Jeep Wrangler TJ. Manual — part 278
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Position the Sentry Key Immobilizer Module
(SKIM) (Fig. 11). On models with a manual transmis-
sion, lift the multi-function switch upward off of the
upper steering column housing far enough to insert
the SKIM antenna formation between the ignition
key release button and the multi-function switch
housing.
(2) Slide the SKIM antenna ring around the igni-
tion switch lock cylinder housing, then rotate the
SKIM and its mounting bracket upwards and toward
the steering column.
(3) Align the SKIM mounting bracket clip with the
inboard lower flange of the steering column and,
push upward firmly on the connector end of the
SKIM mounting bracket to engage the clip with the
steering column.
(4) Reconnect the cross body wire harness connec-
tor for the SKIM to the SKIM connector.
(5) On models equipped with a manual transmis-
sion, install and tighten the screws that secure the
multi-function switch assembly to the upper steering
column housing. Tighten the screws to 2 N·m (20 in.
lbs.).
(6) Position both the upper and lower shrouds onto
the steering column (Fig. 10).
(7) Install and tighten the screws that secure the
lower steering column shroud to the upper shroud.
Tighten the screws to 2 N·m (18 in. lbs.).
(8) Move the tilt steering column to the fully
raised position and secure it in place by moving the
tilt release lever back to the locked (up) position.
Fig. 11 Sentry Key Immobilizer Module - Typical
1 - UPPER SHROUD
2 - STEERING COLUMN
3 - WIRE HARNESS CONNECTOR
4 - SENTRY KEY IMMOBILIZER MODULE
5 - IGNITION LOCK CYLINDER
6 - SCREW
7 - LOWER SHROUD
8 - STEERING WHEEL
TJ
ELECTRONIC CONTROL MODULES
8E - 13
SENTRY KEY IMMOBILIZER MODULE (Continued)
(9) Reinstall the steering column opening cover.
(Refer to 23 - BODY/INSTRUMENT PANEL/STEER-
ING COLUMN OPENING COVER - INSTALLA-
TION).
(10) Reconnect the battery negative cable.
NOTE: If the SKIM has been replaced with a new
unit, the Sentry Key Immobilizer System (SKIS)
MUST be initialized before the vehicle can be oper-
ated. (Refer to 8 - ELECTRICAL/VEHICLE THEFT
SECURITY - STANDARD PROCEDURE - SKIS INI-
TIALIZATION).
TRANSMISSION CONTROL
MODULE
DESCRIPTION
The Transmission Control Module (TCM) is a sub-
module within the Powertrain Control Module (PCM)
(2).
The PCM (2) is located on the right side of the
dash panel in the engine compartment (Fig. 12) on
left hand drive vehicles. The PCM is referred to as
the NGC.
The PCM (1) is located on the left side of the dash
panel in the engine compartment (Fig. 13) on right
hand drive vehicles.
OPERATION
The TCM is the controlling unit for all electronic
operations of the transmission. The TCM receives
information regarding vehicle operation from both
direct and indirect inputs, and selects the operational
mode of the transmission. Direct inputs are hard-
wired to, and used specifically by the TCM. Indirect
inputs originate from other components/modules, and
are shared with the TCM via the PCI bus.
Some examples of direct inputs to the TCM are:
• Battery (B+) voltage
• Ignition “ON” voltage
• Transmission Control Relay (Switched B+)
• Throttle Position Sensor
• Crankshaft Position Sensor (CKP)
• Transmission Range Sensor (TRS)
• Pressure Switches (L/R, 2/4, OD)
• Transmission Temperature Sensor (Integral to
TRS)
• Input Shaft Speed Sensor
• Output Shaft Speed Sensor
Some examples of indirect inputs to the TCM
are:
• Engine/Body Identification
• Manifold Pressure
• Target Idle
• Torque Reduction Confirmation
• Speed Control ON/OFF Switch
• Engine Coolant Temperature
• Ambient/Battery Temperature
• Brake Switch Status
• DRBt III Communication
Fig. 12 PCM MOUNTING - LEFT HAND DRIVE
1 - MOUNTING SCREWS (3)
2 - PCM
3 - PCM ELECTRICAL CONNECTORS
Fig. 13 PCM MOUNTING - RIGHT HAND DRIVE
1 - PCM
2 - MOUNTING SCREWS (3)
3 - PCM ELECTRICAL CONNECTORS
8E - 14
ELECTRONIC CONTROL MODULES
TJ
SENTRY KEY IMMOBILIZER MODULE (Continued)
Based on the information received from these var-
ious inputs, the TCM determines the appropriate
shift schedule and shift points, depending on the
present operating conditions and driver demand.
This is possible through the control of various direct
and indirect outputs.
Some examples of TCM direct outputs are:
• Transmission Control Relay
• Solenoids (L/R, 2/4, OD and UD)
• Vehicle Speed (to PCM)
• Torque Reduction Request (to PCM)
Some examples of TCM indirect outputs are:
• Transmission Temperature (to PCM)
• PRNDL Position (to BCM)
In addition to monitoring inputs and controlling
outputs, the TCM has other important responsibili-
ties and functions:
• Storing and maintaining Clutch Volume Indices
(CVI)
• Storing and selecting appropriate Shift Sched-
ules
• System self-diagnostics
• Diagnostic capabilities (with DRBt III scan tool)
NOTE: If the TCM has been replaced, the “Quick
Learn Procedure” must be performed. (Refer to 8 -
ELECTRICAL/ELECTRONIC
CONTROL
MODULES/
TRANSMISSION CONTROL MODULE - STANDARD
PROCEDURE)
CLUTCH VOLUME INDEX (CVI)
An important function of the TCM is to monitor
Clutch Volume Index (CVI). CVIs represent the vol-
ume of fluid needed to compress a clutch pack.
The TCM monitors gear ratio changes by monitor-
ing the Input and Output Speed Sensors. The Input,
or Turbine Speed Sensor sends an electrical signal to
the TCM that represents input shaft rpm. The Out-
put Speed Sensor provides the TCM with output
shaft speed information.
By comparing the two inputs, the TCM can deter-
mine transmission gear position. This is important to
the CVI calculation because the TCM determines
CVIs by monitoring how long it takes for a gear
change to occur (Fig. 14).
Gear ratios can be determined by using the DRB
t
III Scan Tool and reading the Input/Output Speed
Sensor values in the “Monitors” display. Gear ratio
can be obtained by dividing the Input Speed Sensor
value by the Output Speed Sensor value.
For example, if the input shaft is rotating at 1000
rpm and the output shaft is rotating at 500 rpm,
then the TCM can determine that the gear ratio is
2:1. In direct drive (3rd gear), the gear ratio changes
to 1:1. The gear ratio changes as clutches are applied
and released. By monitoring the length of time it
takes for the gear ratio to change following a shift
request, the TCM can determine the volume of fluid
used to apply or release a friction element.
The volume of transmission fluid needed to apply
the friction elements are continuously updated for
adaptive controls. As friction material wears, the vol-
ume of fluid need to apply the element increases.
Certain mechanical problems within the input
clutch assembly (broken return springs, out of posi-
tion snap rings, excessive clutch pack clearance,
improper assembly, etc.) can cause inadequate or out-
of-range element volumes. Also, defective Input/Out-
put Speed Sensors and wiring can cause these
conditions. The following chart identifies the appro-
priate clutch volumes and when they are monitored/
updated:
Fig. 14 Example of CVI Calculation
1 - OUTPUT SPEED SENSOR
2 - OUTPUT SHAFT
3 - CLUTCH PACK
4 - SEPARATOR PLATE
5 - FRICTION DISCS
6 - INPUT SHAFT
7 - INPUT SPEED SENSOR
8 - PISTON AND SEAL
TJ
ELECTRONIC CONTROL MODULES
8E - 15
TRANSMISSION CONTROL MODULE (Continued)
CLUTCH VOLUMES
Clutch
When Updated
Proper Clutch
Volume
Shift Sequence
Oil Temperature
Throttle Angle
L/R
2-1 or 3-1 coast
downshift
> 70°
< 5°
35 to 83
2/4
1-2 shift
> 110°
5 - 54°
20 to 77
OD
2-3 shift
48 to 150
UD
4-3 or 4-2 shift
> 5°
24 to 70
SHIFT SCHEDULES
As mentioned earlier, the TCM has programming
that allows it to select a variety of shift schedules.
Shift schedule selection is dependent on the follow-
ing:
• Shift lever position
• Throttle position
• Engine load
• Fluid temperature
• Software level
As driving conditions change, the TCM appropri-
ately adjusts the shift schedule. Refer to the follow-
ing table 42RLE Shift Schedule to determine the
appropriate operation expected, depending on driving
conditions.
42RLE SHIFT SCHEDULE
Schedule
Condition
Expected Operation
Extreme Cold
Oil temperature at start-up below
-16° F
Park, Reverse, Neutral and 2nd
gear only (prevents shifting which
may fail a clutch with frequent
shifts)
Cold
Oil temperature at start-up above
-12° F and below 36° F
– Delayed 2-3 upshift
(approximately 22-31 mph)
– Delayed 3-4 upshift (45-53 mph)
– Early 4-3 costdown shift
(approximately 30 mph)
– Early 3-2 coastdown shift
(approximately 17 mph)
– High speed 4-2, 3-2, 2-1 kickdown
shifts are prevented
– No EMCC
Warm
Oil temperature at start-up above
36° F and below 80 degree F
– Normal operation (upshift,
kickdowns, and coastdowns)
– No EMCC
Hot
Oil temperature at start-up above
80° F
– Normal operation (upshift,
kickdowns, and coastdowns)
– Full EMCC, no PEMCC except to
engage FEMCC (except at closed
throttle at speeds above 70-83 mph)
Overheat
Oil temperature above 240° F or
engine coolant temperature above
244° F
– Delayed 2-3 upshift (25-32 mph)
– Delayed 3-4 upshift (41-48 mph)
– 3rd gear FEMCC from 30-48 mph
– 3rd gear PEMCC from 27-31 mph
8E - 16
ELECTRONIC CONTROL MODULES
TJ
TRANSMISSION CONTROL MODULE (Continued)
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