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Jeep Grand Cherokee WK. Manual - part 354

STEP

RESISTANCE RANGE

REQUIRED INTERPRETATION

63<111<140.4

Fault Condition (short)

309.7<337<364.39

NEUTRAL from 4LO(1)

380.93< 414<448.20

NEUTRAL from 4HI(1)

910.87< 990< 1071.72

4LO

2024.17< 2200< 2381.61

4HI

Greater Than 8661.5<9000<9343

Fault condition (open)

NOTE: There is no requirement for the FDCM to distinguish between a neutral request from the 4LO or the
4HI position. Resistances in these ranges will be represented as a Neutral Switch Activation.

TRANSFER CASE MODE SENSOR SIGNAL

The Transfer Case Mode Sensor Signal Input will provide the FDCM feedback about the position of the transfer
case. The mode sensor will be a linear analog position sensor with a 1.4K +/- 20% potentiometer and a 1 K +/- 20%
wiper resistor that converts the motor shaft position into a multiplexed voltage.

FRONT AND REAR DIFFERENTIAL TEMPERATURE SENSORS

The Front and Rear Differential Temperature Sensors will provide a Temperature signal to the FDCM. The temper-
ature sensor will be of a resistive nature and supplied by the Drivetrain Sensor Supply.

TEMPERATURE

RESISTANCE k

Degrees C

Degrees F

Minimum

Maximum

-60

-76

1353.41

1838.59

-40

291.49

381.71

-30

-22

155.2

199.6

-20

-4

85.85

108.39

-10

49.25

61.43

29.33

35.99

17.99

21.81

11.37

13.61

9.12

10.88

7.37

8.75

104

4.9

5.75

122

3.33

3.88

140

2.31

2.67

158

1.63

1.87

176

1.17

1.34

194

0.86

0.97

100

212

0.64

0.72

110

230

0.48

0.54

120

248

0.37

0.41

130

266

0.28

0.32

140

284

0.21

0.25

150

302

0.17

0.20

NEUTRAL LAMP

There will be a LED indicator in the Shifter bezel to indicate to the driver that the Transfer Case is in the Neutral
gear. FDCM will be capable of driving the LED continuously at 25 mA.

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ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

FRONT AND REAR ELECTRONIC LIMITED SLIP DIFFERENTIAL PRESSURE SOLENOID

These outputs will control a Solenoid that regulates the oil pressure inside the Front and Rear Electrical Differential.
The oil pressure controls a clutch pack in the front differential that varies the torque transfer across the front or rear
axle.. The solenoid will be PWM controlled at a 1Khz frequency and with a 0 to 100% duty cycle capability.

TRANSFER CASE BI-DIRECTIONAL MOTOR CONTROL (A & B)

This output will control a Bi-directional DC motor that controls a clutch pack in the Transfer Case that varies the
torque transfer between the front and rear axles.

MODES OF OPERATION

Normal Operation

This mode is achieved by the ignition being switched in the RUN position, which powers up the 5V regulator and
generates the appropriate RESET for the microprocessor. This mode also includes any required power-up system
checks.

Shut Down Mode

This mode is activated when the ignition switch turned to the off position. The FDCM will perform any required Shut
Down tasks prior to turning off the 5V regulator.

Limp-In Mode

This mode is entered when the FDCM has detected an error condition that prevents the system from performing its’
required task. The FDCM operation will vary depending from modified operation to total system shut down based on
the failure that has occurred.

REMOVAL

1. Disconnect and isolate the battery negative cable.

2. Lift up rear seat to expose the park assist module

and final drive control module.

ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

8E - 263

3. Disconnect the module electrical connector (1).

4. Using a trim stick (special tool #C-4755) or equiv-

alent, gently pry back on the retaining tabs on the
mounting plate (2) and remove module.

INSTALLATION

1. Place the park assist module (3) in its location on

the mounting plate (2) and firmly snap into place.

2. Connect the electrical connector (1).

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ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

3. Lower the rear seat back down into position.

4. Connect the battery negative cable.

MODULE-FRONT CONTROL

DESCRIPTION

CAUTION: Do not exchange the Front Control
Module with the module from another vehicle. Mul-
tiple

vehicle

module

configurations

may

altered. Use only approved service parts when
replacing the module or exchanging the module
for diagnostic purposes.

The Front Control Module (FCM) (3) is a micro con-
troller based module located in the left front corner of
the engine compartment. The FCM mates directly to
the Integrated Power Module (IPM)(2). The IPM con-
nects directly to the battery and provides the primary
means of circuit protection and power distribution for
many of the vehicle electrical systems. The FCM con-
trols power to some of these vehicle systems electrical
and electromechanical loads based on inputs received
from hard wired switch inputs and data received on
the Controller Area Network (CAN) data bus circuit.

OPERATION

As messages are sent over the Controller Area Network (CAN) bus circuit, the Front Control Module (FCM) reads
these messages and controls power to some of the vehicles electrical systems by completing the circuit to ground
(low side driver) or completing the circuit to 12 volt power (high side driver). The following functions are controlled
by the FCM:

•

Front turn signals

•

Turn signal and tail lamps

•

Front and rear hazard warning lamps

•

Headlamps

•

Fog Lamps

•

Daytime running lamps - if equipped

•

Horn

ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

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