:
(a) There should be continuity between pink and
white wires.
(b) There should be no continuity between black
and white/pink wires.
(c) There should be no continuity between the
yellow/red and dark blue/red wires.
(3) If the above results are not obtained, check the
stop lamp switch adjustment. If adjustment is OK,
replace faulty switch. Refer to Group 5 - Brakes for
adjustment and service procedures.
VACUUM SUPPLY TEST
(1) Disconnect vacuum hose at the servo and in-
stall a vacuum gauge in the hose.
(2) Start engine and observe gauge at idle. Vacuum
gauge should read at least ten inches of mercury.
(3) If vacuum does not meet this requirement,
check for vacuum leaks or poor engine performance.
SPEED CONTROL SERVO
(1) Check fuse F13 in the PDC. If OK, go to next
step. If not OK, replace fuse.
(2) Turn ignition switch to the ON position. Check
for battery voltage at fuse F13. If OK, go to next
step. If not OK, repair open circuit to ignition switch
as required.
(3) Connect the negative lead of a voltmeter to a
good chassis ground near the servo. Unplug the
4-way connector going to the servo (Fig. 4 or 5). Push
the speed control switch to the ON position. Check
for battery voltage at servo harness connector cavity
Fig. 2 Speed Control Switch Continuity
Fig. 3 Stop Lamp Switch Connector
8H - 6 VEHICLE SPEED CONTROL SYSTEMJ

for pin 2 (Fig. 6). If OK, go to next step. If not OK,
see diagnosis for Stop Lamp Switch.
(4) Connect a jumper wire between servo harness
connector cavity for pin 2 and pin 2 of the servo.
Check for battery voltage at pins 1, 3 and 4 of the
servo. If OK, go to next step. If not OK, replace the
servo.
(5) Turn ignition switch to OFF position. Check for
continuity between servo harness connector cavity for
pin 1 and a good ground. There should be continuity.
If not OK, repair open circuit to ground as required.
POWERTRAIN CONTROL MODULE
(1) Disconnect 60-way connector from the PCM, lo-
cated on the dash panel near the wiper motor in the
engine compartment (Fig. 7).(2) Connect negative lead of voltmeter to a good
body ground near the module.
(3) For the following tests, the ignition switch
must be in the ON position. See Fig. 8 for controller
terminal locations. Touch the positive lead of the
voltmeter to the terminal in cavity number 33. With
the speed control switch in the OFF position, the
voltmeter should read zero volts. With the speed con-
trol switch in the ON position, the voltmeter should
read battery voltage. If not, repair the main harness
as necessary.
(4) Touch the positive lead of the voltmeter to the
terminal in cavity number 53. As in step (3), the volt-
meter should read zero volts with the switch in the
OFF position, and battery voltage with the switch in
the ON position.
(5) Touch the positive lead of the voltmeter to the
terminal in cavity number 48. With the speed control
switch in the OFF position, the voltmeter should
Fig. 4 Speed Control Servo - LHD
Fig. 5 Speed Control Servo - RHD
Fig. 6 Servo Harness Connector
Fig. 7 Powertrain Control Module
JVEHICLE SPEED CONTROL SYSTEM 8H - 7

read zero volts. With the switch in the ON position,
the voltmeter should read battery voltage. Pressing
the SET/COAST button should cause the voltmeter to
change from battery voltage to zero volts for as long
as the switch is held. If not, perform the Speed Con-
trol Switch Test. If the switch is not at fault, then
check the main harness and repair as necessary.
(6) Touch the positive lead of the voltmeter to the
terminal in cavity number 50. The voltmeter should
read zero volts with the speed control switch in ei-
ther the OFF or ON position. With switch in eitherRESUME or SET position, the voltmeter should read
battery voltage. If not, perform the Speed Control
Switch Test. If the switch is not at fault, then check
the main harness and repair as necessary.
(7) Touch the positive lead of the voltmeter to the
terminal in cavity number 49. The voltmeter should
read zero volts with the switch in the OFF position.
With the switch in the ON position, the voltmeter
should read battery voltage. The voltmeter will con-
tinue to read battery voltage when either the SET or
RESUME switch is pressed. If not, perform the
Speed Control Switch Test. If the switch is not at
fault, then check the main harness and repair as nec-
essary.
(8) Turn ignition switch OFF. Using an ohmmeter,
connect one lead to a good body ground and touch the
other lead to the terminal in cavity number 29. With
the brake pedal released, the meter should show con-
tinuity. When the pedal is depressed, the meter
should show an open circuit.
Fig. 8 PCM 60-Way Connector - Terminal End
8H - 8 VEHICLE SPEED CONTROL SYSTEMJ

SERVICE PROCEDURES
SPEED CONTROL SERVO REMOVE/INSTALL
(1) Disconnect battery negative cable.
(2) Disconnect vacuum hose at servo.
(3) Remove 2 nuts on servo cable sleeve.
(4) Pull speed control cable away from servo to ex-
pose cable retaining clip (Fig. 9).
(5) Remove clip attaching cable to servo.
(6) Pull servo away from mounting bracket.
(7) To install, insert servo studs through holes in
sevo mounting bracket.
(8) Block throttle to full open position, align hole
in cable sleeve with hole in servo pin and install re-
taining clip.
(9) Reverse remaining removal procedures to in-
stall. Tighten servo mounting nuts to 6 Nzm (50 in.
lbs.).
SPEED CONTROL SWITCH REMOVE/INSTALL
WARNING: ON VEHICLES EQUIPPED WITH AN AIR-
BAG, REFER TO GROUP 8M - RESTRAINT SYS-
TEMS BEFORE ATTEMPTING STEERING WHEEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE PROPER PRECAUTIONS COULD RESULT
IN ACCIDENTAL AIRBAG DEPLOYMENT AND POS-
SIBLE PERSONAL INJURY.
(1) Disconnect negative cable from battery.
(2) From underside of steering wheel, remove
speed control switch mounting screws (Fig. 10).
(3) Pull switches from wheel and unplug connector.
(4) Plug electrical connector into new switches.
(5) Install new switches with 2 screws.
Fig. 9 Servo Cable Remove/Install
Fig. 10 Speed Control Switch Remove/Install -
Typical
JVEHICLE SPEED CONTROL SYSTEM 8H - 9

SERVO CABLE REMOVE/INSTALL
(1) Remove air cleaner.
(2) Using finger pressure only, remove speed con-
trol cable connector at bellcrank by pushing connec-
tor off the bellcrank (Fig. 11). DO NOT try to pull
connector off perpendicular to the bellcrank.(3) Squeeze tabs on speed control cable and push
out of locking plate (Fig. 12). Unclip cable from cable
guide.
(4) Remove servo cable from servo as described in
Speed Control Servo Remove/Install.
(5) Reverse removal procedures to install.
VACUUM RESERVOIR REMOVE/INSTALL
(1) Remove vacuum hose connection at reservoir.
(2) Remove 2 screws securing reservoir from be-
neath front bumper.
(3) Remove reservoir.
(4) Reverse removal procedures to install. Tighten
mounting screws to 8.5 Nzm (75 in. lbs.).
Fig. 11 Servo Cable to Bellcrank Remove/Install
Fig. 12 Servo Cable to Locking Plate Remove/Install
8H - 10 VEHICLE SPEED CONTROL SYSTEMJ

TURN SIGNAL AND HAZARD WARNING SYSTEMS
CONTENTS
page page
DIAGNOSIS............................. 3
GENERAL INFORMATION.................. 1SERVICE PROCEDURES................... 5
GENERAL INFORMATION
Following are general descriptions of the major
components in the XJ (Cherokee)/YJ (Wrangler)
model turn signal and hazard warning systems. Refer
to Group 8W - Wiring Diagrams for complete circuit
descriptions and diagrams.
TURN SIGNAL SYSTEM
With the ignition switch in the ON or ACCESSORY
position and the turn signal switch lever (YJ) or
multi-function switch control lever (XJ) moved up
(right turn) or down (left turn), the turn signal sys-
tem is activated.
When the turn signal system is activated, the se-
lected (right or left) turn signal indicator lamp, front
park/turn signal lamp and rear tail/stop/turn signal
lamp bulb filaments will flash. With the headlamp
switch in the OFF position, the turn and front side
marker lamps flash in unison. With the headlamp
switch in the ON position, the turn and front side
marker lamps flash alternately.
HAZARD WARNING SYSTEM
The hazard warning is activated by a switch button
located below the ignition lock cylinder (YJ) or on the
top of the steering column (XJ) between the steering
wheel and the instrument panel. The hazard warning
flasher (YJ) or combination flasher (XJ) receives bat-
tery feed at all times, and the system is functional
regardless of ignition switch position. The hazard
warning switch button is identified with a double
triangle. On YJ models, push the switch button in to
activate the hazard warning system and pull the
button out to turn system off. On XJ models, push in
on the switch button to latch the switch and activate
the hazard warning system, and push in on the
switch button again to unlatch the switch and turn
the system off.
When the hazard warning system is activated, all
(right and left) turn signal indicator, front park/turn
signal lamp and rear tail/stop/turn signal lamp bulb
filaments will flash.
TURN SIGNAL FLASHER (YJ ONLY)
The turn signal flasher is located in the fuseblock
module. It contains one fixed contact point and one
contact point attached to a flexible bimetal arm. The
contact points are normally closed. When a turn sig-
nal is activated, current flows through the flasher. As
current flows through the bimetal arm it heats and
flexes to pull the contact points open, stopping cur-
rent flow. As the bimetal arm cools it straightens,
until the contact points close and the cycle repeats.
The standard flasher is designed to handle the cur-
rent flow requirements of the factory installed light-
ing. If supplemental lighting is added to the turn
signal circuits such as when towing a trailer with
lights, the current flow through the flasher increases.
This causes the flash rate to increase. It is recom-
mended that the standard flasher be replaced with a
heavy-duty (hazard warning) flasher when supple-
mental lighting is added.
However, when a turn signal bulb fails with a stan-
dard flasher, the remaining bulbs in that circuit will
light, but not flash. This will give the driver an indi-
cation to check the turn signal bulbs. Because a
heavy-duty flasher has different internal circuitry, a
failed bulb will not prevent the remaining bulbs in
the circuit from flashing. Therefore, it is recom-
mended that an occasional visual inspection of exte-
rior turn signal lamp operation be performed when a
heavy-duty flasher is installed.
HAZARD WARNING FLASHER (YJ ONLY)
The hazard warning flasher is located in the fuse-
block module. The hazard warning flasher contains
two normally open contact points mounted to two
flexible arms. A bimetal strip is attached between the
two arms. When the hazard warning is activated,
current flows through the flasher. As the current
flows through the bimetal strip it heats and pulls the
flexible arms together until the contact points close,
JTURN SIGNAL AND HAZARD WARNING SYSTEMS 8J - 1

allowing current flow to the lamps. As the bimetal
strip cools, the contact points are pushed open and
the cycle repeats.
COMBINATION FLASHER (XJ ONLY)
The combination flasher functions as both the turn
signal and hazard warning flasher on XJ models. The
combination flasher is a smart relay that is located in
the relay center under the lower instrument panel
and inboard of the steering column. The combination
flasher can not be repaired. If faulty, it must be
replaced.
The combination flasher is designed to handle the
current flow requirements of the factory installed
lighting. If supplemental lighting is added to the turn
signal circuits such as when towing a trailer with
lights, the combination flasher will automatically
compensate. This allows the flash rate to remain the
same, regardless of electrical load increases. However,
if a bulb fails in the turn signal or hazard warning
circuits, the flash rate of the remaining bulbs in that
circuit will increase to 120 flashes per minute or
higher.
TURN SIGNAL/HAZARD WARNING SWITCH
(YJ ONLY)
The turn signal and hazard warning switches are
combined into a single unit mounted within the upper
steering column bowl and beneath the steering wheel.
The turn signal lever on the left side of the steering
column is moved up or down to select the right or left
turn signal switch position. The turn signals will only
operate with the ignition switch in the ACCESSORY
or ON position.
The hazard warning button on the right side of the
steering column is pushed in to turn the hazard
warning system on, or pulled out to turn the system
off. The hazard warning system will operate regard-
less of ignition switch position. The turn signal/haz-
ard warning switch can not be repaired. If faulty, the
entire unit must be replaced.
MULTI-FUNCTION SWITCH (XJ ONLY)
The multi-function switch assembly (Fig. 1) is
mounted to the left side of the steering column. This
switch contains electrical circuitry for the following
functions:²turn signals
²hazard warning
²headlamp beam selection
²headlamp optical horn
²windshield wipers
²windshield washers.
The information contained in this group addresses
only the switch functions for the turn signal and
hazard warning circuits. For information relative to
other switch functions, refer to the appropriate group.
However, the multi-function switch can not be re-
paired. If any function of the switch is faulty, the
entire switch assembly must be replaced.
TURN SIGNAL INDICATOR LAMPS
These lamps are located in the instrument cluster.
They flash with the exterior turn signal lamps to give
the driver a visual indication that a turn signal or the
hazard warning circuit is operating. For diagnosis
and service of this component, refer to Group 8E -
Instrument Panel and Gauges.
TURN SIGNAL LAMPS
The exterior lamps included in the turn signal and
hazard warning circuits include: the front park/turn
signal, and the rear tail/stop/turn signal. For diagno-
sis and service of these lamps, refer to Group 8L -
Lamps.
Fig. 1 Multi-Function Switch
8J - 2 TURN SIGNAL AND HAZARD WARNING SYSTEMSJ

DIAGNOSIS
When diagnosing the turn signal or hazard warning
circuits, remember that high generator output can
burn out bulbs rapidly and repeatedly. If this is a
problem on the vehicle being diagnosed, refer to
Group 8A - Battery/Starting/Charging Systems Diag-
nostics to test charging system.
WARNING: ON VEHICLES EQUIPPED WITH AN AIR-
BAG, REFER TO GROUP 8M - RESTRAINT SYS-
TEMS BEFORE ATTEMPTING STEERING WHEEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE PROPER PRECAUTIONS COULD RESULT
IN ACCIDENTAL AIRBAG DEPLOYMENT AND POS-
SIBLE PERSONAL INJURY.
TURN SIGNAL/HAZARD WARNING SYSTEM - XJ
(1) Turn ignition switch to ON position. Actuate the
turn signal lever or hazard warning button. Observe
the turn indicator lamp(s) in the instrument cluster.
If the flash rate is very high, check for a turn signal
bulb that is not lit. Replace that bulb or repair cir-
cuits to that lamp, as required. Test operation. If turn
indicator does not light, continue to next step.
(2) Remove and inspect fuse 8 (turn signals) in
fuseblock module, or fuse F13 (hazard warning) in the
Power Distribution Center. Replace fuse, if required.
(3) Remove combination flasher from relay center
and replace with a known good unit. Test operation of
turn signal and hazard warning systems. If OK, re-place faulty combination flasher. If not OK, remove
test flasher and go to next step.
(4) With ignition switch in ON position, check for
battery voltage at cavity for flasher terminal J1 (Fig.
2). If OK, go to next step. If not OK, repair circuit to
ignition switch as required.
(5) With ignition switch in OFF position, check for
battery voltage at cavity for flasher terminal J2. If
OK, go to next step. If not OK, repair circuit to Power
Distribution Center as required.
(6) With ignition switch in OFF position, check for
continuity between cavity for flasher terminal J5 and
a good ground. There should be continuity. If OK, go
to next step. If not OK, repair circuit to ground as
required.
(7) Locate the multi-function switch connector. See
Multi-Function Switch, in this group. Check for conti-
nuity between cavity for flasher terminal J3 and cav-
ity 13 of the multi-function switch connector. There
should be continuity. If OK, go to next step. If not OK,
repair open circuit as required.
(8) Check for continuity between cavity for flasher
terminal J4 and cavity 17 of the multi-function switch
connector. There should be continuity. If OK, test
multi-function switch. If not OK, repair open circuit
as required.
TURN SIGNAL SYSTEM - YJ
A turn signal indicator lamp that remains lit (with-
out flashing) is an indication of a burned out exterior
turn signal bulb or faulty exterior lamp circuit. Check
Fig. 2 Combination Flasher Circuit - XJ
JTURN SIGNAL AND HAZARD WARNING SYSTEMS 8J - 3

lamps and repair circuits or replace bulbs as re-
quired. If system still does not function properly, pro-
ceed as follows.
(1) Locate fuseblock module under driver's side of
instrument panel. Remove and inspect fuse 4. If OK,
go to next step. If not OK, replace fuse as required.
(2) Replace turn signal flasher (light blue can in
fuseblock module) with a known good unit. Test op-
eration. If OK, replace faulty turn signal flasher. If
not OK, remove test flasher and go to next step.
(3) Turn ignition switch to ACCESSORY position.
Check for battery voltage at flasher cavity on left
(closest to hazard flasher). If OK, go to next step. If
not OK, repair circuit to fuse 4 as required.
(4) Turn ignition switch to OFF position. See Turn
Signal/Hazard Warning Switch Remove/Install to lo-
cate steering column connector. Unplug connector.
(5) Turn ignition switch to ACCESSORY position.
Check for battery voltage at connector terminal L. If
OK, replace turn signal/hazard warning switch. If not
OK, repair circuit between turn signal flasher and
steering column connector.
HAZARD WARNING SYSTEM - YJ
(1) Locate Power Distribution Center (PDC) near
battery tray in engine compartment. Remove and in-
spect fuse F5. If OK, go to next step. If not OK,
replace fuse as required.(2) Replace hazard warning flasher (metal can in
fuseblock module) with a known good unit. Test op-
eration. If OK, replace faulty hazard warning flasher.
If not OK, remove test flasher and go to next step.
(3) Check for battery voltage at flasher cavity on
left (closest to hazard flasher). If OK, go to next step.
If not OK, repair circuit to fuse F5 in PDC as re-
quired.
(4) See Turn Signal/Hazard Warning Switch Re-
move/Install to locate steering column connector. Un-
plug connector.
(5) Check for battery voltage at connector terminal
K. If OK, replace turn signal/hazard warning switch.
If not OK, repair circuit between hazard warning
flasher and steering column connector.
MULTI-FUNCTION SWITCH - XJ
(1) Access multi-function switch connector and re-
move. See service procedures for Multi-Function
Switch, in this group.
(2) Using an ohmmeter, perform switch continuity
checks at the switch terminals as shown in the chart
(Fig. 3).
Fig. 3 Multi-Function Switch Continuity
8J - 4 TURN SIGNAL AND HAZARD WARNING SYSTEMSJ