1988 JEEP CHEROKEE Service Repair Manual

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AU TO T R AN S D IA G NO SIS - A W 4

1988 J e ep C hero ke e
AUTOMATIC TRANSMISSIONS
Aisin Warner 4 Electronic Diagnosis
APPLICATION
NOTE: Transmission may also be referred to as AW-4.
TRANSMISSION APPLICATION









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Vehicle Application Transmission Model
Jeep
1987-96 Cherokee ................................... AW4
1987-92 Comanche ................................... AW4
1987 Grand Wagoneer ................................ AW4
1987-90 Wagoneer ................................... AW4
1992 Wrangler ...................................... AW4









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NOTE: Vehicle body code may be required when diagnosing or
repairing transmission, as body code may be used instead of
vehicle model name. See BODY CODE DESIGNATION table.
BODY CODE DESIGNATION









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Vehicle Model Body Code
Cherokee .............................................. XJ
Comanche .............................................. MJ
Grand Wagoneer ........................................ SJ
Wagoneer .............................................. XJ
Wrangler .............................................. YJ









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DESCRIPTION
The electronic control system for the AW-4 transmission
controls transmission shift points and torque converter lock-up.
Electronic control system consists of Transmission Control Module
(TCM), valve body solenoids, throttle position sensor, speed sensor,
neutral safety switch and brake switch.
NOTE: Transmission Control Module (TCM) may be referred to as
Transmission Control Unit (TCU). Neutral safety switch may
be referred to as park/neutral safety switch or gear select
switch.
OPERATION
TRANSMISSION CONTROL MODULE (TCM)
The TCM determines shift points and torque converter lock-up
based on input signals received from throttle position sensor, neutral
safety switch, speed sensor and brake switch. The TCM controls
transmission shift points and torque converter lock-up by operating
electric solenoids mounted on the valve body.
The TCM contains a self-diagnostic system used for
determining an electronic component failure. The TCM self-diagnostic

system will store a diagnostic trouble code in the TCM memory if
certain electronic problems exist. If electronic problem goes away,
diagnostic trouble code will be erased from TCM memory after ignition
has been cycled approximately 75 times.
NOTE: Diagnostic trouble code may be referred to as fault code.
Diagnostic trouble codes can be retrieved using a Diagnostic
Readout Box-II (DRB-II). After repairing an electrical system problem,\
stored diagnostic trouble code must be cleared from TCM memory.
The TCM is located behind right side of instrument panel on
Cherokee. See Fig. 1.
Fig. 1: Transmission Control Module (TCM) I.D. (Cherokee)
Courtesy of Chrysler Corp.
VALVE BODY SOLENOIDS
Valve body solenoids, mounted on the valve body, are output
devices controlled by signals received from the TCM. See Fig. 2. The
No. 1 and 2 valve body solenoids control transmission shifts while the
No. 3 valve body solenoid is used for torque converter lock-up.
When No. 1 and 2 valve body solenoids are energized,
solenoid plunger moves from seat. This opens the drain port and
releases line pressure. When either valve body solenoid is de-
energized, plunger closes the drain port.
The No. 3 valve body solenoid operates in reverse. When No. 3
valve body solenoid is de-energized, solenoid plunger moves away from
seat. This opens the drain port and releases line pressure. When No. 3
valve body solenoid is energized, the plunger closes the drain port.

NOTE: For valve body solenoid usage, see VALVE BODY SOLENOID
APPLICATION table.
VALVE BODY SOLENOID APPLICATION (1)









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Shift Lever No. 1 No. 2
Position Solenoid Solenoid
"D" (Drive)
1st Gear .................. ON .................... OFF
2nd Gear .................. ON ..................... ON
3rd Gear .................. OFF .................... ON
4th Gear .................. OFF ................... OFF
"3"
1st Gear .................. ON .................... OFF
2nd Gear .................. ON ..................... ON
3rd Gear .................. OFF .................... ON
"1-2"
1st Gear .................. ON .................... OFF
2nd Gear .................. ON ..................... ON
"R" (Reverse) .............. ON .................... OFF
"N" Or "P" ................. ON .................... OFF
( 1) - Valve body contains 3 valve body solenoids. See
Fig. 2. No. 1 and 2 valve body solenoids are used
for controlling transmission shifts. No. 3 valve
body solenoid is used for torque converter
lock-up only.









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Fig. 2: Identifying Valve Body Solenoids
Courtesy of Chrysler Corp.
BRAKE SWITCH

Brake switch is an input device mounted above the brake
pedal. When brake pedal is operated, brake switch delivers an input
signal to the TCM. The TCM uses input signal for controlling No. 3
valve body solenoid for torque converter lock-up.
NEUTRAL SAFETY SWITCH
NOTE: Neutral safety switch may be referred to as park/neutral
safety switch or gear select switch.
Neutral safety switch is an input device mounted on the
transmission manual valve shaft. Neutral safety switch delivers an
input signal to TCM, indicating transmission manual valve gear
position.
SPEED SENSOR
Speed sensor, mounted in adapter housing or extension
housing, is an input device consisting of speed sensor rotor and speed
sensor. Speed sensor rotor is mounted on transmission output shaft.
Input signal is delivered from speed sensor to TCM with each
revolution of transmission output shaft. The TCM uses input signal for
controlling transmission operation.
THROTTLE POSITION SENSOR (TPS)
The TPS, mounted on throttle body, determines throttle
position and delivers an input signal to TCM. The TCM uses input
signal for controlling transmission upshifts and torque converter
lock-up.
SELF-DIAGNOSTIC SYSTEM
DIAGNOSTIC PROCEDURE
When performing vehicle diagnosis:
* Ensure transmission fluid level is correct and fluid is
neither contaminated nor aerated.
* Ensure shift cable is properly adjusted. Refer to the
appropriate TRANSMISSION SERVICING - A/T article in
this section.
* Ensure battery is fully charged.
* Perform visual inspection, ensuring all electrical
connections at transmission, TCM, throttle position sensor,
neutral safety switch, speed sensor and brake switch are
clean and properly installed.
* Perform TEST 1A - VERIFICATION OF THE COMPLAINT under TROUBLE
SHOOTING CHARTS in this article.
* Repair diagnostic trouble codes in order displayed.
* Always perform TEST 2A - VERIFICATION TEST after repair is
completed. See TEST 2A - VERIFICATION TEST under TROUBLE
SHOOTING CHARTS in this article.
RETRIEVING DIAGNOSTIC TROUBLE CODES
NOTE: Manufacturer recommends using Chrysler's Diagnostic Readout
Box-II (DRB-II) with proper cartridge for system diagnosis.
Other after-market scan tools may be used for system
diagnosis. The following procedure is for DRB-II scan tool
usage. Use manufacturer's instruction for operating the

DRB-II scan tool. When retrieving diagnostic trouble codes
using DRB-II, you must first enter AW4 MENU and then
retrieve diagnostic trouble codes.
NOTE: Ensure TEST 1A - VERIFICATION OF THE COMPLAINT is performed
when trouble shooting the vehicle. This test checks for
diagnostic trouble codes with vehicle stationary and during
road test. See TEST 1A - VERIFICATION OF THE COMPLAINT under
TROUBLE SHOOTING CHARTS.
NOTE: The DRB-II scan tool can be used in several different modes
using manufacturer's instructions to activate system
components and perform several tests on transmission. See
DRB-II OPERATING MODES .
Entering AW4 MENU
1) Ensure ignition is off. Connect DRB-II to 6-pin
transmission diagnostic connector. See Fig. 3. Transmission diagnostic
connector is located to the right of the steering column on driver's
side of instrument panel above accelerator pedal or below glove box on
passenger's side.
Fig. 3: Diagnostic Connector & Terminals I.D. (Cherokee)
Courtesy of Chrysler Corp.
2) Turn ignition on. Copyright date and diagnostic program
will be briefly displayed. If DRB-II displays an error message,
proceed to DRB-II PROBLEMS & ERROR MESSAGES . The following are
possible error messages that may appear.

* CARTRIDGE ERROR
* HIGH BATTERY
* KEYPAD TEST FAILURE
* LOW BATTERY
* RAM TEST FAILURE
3) If no error messages appear, display will read as follows
after a few seconds: 1) VEHICLES TESTED, 2) HOW TO USE, 3) CONFIGURE
and 4) SELECT SYSTEM.
4) Select 4) SELECT SYSTEM to enter diagnostic system. Once
in SELECT SYSTEM, select 2) TRANSMISSION to enter transmission.
Display will read 1) EATX and 2) AW4.
5) Select 2) AW4. After a few seconds display will change to
read AW4, VERSION 01. After a few seconds, display will read AW4 MENU,
1) SYSTEM TEST and 2) READ FAULTS. If DOWN ARROW is depressed 3 times,\
display will read as follows: 3) STATE DISPLAY, 4) ACTUATOR TESTS and
5) ADJUSTMENTS.
NOTE: The ACTUATOR TESTS and ADJUSTMENTS cannot be used when
diagnosing the AW-4 transmission.
Retrieving Diagnostic Trouble Codes
1) Select 2) READ FAULTS from AW4 MENU. If no diagnostic
trouble code exists, display will read as follows: AW4 FAULTS, NO
FAULTS DETECTED.
2) If diagnostic trouble code exists, the following message
will be displayed: 1 OF 3 FAULTS. This number will vary depending on
number of diagnostic trouble codes stored in the TCM memory.
3) Diagnostic trouble code and message will be displayed.
Press DOWN ARROW key to display next diagnostic trouble code. To
identify diagnostic trouble code, see DIAGNOSTIC TROUBLE CODE
IDENTIFICATION table.
NOTE: See TROUBLE SHOOTING CHARTS to diagnose faults indicated by
trouble codes.
NOTE: Valve body solenoid diagnostic trouble code 700 may appear
in a FAULT PRESENT or FAULT STORED status. Status will be
displayed along with diagnostic trouble code. Diagnostic
trouble code must be diagnosed depending on the status. See
TEST 1A - VERIFICATION OF THE COMPLAINT under TROUBLE
SHOOTING CHARTS.
DIAGNOSTIC TROUBLE CODE IDENTIFICATION









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Trouble Code Problem Area
700 ( 1) .............................. Valve Body Solenoid
702 ......................................... Speed Sensor
703 ............................... ( 2) Gear Select Switch
705 ............................. Throttle Position Sensor
706 ......................................... Brake Switch
707 ..................................... Wrong TCM Or TCU
( 1) - Trouble code may apply to individual valve body
solenoids. Valve body solenoid may be referred to
as S1 for No. 1, S2 for No. 2 and S3 for No. 3.
( 2) - Gear select switch is the same as the neutral
safety switch.









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CLEARING DIAGNOSTIC TROUBLE CODES

1) Once all diagnostic trouble codes have been obtained,
diagnostic trouble code(s) can be erased from TCM memory by
disconnecting electrical connector from TCM for at least 15 seconds.
CAUTION: DO NOT disconnect battery, as data stored in other vehicle
control modules will be lost.
2) The TCM is located behind right side of instrument panel
on Cherokee. See Fig. 1.
DRB-II OPERATING MODES
NOTE: The DRB-II can be operated in several different modes to
perform various tests. Except for voltmeter/ohmmeter and HOW
TO USE modes, all other operating modes are selected from
AW4 MENU. See ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC
TROUBLE CODES.
VOLTMETER/OHMMETER MODE
To access voltmeter/ohmmeter mode, connect Red volt-ohmmeter
test lead to Red port at top right corner of DRB-II. There are 2
different ports on top of DRB-II; ensure test lead is connected to
proper port. Access voltmeter or ohmmeter mode using manufacturer's
instructions.
NOTE: The DRB-II is grounded through transmission diagnostic
connector and only one test lead is required. When
diagnosing transmission, an external volt-ohmmeter may
sometimes be required.
HOW TO USE MODE
1) This mode gives instructions on DRB-II usage. To enter
this mode, see steps 1) through 4) of ENTERING AW4 MENU under
RETRIEVING DIAGNOSTIC TROUBLE CODES . Select 2) HOW TO USE.
2) A series of screens will be displayed explaining DRB-II
key usage for system diagnosing.
SYSTEM TEST MODE
NOTE: SYSTEM TEST mode consists of a stationary test and a road
test. The SYSTEM TEST mode must be selected from AW4 MENU.
See ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC TROUBLE
CODES.
1) Stationary test monitors transmission system data, current
valve body solenoid failures, switch failures, correct TCM
application, calibration and operation. Road test checks all valve
body solenoids and speed sensor.
2) Technician will be instructed to place shift lever in each
gear position, starting by shifting into 1-2 position. Once
transmission is in Park, brake pedal must be depressed to check brake
switch.
3) After brake switch is checked, technician will be
instructed to slowly depress throttle. DRB-II will display 7 asterisks
( ******* ) corresponding to throttle position. While depressing
accelerator, Throttle Position Sensor (TPS) sweeps through entire
range of positions required by the TCM.
4) A corresponding asterisk will be cleared from DRB-II
display as each throttle position is sensed by TCM. Several attempts
may be required to clear all asterisks from the display, depending on

how fast accelerator is depressed.
5) After throttle position is checked, technician will be
instructed to drive the vehicle. The DRB-II will indicate if a
requested action is seen by the TCM. If technician is requested to
perform a particular operation and TCM does not acknowledge the
action, press ENTER key to continue testing.
6) The TCM will instruct technician to accelerate vehicle at
light throttle to ensure transmission shifts through all gears,
indicating proper valve body solenoid operation.
7) During road test, ensure vehicle can be accelerated slowly
and evenly to allow transmission to enter all gear ranges without
downshifting or braking. If a failure is sensed, a diagnostic trouble
code will be displayed on DRB-II.
NOTE: If TCM senses a failure, control logic activates a specified
valve body solenoid to obtain a certain gear depending on
failure. Because transmission diagnostic trouble codes are
displayed one at a time, multiple diagnostic trouble codes
must be identified by retesting transmission.
STATE DISPLAY MODE
NOTE: STATE DISPLAY mode must be selected from AW4 MENU. See
ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC TROUBLE CODES .
Select 3) STATE DISPLAY on DRB-II.
Module Information
When selecting module information option, the TCM version
will be indicated by a 2-digit number. Information can be used to
verify proper TCM application.
Sensor
1) When selecting sensor option, TPS and RPM indications will
be shown. The TPS indicator will display a 7 segment bar graph,
indicating TPS position and throttle plate angle.
2) A properly operating TPS should indicate 7 segments
through full throttle travel. The RPM indicator will display
transmission output shaft revolutions per minute.
Brake Switch Or Input/Output
Display indicates brake switch status, indicating whether
brake pedal is applied or released. Display also indicates shift lever
position, whether a valve body solenoid is on or off and present
transmission operating gear.
DRB-II PROBLEMS & ERROR MESSAGES
CARTRIDGE ERROR
1) If CARTRIDGE ERROR message is displayed, disconnect DRB-II
from transmission diagnostic connector. DO NOT touch keys on DRB-II
keypad. Reconnect DRB-II to transmission diagnostic connector and note
display.
2) If CARTRIDGE ERROR message is displayed, replace DRB-II
cartridge and proceed with diagnostics. If KEYPAD TEST FAILURE message
is displayed, replace DRB-II and proceed with diagnostics.
HIGH BATTERY
If HIGH BATTERY message is displayed, use external voltmeter
to check battery voltage at battery terminals. If battery voltage is
11.7-13.0 volts, replace DRB-II. If battery voltage is not 11.7-13.0