Jeep Liberty KJ. Manual — part 1487
•
supplies a reference voltage for the Throttle Position Sensor (TPS).
Secondary 5 volt supply:
•
supplies the required 5 volt power source to the oil pressure sensor.
•
supplies the required 5 volt power source for the Vehicle Speed Sensor (VSS) (if equipped).
•
supplies the 5 volt power source to the transmission pressure sensor (certain automatic transmissions).
IGNITION CIRCUIT SENSE
The ignition circuit sense input tells the PCM the ignition switch has energized the ignition circuit.
Battery voltage is also supplied to the PCM through the ignition switch when the ignition is in the RUN or START
position. This is referred to as the
9
ignition sense
9
circuit and is used to
9
wake up
9
the PCM. Voltage on the ignition
input can be as low as 6 volts and the PCM will still function. Voltage is supplied to this circuit to power the PCM’s
8-volt regulator and to allow the PCM to perform fuel, ignition and emissions control functions.
REMOVAL
Use the scan tool to reprogram the new powertrain control module (PCM) with the vehicles original identi-
fication number (VIN) and the vehicles original mileage. If this step is not done, a diagnostic trouble code
(DTC) may be set.
The PCM (1) is located in the engine compartment
near the battery.
To avoid possible voltage spike damage to the PCM,
ignition key must be off, and negative battery cable
must be disconnected before unplugging PCM con-
nectors.
1. Disconnect negative battery cable at battery.
2. Remove cover over electrical connectors. Cover
snaps onto PCM.
3. NGC Modules : Carefully unplug the four 38-way
connectors from PCM. JTEC Modules : Carefully
unplug the three 32–way connectors from PCM.
4. Remove three PCM mounting bolts (2) and remove
PCM from vehicle.
INSTALLATION
Use the scan tool to reprogram the new powertrain control module (PCM) with the vehicles original identi-
fication number (VIN) and the vehicles original mileage. If this step is not done, a diagnostic trouble code
(DTC) may be set.
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ELECTRONIC CONTROL MODULES
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1. Install PCM (1) and three mounting bolts (2) to
vehicle.
2. Tighten bolts. Refer to torque specifications.
3. Check pin connectors in the PCM and its connec-
tors for corrosion or damage. Also, the pin heights
in connectors should all be same. Repair as nec-
essary before installing connectors.
4. NGC Modules : Carefully install the four 38-way
connectors into PCM. JTEC Modules : Carefully
install the three 32–way connectors into PCM.
5. Install cover over electrical connectors. Cover
snaps onto PCM.
6. Install battery cable.
7. Use the scan tool to reprogram new PCM with
vehicles original Identification Number (VIN) and
original vehicle mileage.
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MODULE-TRANSMISSION CONTRO
DESCRIPTION
TRANSMISSION CONTROL MODULE - GASOLINE ENGINES
The Transmission Control Module (TCM) is a sub-
module within the Powertrain Control Module (PCM).
The PCM is located on the left inner fender.
TRANSMISSION CONTROL MODULE - DIESEL ENGINE
The Transmission Control Module (TCM) (3) is located
in the engine compartment on the left (driver) side and
is mounted to the dash panel.
OPERATION
TRANSMISSION CONTROL MODULE - GASOLINE ENGINES
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 transmis-
sion. Direct inputs are hard-wired to, and used specifically by the TCM. Indirect inputs originate from other compo-
nents/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
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•
CranKshaft Position sensor (CKP)
•
Transmission Range Sensor (TRS)
•
Pressure Switches (L/R, 2/4, OD)
•
Transmission Temperature Sensor (TTS) (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
•
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 (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 responsibilities and functions:
•
Storing and maintaining Clutch Volume Indices (CVI)
•
Storing and selecting appropriate Shift Schedules
•
System self-diagnostics
•
Diagnostic capabilities (with scan tool)
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)
CLUTCH VOLUME INDEX (CVI)
An important function of the TCM is to monitor Clutch Volume Index (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.
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