Jeep Grand Cherokee WK. Manual — part 360
Shift Time Adaptation (Shift Overlap Adaptation, Working Pressure)
Shift time adaptation is the ability of the TCM to electronically alter the time it takes to go from one gear to another.
Shift time is defined as the time it takes to disengage one shift member while another is being applied. Shift time
adaptation is divided into four categories:
1. Accelerating upshift, which is an upshift under a load. For shift time adaptation for the 1-2 upshift to take
place, the transmission must shift from 1st to 2nd in six different engine load ranges vs. transmission output
speed ranges.
2. Decelerating upshift, which is an upshift under no load. This shift is a rolling upshift and is accomplished by
letting the vehicle roll into the next gear.
3. Accelerating downshift, which is a downshift under load. This shift can be initiated by the throttle, with or with-
out kickdown. The shift selector can also be used.
4. Decelerating downshift, which is accomplished by coasting down. As the speed of the vehicle decreases, the
transmission downshifts.
Fill Pressure Adaptation (Apply Pressure Adaptation, Modulating Pressure)
Fill pressure adaptation is the ability of the TCM to modify the pressure used to engage a shift member. The value
of this pressure determines how firm the shift will be.
•
If too much pressure is used, the shift will be hard.
•
If too little pressure is used, the transmission may slip.
The pressure adjustment is needed to compensate for the tolerances of the shift pressure solenoid valve. The
amount the solenoid valve opens as well as how quickly the valve can move, has an effect on the pressure. The
return spring for the shift member provides a resistance that must be overcome by the pressure in order for shift
member to apply. These return springs have slightly different values. This also affects the application pressure and
is compensated for by fill pressure adaptation.
Fill Time Adaptation (Engagement Time Adaptation)
Fill time is the time it takes to fill the piston cavity and take up any clearances for a friction element (clutch or
brake). Fill time adaptation is the ability of the TCM to modify the time it takes to fill the shift member by applying
a preload pressure.
CONTROLLER MODES OF OPERATION
Permanent Limp-In Mode
When the TCM determines there is a non-recoverable condition present that does not allow proper transmission
operation, it places the transmission in permanent Limp-In Mode. When the condition occurs the TCM turns off all
solenoids as well as the solenoid supply output circuit. If this occurs while the vehicle is moving, the transmission
remains in the current gear position until the ignition is turned off or the shifter is placed in the
9
P
9
position. When
the shifter has been placed in
9
P,
9
the transmission only allows 2nd gear operation. If this occurs while the vehicle
is not moving, the transmission only allows operation in 2nd gear.
Temporary Limp-In Mode
This mode is the same as the permanent Limp-In Mode except if the condition is no longer present, the system
resumes normal operation.
Under Voltage Limp-In Mode
When the TCM detects that system voltage has dropped below 8.5 volts, it disables voltage-dependant diagnostics
and places the transmission in the temporary Limp-In Mode. When the TCM senses that the voltage has risen
above 9.0 volts, normal transmission operation is resumed.
Hardware Error Mode
When the TCM detects a major internal error, the transmission is placed in the permanent Limp-In Mode and
ceases all communication over the CAN bus. When the TCM has entered this mode normal transmission operation
does not resume until all DTCs are cleared from the TCM.
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Loss of Drive
If the TCM detects a situation that has resulted or may result in a catastrophic engine or transmission problem, the
transmission is placed in the neutral position. Improper Ratio, Input Sensor Overspeed or Engine Overspeed DTCs
cause the loss of drive.
Controlled Limp-in Mode
When a failure does not require the TCM to shut down the solenoid supply, but the failure is severe enough that the
TCM places the transmission into a predefined gear, there are several shift performance concerns. For instance, if
the transmission is slipping, the controller tries to place the transmission into 3rd gear and maintain 3rd gear for all
forward drive conditions.
4.7L/5.7L VEHICLES
The Transmission Control Module (TCM) controls 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 hardwired to, and used specifically by the TCM. Indirect inputs originate from other
components/modules, and are shared with the TCM via the vehicle communication 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
•
Transmission Range Sensor
•
Pressure Switches
•
Transmission Temperature Sensor
•
Input Shaft Speed Sensor
•
Output Shaft Speed Sensor
•
Line Pressure Sensor
Some examples of indirect inputs to the TCM are:
•
Engine/Body Identification
•
Manifold Pressure
•
Target Idle
•
Torque Reduction Confirmation
•
Engine Coolant Temperature
•
Ambient/Battery Temperature
•
Scan Tool Communication
Based on the information received from these various 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
•
Torque Reduction Request
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 responsibilities and functions:
•
Storing and maintaining Clutch Volume Indexes (CVI)
•
Storing and selecting appropriate Shift Schedules
•
System self-diagnostics
•
Diagnostic capabilities (with scan tool)
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NOTE: If the TCM has been replaced, the “Quick Learn Procedure” must be performed. (Refer to 8 - ELEC-
TRICAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE - STANDARD PROCE-
DURE)
BATTERY FEED
A fused, direct battery feed to the TCM is used for continuous power. This battery voltage is necessary to retain
adaptive learn values in the TCM’s RAM (Random Access Memory). When the battery (B+) is disconnected, this
memory is lost. When the battery (B+) is restored, this memory loss is detected by the TCM and a Diagnostic Trou-
ble Code (DTC) is set.
CLUTCH VOLUME INDEXES (CVI)
An important function of the TCM is to monitor Clutch Volume Indexes (CVI). CVIs represent the volume of fluid
needed to compress a clutch pack.
The TCM monitors gear ratio changes by monitoring 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 Output Speed Sensor
provides the TCM with output shaft speed information.
By comparing the two inputs, the TCM can determine transmission gear position. This is important to the CVI cal-
culation because the TCM determines CVIs by monitoring how long it takes for a gear change to occur.
Gear ratios can be determined by using the DRBIII
T
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.
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 volume of fluid
need to apply the element increases.
Certain mechanical failures within the input clutch
assembly can cause inadequate or out-of-range ele-
ment volumes. Also, defective Input/Output Speed
Sensors and wiring can cause these conditions. The
following chart identifies the appropriate clutch vol-
umes and when they are monitored/updated:
CLUTCH VOLUMES
Clutch
When Updated
Proper Clutch Volume
L/R
2-1 or 3-1 downshift
45 to 134
2C
3-2 kickdown shift
25 to 85
OD
2-3 upshift
30 to 100
4C
3-4 upshift
30 to 85
UD
4-3 kickdown shift
25 to 100
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 following:
•
Shift lever position
•
Throttle position
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•
Engine load
•
Fluid temperature
•
Software level
As driving conditions change, the TCM appropriately adjusts the shift schedule. Refer to the following chart to deter-
mine the appropriate operation expected, depending on driving conditions.
Schedule
Condition
Expected Operation
Extreme Cold
Oil temperature below -16° F
-Park, Reverse, Neutral and 1st and
3rd gear only in D position, 2nd
gear only in Manual 2 or L
-No EMCC
Super Cold
Oil temperature between -12° F and
10° F
- Delayed 2-3 upshift
- Delayed 3-4 upshift
- Early 4-3 coastdown shift
- High speed 4-2, 3-2, 2-1 kickdown
shifts are prevented
-Shifts at high throttle openings willl
be early.
- No EMCC
Cold
Oil temperature between 10° F and
36° F
-Shift schedule is the same as
Super Cold except that the 2-3
upshifts are not delayed.
Warm
Oil temperature between 40° F and
80° F
- Normal operation (upshift,
kickdowns, and coastdowns)
- No EMCC
Oil temperature between 80° F and
240° F
- Normal operation (upshift,
kickdowns, and coastdowns)
Hot
- Normal EMCC operation
Overheat
Oil temperature above 240° F or
engine coolant temperature above
244° F
- Delayed 2-3 upshift
- Delayed 3-4 upshift
- 3rd gear FEMCC from 30-48 mph
- 3rd gear PEMCC above 35 mph
- Above 25 mph the torque
converter will not unlock unless the
throttle is closed or if a wide open
throttle 2nd PEMCC to 1 kickdown
is made
STANDARD PROCEDURE
ADAPTATION - 3.7L VEHICLES
The adaptation procedure requires the use of the appropriate scan tool. This program allows the electronic trans-
mission system to re-calibrate itself. This will provide the proper baseline transmission operation. The adaptation
procedure should be performed if any of the following procedures are performed:
•
Transmission Assembly Replacement
•
Transmission Control Module Replacement
•
Clutch Plate and/or Seal Replacement
•
Electrohydraulic Unit Replacement or Recondition
1. With the scan tool, reset the Transmission adaptives. Resetting the adaptives will set the adaptives to factory
settings.
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