Jeep XJ. Manual — part 883
1.0
INTRODUCTION
The procedures contained in this manual include
specifications, instructions, and graphics needed to
diagnose the AW4 AUTOMATIC TRANSMISSION.
The diagnostics in this manual are based on the
failure condition or symptom being present at the
time of diagnosis.
Please follow the recommendations below when
choosing your diagnostic path.
1. First make sure the DRBIII
t is communicating
with the appropriate modules; ie., if the DRBIII
t
displays a “No Response” condition, you must
diagnose this first before proceeding.
2. Read DTC’s (diagnostic trouble codes) with the
DRBIII
t.
3. If no DTC’s are present, identify the customer
complaint.
4. Once the DTC or customer complaint is identi-
fied, locate the matching test in the Table of
Contents and begin to diagnose the symptom.
All component location views are in Section 8.0.
All connector pinouts are in Section 9.0. All system
schematics are in section 10.0.
An * placed before the symptom description indi-
cates a customer complaint.
When repairs are required, refer to the appropri-
ate service manual for the proper removal and
repair procedure.
Diagnostic procedures change every year. New
diagnostic systems may be added; carryover sys-
tems may be enhanced. READ THIS MANUAL
BEFORE TRYING TO DIAGNOSE A VEHICLE
CODE. It is recommended that you review the
entire manual to become familiar with all new and
changed diagnostic procedures.
After using this book, if you have any comments
or recommendations, please fill out the form at the
back of the book and mail it back to us.
1.1
SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the AW4 electronic transmission
system is done in six basic steps:
•
verification of complaint
•
verification of any related symptoms
•
symptom analysis
•
problem isolation
•
repair of isolated problem
•
verification of proper operation
2.0
IDENTIFICATION OF
SYSTEM
All 2001 Jeep Cherokees (XJ) vehicles equipped
with a 4.0 liter engine and automatic transmission
have an AW4 electronic transmission.
3.0
SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1
GENERAL DESCRIPTION
The AW4 electronic transmission is a conven-
tional transmission in that it uses hydraulically
applied clutches to shift a planetary gear train.
However, the electronic control system replaces
many of the mechanical and hydraulic components
used in conventional transmission valve bodies.
The AW4 transmission control system has im-
proved significantly since it’s introduction. The
Park/Neutral switch was replaced by a Transmis-
sion Range Sensor (TRS). The Transmission Con-
trol Module (TCM) now has the ability to commu-
nicate with the Powertrain Control Module (PCM)
via the CCD Bus. The TCM also has the ability to
monitor transmission faults which could affect
emissions. Any transmission fault which will ad-
versely affect emissions will set a DTC in the PCM
and will also illuminate the MIL.
An Input Speed Sensor (ISS) was added to the
control system. This gives improved functional
trouble detection. This results in a new Diagnostic
Trouble Code (DTC) to detect ISS malfunctions. The
“Solenoid A or TCC Solenoid Functional Fault” DTC
was separated into two DTC’s “Shift solenoid A
functional fault” and “TCC solenoid C functional
fault” and there was also a new DTC for internal
TCM failures.
3.2
FUNCTIONAL OPERATION
The AW4 system performs it’s functions based on
continuous real-time sensor feedback information.
The Transmission Control Module (TCM) continu-
ously checks for electrical problems, some mechan-
ical problems, and some hydraulic problems. When
a problem is sensed, the TCM stores a diagnostic
trouble code. Some of these codes cause the trans-
mission to go into “limp-in” or “default” mode. While
in this mode, the TCM may not energize some of the
solenoids in the transmission.
The only transmission functions that may be
available are:
•
Park and Neutral
•
Reverse
1
GENERAL INFORMATION
•
Fourth Gear (Gear Selector OD Position)
•
Third Gear (Gear Selector 3 Position)
•
First Gear (Gear Selector 1-2 Position)
Depending on the DTC that is set, determines
what gear(s) are allowed. If one or more of the
transmission solenoids are shorted to voltage or
stuck open (therefore appearing energized to the
transmission), the transmission may be stuck in the
gear that would normally be engaged when a par-
ticular solenoid is energized.
The following chart shows the solenoid status
required for a particular gear to be engaged.
Sol #A
Sol #B
Gear
Off
On
1st
On
On
2nd
On
Off
3rd
Off
Off
4th
Although vehicle performance may be seriously
degraded while in this mode (limp-in), it allows the
owner to drive the vehicle in for service.
3.3
DIAGNOSTIC TROUBLE CODES
(DTC’S)
Always begin diagnosis by performing a visual
inspection,
– check the fluid level and condition and correct
as necessary
– check and adjust manual linkage as necessary
– check the electrical connections at the PCM,
TCM, TPS, TRS and Transmission solenoids
for pushed out or corroded terminals. Make
sure all connectors are seated properly.
– test drive the vehicle to verify the customer
complaint
– read the DTC’s, the DTC will direct you to the
specific test(s) in the table of contents that
must be performed. If more than one code
exists, diagnostic priority should be given to
the most recent code.
If there is a CCD bus or communication problem,
trouble codes will not be accessible until the prob-
lem is repaired. The DRBIII
t will display an appro-
piate diagnostic message.
The following is a possible list of causes for a bus
problem:
– open in either or both CCD bus wires.
– short to ground on either or both CCD bus
wires.
– short to battery on either or both CCD bus
wires.
– internal failure of any module or component on
the bus
NOTE:
THE
CCD
BUS
SHOULD
HAVE
APPROXIMATELY
2.5
VOLTS
ON
BOTH
WIRES. FOR MORE DETAILED INFORMATION
ABOUT DIAGNOSING CCD BUS PROBLEMS,
REFER
TO
THE
APPROPRIATE
BODY
DIAGNOSTIC SYMPTOM.
The P-code, P1698−No CCD messages from
TCM has been added in 1997.
This is a powertrain symptom (PCM code) and is
diagnosed in powertrain diagnostics symptoms.
Each diagnostic trouble code is diagnosed by follow-
ing a testing sequence. The diagnostic test procedures
contain step-by-step instructions for determining the
cause of a transmission diagnostic trouble code. Pos-
sible sources of the code are checked and eliminated
one by one. It is not necessary to perform all of the
tests in this book to diagnose an individual code. In
certain test procedures within this book, codes are
used as a diagnostic tool.
DTC’s which affect vehicle emissions will illumi-
nate the Malfunction Indicator Lamp (MIL). Three
consecutive “Good” OBDII trips or clearing the
DTC’s with a diagnostic tool (DRBIII
t or equiva-
lent) is required to extinguish the MIL.
3.3.1
HARD CODE
Any Diagnostic trouble codes (or One-Trip failure
or drive cycle) that comes back within one cycle of the
ignition key is a “hard” code. This means that the
problem is there every time the TCM checks that
circuit or function.
NOTE: NOT ALL OBDII CODES WILL NOT
SET WITH JUST THE IGNITION KEY ON.
THEY MUST BE DRIVEN, IN THE VEHICLE
START AND DRIVE CYCLE(S) SUCH THAT
ALL DIAGNOSTIC MONITORS HAVE RUN.
3.3.2
INTERMITTENT CODE
A diagnostic trouble code that is not present every
time the TCM checks the circuit or function is an
“intermittent” code. Problems that come and go like
this are the most difficult to diagnose, they must be
looked for under the specific conditions that cause them.
3.3.3
STARTS SINCE SET COUNTER
For the most recent code (Code 1), the starts since
set counter count the number of times the vehicle
has started since it was last set. The starts since set
counter will count up to 255 starts. When there are
no diagnostic trouble codes stored in memory, the
DRBIII
t will display “NO DTC’s DETECTED”.
If DTC’s are detected, the DRBIII
t will display
the number of good trips. This is the number of good
trips since the latest DTC was set. The number of
2
GENERAL INFORMATION
good trips helps determine if the diagnostic trouble
code is hard or intermittent.
– If the Good Trip count is displayed and equal
to 0, the code is a hard code.
Note: Look at “One-Trip” codes as a Hard
codes.
– If the code is in the Warm-Up Cycle counter, it is
considered an intermittent code. This means that
the vehicle (transmission) has been driven at
least “3 Good Trips” without the code recurring.
3.3.4
TROUBLE CODE ERASURE
A Diagnostic trouble code will be cleared from
TCM memory if 40 Warm-Up Cycles have occured.
A warm-up cycle is defined by CARB as “sufficient
vehicle operation such that the coolant temperature
has risen by at least 40°F from engine starting and
reaches a minimum temperature of 160°F”.
The Malfunction Indicator Lamp (MIL) will turn
off after 3 good trips. The MIL will also turn off if
the DTC’s are cleared from the TCM with the
diagnostic scan tool or if the problem corrects itself.
3.3.5
LIST OF DIAGNOSTIC TROUBLE
CODES
The TCM may report any of the following DTC’s.
Scan
Name of Code
P0122
THROTTLE POSITION SENSOR SIG-
NAL CIRCUIT
P0562
TRANSMISSION VOLTAGE LOW
P0563
TRANSMISSION VOLTAGE HIGH
P0705
CHECK SHIFTER SIGNAL (RANGE
SENSOR)
P0715
INPUT SPEED SENSOR
P0720
OUTPUT SPEED SENSOR
P0740
(TCC) SOLENOID C FUNCTIONAL
FAULT
P0751
SOLENOID A FUNCTIONAL FAULT
P0756
SOLENOID B FUNCTIONAL FAULT
P1694
NO CCD MESSAGE FROM PCM
P1718
INTERNAL TCM (EEPROM)
P1742
INTERNAL TCM (ROM)
P1743
INTERNAL TCM (RAM)
P1744
SOLENOID A SHORTED TO GROUND
P1745
SOLENOID A SHORTED TO VOLTAGE
OR OPEN
P1746
SOLENOID B SHORTED TO GROUND
P1747
SOLENOID B SHORTED TO VOLTAGE
OR OPEN
P1748
(TCC) SOLENOID C SHORTED TO
GROUND
P1749
(TCC) SOLENOID C SHORTED TO
VOLTAGE OR OPEN
The P-codes, P1698-” No CCD messages from
TCM”
and
P0700
“Transmission
Fault
Present” are Powertrain Symptoms (PCM
codes) and are diagnosed under the power-
train diagnostic symptoms group.
DTC’s for AW4 transmission controller are not
permanent and will change the moment the reason
for the code is corrected.
3.4
INPUT SPEED SENSOR
The TCM uses the Input Speed Sensor (ISS) to
detect transmission solenoid functional faults (P0751
solenoid A functional fault, P0756 solenoid B func-
tional fault, TCC solenoid C functional fault). The ISS
is a variable reluctance sensor. Changes in the reluc-
tance of a magnetic circuit caused by the passing of the
rotor lobes on the overdrive clutch drum result in the
ISS outputting an AC periodic voltage wave form. The
frequency and voltage of the wave form are propor-
tional to the transmission input speed.
NOTE: SINCE THE OD/CLUTCH DRUM IS
STATIONARY IN 4TH GEAR OR WHEN THE
VEHICLE IS IN GEAR, BUT NOT MOVING.
THERE WILL BE NO ISS SENSOR SIGNAL.
3.5
OUTPUT SPEED SENSOR
The Transmission Control Module (TCM) uses
the Output Speed Sensor (OSS) to determine shift
points and TCC engagement points. The OSS is a
variable reluctance sensor. Changes in the reluc-
tance of a magnetic circuit caused by the passing of
the rotor lobes on the output shaft result in the OSS
outputting an AC periodic voltage wave form. The
frequency and voltage of the wave form are propor-
tional to the transmission output shaft speed.
3.6
TRANSMISSION RANGE SENSOR
The transmission range sensor (TRS) contacts are
used to determine the position of the shift lever and
also to control the reverse lamps. The TCM determines
the shift lever position based on the table below.
Shift lever position
Range Switch states
R
D
D3
L
P
off
off
off
off
R
on
off
off
off
N
off
off
off
off
OD
off
on
off
off
3
off
off
on
off
1-2
off
off
off
on
3
GENERAL INFORMATION
There are five switches in the TRS, 1 each for the
1-2, 3, OD, Reverse and Park/Neutral. The Park/
Neutral portion of the TRS is hard wired to the
Powertrain Control Module (PCM). The Park/
Neutral information is received by the TCM from
the PCM over the CCD communication bus. 12 volts
is supplied to the TRS through the fused ignition
switch output circuit. The TCM senses this voltage
when a switch is closed. When the reverse switch is
closed, power is supplied to the reverse lamps.
3.7
THROTTLE POSITION SENSOR
The TCM uses the Throttle Position Sensor (TPS)
signal to determine shift points. The TPS circuit is
hard wired to the TCM. If Pcode P0122 “Throttle
Position Sensor circuit” is present, there may be
a TPS code stored in the PCM. Always repair the
PCM throttle position sensor DTC’s first.
3.8
TRANSMISSION CONTROL MODULE
SYSTEM
3.8.1
COMMUNICATIONS TO PCM
The PCM is continuously sending Bus Messages
to the TCM. The TCM requires inputs from the
PCM primarily to determine the Vehicle speed,
Engine RPM, and the Park/Neutral switch state.
The PCM also monitors the CCD bus messages from
the TCM. A Diagnostic code is set if the TCM does
not receive any valid messages from the PCM for 20
seconds.
3.8.2
OPERATING VOLTAGE
The TCM can operate normally with a battery
voltage input between 10.0 and 17.7 volts. If the
battery voltage supply (Fused B+) voltage is out of
range there is a possibility of abnormal operation
and/or TCM failure. A “Transmission Voltage High”
or “Transmission Voltage Low” DTC will be set.
NOTE: ALWAYS PERFORM DIAGNOSTICS
WITH A FULLY CHARGED BATTERY TO
AVOID DIAGNOSING FALSE SYMPTOMS.
3.8.3
SHIFT SOLENOIDS
Two solenoids are used to control shifting. Sole-
noid A is used to control the 1-2 shift and the 3-4
shift. Solenoid B is used to control the 2-3 shift.
Solenoid C controls the operation of the Torque
Converter Clutch (TCC). The TCC solenoid is con-
trolled by the TCM. The TCC can be engaged in
2nd, 3rd and fourth gear. The TCC can not be
engaged in 1st gear, because it is hydraulically
locked out in 1st gear. If the TCM turns off the
solenoids and a voltage is detected on the control
circuit a DTC will be set.
3.8.4
FUNCTIONAL FAULTS
Functional faults are detected by the transmis-
sion control module. The TCM uses the output
speed sensor and the input speed sensor to calculate
the current gear ratio. If the gear ratio is not within
tolerance (within 10%) for the correct gear detected,
a DTC will be set. The TCC solenoid functional fault
will set if the difference between engine RPM and
transmission input RPM is not consistent with the
requested TCC state.
3.9
USING THE DRBIII
T
The TCM and other components have the ability
to interface over the communications bus. The
DRBIII
t Scan Tool connects to the Data Link Con-
nector located in the passenger compartment. This
allows communication with the TCM.
Refer to the DRBIII
t user’s guide for instructions
and assistance with reading trouble codes, erasing
trouble codes, and other DRBIII
t functions.
3.9.1
DRBIII
T ERROR MESSAGES
Under normal operation, the DRBIII
t will dis-
play one of only two error messages:
– User-Requested WARM Boot
– User-Requested COLD Boot
If the DRBIII
t should display any other error
message, record the entire display and call the MDS
Hotline, This is a Sample of such an error message
display:
ver: 2.14
date: 26 Jul93
file: key_itf.cc
date: Jul 26 1998
line: 548
err: 0x1
User-Requested COLD Boot
Press MORE to switch between this display
and the application screen.
Press F4 when done noting information.
3.9.2
DRBIII
T DOES NOT POWER UP
(BLANK SCREEN)
If the LED’s do not light or no sound is emitted at
start up, check for loose cable connections or a bad
cable. Check the vehicle battery voltage. A mini-
mum of 11 volts is required to adequately power the
DRBIII
t.
If all connections are proper between the
DRBIII
t and the vehicle or other devices, and the
4
GENERAL INFORMATION
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