sensor DODGE RAM 1500 1998 2.G Repair Manual

HEATED SEAT MODULE
DESCRIPTION
The heated seat module is also known as the Seat
Heat Interface Module. The heated seat module (Fig.
3) is located under the drivers front seat cushion,
where it is secured to a mounting bracket. The
heated seat module has a single connector receptacle
that allows the module to be connected to all of the
required inputs and outputs through the seat wire
harness.
The heated seat module is an electronic micropro-
cessor controlled device designed and programmed to
use inputs from the battery, the two heated seat
switches and the two heated seat sensors to operate
and control the heated seat elements in both front
seats and the two heated seat indicator lamp Light-
Emitting Diodes (LEDs) in each heated seat switch.
The heated seat module is also programmed to per-
form self-diagnosis of certain heated seat system
functions and provide feedback of that diagnosis
through the heated seat switch indicator lamps.
The heated seat module cannot be repaired. If the
heated seat module is damaged or faulty, the entire
module must be replaced.
OPERATION
The heated seat module operates on fused battery
current received from the integrated power module.
Inputs to the module include a resistor multiplexed
heated seat switch request circuit for each of the two
heated seat switches and the heated seat sensor
inputs from the seat cushions of each front seat. In
response to those inputs the heated seat module con-
trols battery current feeds to the heated seat ele-ments and sensors, and controls the ground for the
heated seat switch indicator lamps.
When a heated seat switch (Driver or Passenger) is
depressed a signal is received by the heated seat
module, the module energizes the proper indicator
LED (Low or High) in the switch by grounding the
indicator lamp circuit to indicate that the heated seat
system is operating. At the same time, the heated
seat module energizes the selected heated seat sensor
circuit and the sensor provides the module with an
input indicating the surface temperature of the
selected seat cushion.
The Low heat set point is about 36É C (96.8É F),
and the High heat set point is about 42É C (107.6É F).
If the seat cushion surface temperature input is
below the temperature set point for the selected tem-
perature setting, the heated seat module energizes
an N-channel Field Effect Transistor (N-FET) within
the module which energizes the heated seat elements
in the selected seat cushion and back. When the sen-
sor input to the module indicates the correct temper-
ature set point has been achieved, the module
de-energizes the N-FET which de-energizes the
heated seat elements. The heated seat module will
continue to cycle the N-FET as needed to maintain
the selected temperature set point.
If the heated seat module detects a heated seat
sensor value input that is out of range or a shorted
or open heated seat element circuit, it will notify the
vehicle operator or the repair technician of this con-
dition by flashing the High and/or Low indicator
lamps in the affected heated seat switch. Refer to
Diagnosis and Testing Heated Seat Systemin
Heated Systems for flashing LED diagnosis and test-
ing procedures. Refer toDiagnosis and Testing
Heated Seat Modulein this section for heated seat
module diagnosis and testing procedures.
DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
If a heated seat fails to heat and one or both of the
indicator lamps on a heated seat switch flash, refer
toDiagnosis and Testing Heated Seat Systemin
Heated Seats for the location of flashing LED heated
seat system diagnosis and testing procedures. If a
heated seat heats but one or both indicator lamps on
the heated seat switch fail to operate, test the heated
seat switch. Refer toDiagnosis and Testing
Heated Seat Switchin Heated Seats for heated
seat switch diagnosis and testing procedures. If the
heated seat switch checks OK, proceed as follows.
(1) Check the heated seat element (Refer to 8 -
ELECTRICAL/HEATED SEATS/HEATED SEAT
ELEMENT - DIAGNOSIS AND TESTING).
Fig. 3 Heated Seat Module
1 - MOUNTING TABS (NOT USED ON DR)
2 - HEATED SEAT MODULE
3 - ELECTRICAL CONNECTOR RECEPTACLE
8E - 6 ELECTRONIC CONTROL MODULESDR

(2) Check the heated seat sensor (Refer to 8 -
ELECTRICAL/HEATED SEATS/HEATED SEAT
SENSOR - DIAGNOSIS AND TESTING).
(3) Check the heated seat switch (Refer to 8 -
ELECTRICAL/HEATED SEATS/DRIVER HEATED
SEAT SWITCH - DIAGNOSIS AND TESTING).
NOTE: Refer to Wiring for the location of complete
heated seat system wiring diagrams and connector
pin-out information.
(4) Using a voltmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for voltage at the appropriate pin cavities. 12v
should be present. If OK go to Step 5, if Not, Repair
the open or shorted voltage supply circuit as
required.
(5) Using a ohmmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for proper continuity to ground on the ground
pin cavities. Continuity should be present. If OK
replace the heated seat module with a known good
unit and retest system, if Not OK, Repair the open or
shorted ground circuit as required.
REMOVAL
(1) Position the driver seat to the full rearward
and inclined position.
(2) Working under the driver front seat, remove
the two heated seat module retaining screws. Due to
the fact that the retaining screws are installed with
the seat cushion pan removed, a small right angle
screwdriver will be required to access and remove the
screws.
(3) Disconnect the seat wire harness connector
from the connector receptacle on the back of the
heated seat module. Depress the connector retaining
tab and pull straight apart.
(4) Remove the heated seat module from under the
front seat.
INSTALLATION
(1) Position the heated seat module under the
front seat.
(2) Connect the seat wire harness connector on the
connector receptacle on the back of the heated seat
module.
(3) Working under the driver front seat, install the
heated seat module retaining screws.
(4) Re-position the driver seat.
POWERTRAIN CONTROL
MODULE
DESCRIPTION
DESCRIPTION - PCM
The Powertrain Control Module (PCM) is located
in the right-rear section of the engine compartment
under the cowl (Fig. 4).
Two different PCM's are used (JTEC and
NGC). These can be easily identified. JTEC's
use three 32±way connectors, NGC's use four
38±way connectors
DESCRIPTION - MODES OF OPERATION
As input signals to the Powertrain Control Module
(PCM) change, the PCM adjusts its response to the
output devices. For example, the PCM must calculate
different injector pulse width and ignition timing for
idle than it does for wide open throttle (WOT).
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input
signals and responds only according to preset PCM
programming. Input from the oxygen (O2S) sensors
is not monitored during Open Loop modes.
Fig. 4 POWERTRAIN CONTROL MODULE (PCM)
LOCATION
1 - COWL GRILL
2 - PCM
3 - COWL (RIGHT-REAR)
DRELECTRONIC CONTROL MODULES 8E - 7
HEATED SEAT MODULE (Continued)

During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.
The fuel injection system has the following modes
of operation:
²Ignition switch ON
²Engine start-up (crank)
²Engine warm-up
²Idle
²Cruise
²Acceleration
²Deceleration
²Wide open throttle (WOT)
²Ignition switch OFF
The ignition switch On, engine start-up (crank),
engine warm-up, acceleration, deceleration and wide
open throttle modes are Open Loop modes. The idle
and cruise modes, (with the engine at operating tem-
perature) are Closed Loop modes.
IGNITION SWITCH (KEY-ON) MODE
This is an Open Loop mode. When the fuel system
is activated by the ignition switch, the following
actions occur:
²The PCM pre-positions the idle air control (IAC)
motor.
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the engine coolant tempera-
ture sensor input. The PCM modifies fuel strategy
based on this input.
²Intake manifold air temperature sensor input is
monitored.
²Throttle position sensor (TPS) is monitored.
²The auto shutdown (ASD) relay is energized by
the PCM for approximately three seconds.
²The fuel pump is energized through the fuel
pump relay by the PCM. The fuel pump will operate
for approximately three seconds unless the engine is
operating or the starter motor is engaged.
²The O2S sensor heater element is energized via
the ASD or O2S heater relay. The O2S sensor input
is not used by the PCM to calibrate air-fuel ratio dur-
ing this mode of operation.
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The PCM receives inputs from:²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the
engine, it will shut down the fuel injection system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
The PCM determines the proper ignition timing
according to input received from the crankshaft posi-
tion sensor.
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-
up, the PCM receives inputs from:
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
Based on these inputs the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
²The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim-
ing.
²The PCM operates the A/C compressor clutch
through the A/C compressor clutch relay. This is done
if A/C has been selected by the vehicle operator and
specified pressures are met at the high and low±pres-
sure A/C switches. Refer to Heating and Air Condi-
tioning for additional information.
²When engine has reached operating tempera-
ture, the PCM will begin monitoring O2S sensor
input. The system will then leave the warm-up mode
and go into closed loop operation.
8E - 8 ELECTRONIC CONTROL MODULESDR
POWERTRAIN CONTROL MODULE (Continued)

IDLE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At idle speed, the PCM
receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Battery voltage
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen sensors
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
injection sequence and injector pulse width by turn-
ing the ground circuit to each individual injector on
and off.
²The PCM monitors the O2S sensor input and
adjusts air-fuel ratio by varying injector pulse width.
It also adjusts engine idle speed through the idle air
control (IAC) motor.
²The PCM adjusts ignition timing by increasing
and decreasing spark advance.
²The PCM operates the A/C compressor clutch
through the A/C compressor clutch relay. This is done
if A/C has been selected by the vehicle operator and
specified pressures are met at the high and low±pres-
sure A/C switches. Refer to Heating and Air Condi-
tioning for additional information.
CRUISE MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At cruising speed, the PCM
receives inputs from:
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)²Oxygen (O2S) sensors
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then adjust
the injector pulse width by turning the ground circuit
to each individual injector on and off.
²The PCM monitors the O2S sensor input and
adjusts air-fuel ratio. It also adjusts engine idle
speed through the idle air control (IAC) motor.
²The PCM adjusts ignition timing by turning the
ground path to the coil(s) on and off.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
ACCELERATION MODE
This is an Open Loop mode. The PCM recognizes
an abrupt increase in throttle position or MAP pres-
sure as a demand for increased engine output and
vehicle acceleration. The PCM increases injector
pulse width in response to increased throttle opening.
DECELERATION MODE
When the engine is at operating temperature, this
is an Open Loop mode. During hard deceleration, the
PCM receives the following inputs.
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Vehicle speed
If the vehicle is under hard deceleration with the
proper rpm and closed throttle conditions, the PCM
will ignore the oxygen sensor input signal. The PCM
will enter a fuel cut-off strategy in which it will not
supply a ground to the injectors. If a hard decelera-
tion does not exist, the PCM will determine the
proper injector pulse width and continue injection.
Based on the above inputs, the PCM will adjust
engine idle speed through the idle air control (IAC)
motor.
The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
DRELECTRONIC CONTROL MODULES 8E - 9
POWERTRAIN CONTROL MODULE (Continued)

WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the PCM receives the following
inputs.
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
During wide open throttle conditions, the following
occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off. The PCM ignores the oxygen sensor input
signal and provides a predetermined amount of addi-
tional fuel. This is done by adjusting injector pulse
width.
²The PCM adjusts ignition timing by turning the
ground path to the coil(s) on and off.
IGNITION SWITCH OFF MODE
When ignition switch is turned to OFF position,
the PCM stops operating the injectors, ignition coil,
ASD relay and fuel pump relay.
DESCRIPTION - 5 VOLT SUPPLIES
Two different Powertrain Control Module (PCM)
five volt supply circuits are used; primary and sec-
ondary.
DESCRIPTION - IGNITION CIRCUIT SENSE
This circuit ties the ignition switch to the Power-
train Control Module (PCM).
DESCRIPTION - POWER GROUNDS
The Powertrain Control Module (PCM) has 2 main
grounds. Both of these grounds are referred to as
power grounds. All of the high-current, noisy, electri-
cal devices are connected to these grounds as well as
all of the sensor returns. The sensor return comes
into the sensor return circuit, passes through noise
suppression, and is then connected to the power
ground.
The power ground is used to control ground cir-
cuits for the following PCM loads:
²Generator field winding
²Fuel injectors
²Ignition coil(s)
²Certain relays/solenoids
²Certain sensors
DESCRIPTION - SENSOR RETURN
The Sensor Return circuits are internal to the Pow-
ertrain Control Module (PCM).
Sensor Return provides a low±noise ground refer-
ence for all engine control system sensors. Refer to
Power Grounds for more information.
OPERATION
OPERATION - PCM
The PCM operates the fuel system. The PCM is a
pre-programmed, triple microprocessor digital com-
puter. It regulates ignition timing, air-fuel ratio,
emission control devices, charging system, certain
transmission features, speed control, air conditioning
compressor clutch engagement and idle speed. The
PCM can adapt its programming to meet changing
operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as Powertrain Control Module
(PCM) Outputs. The sensors and switches that pro-
vide inputs to the PCM are considered Powertrain
Control Module (PCM) Inputs.
The PCM adjusts ignition timing based upon
inputs it receives from sensors that react to: engine
rpm, manifold absolute pressure, engine coolant tem-
perature, throttle position, transmission gear selec-
tion (automatic transmission), vehicle speed, power
steering pump pressure, and the brake switch.
The PCM adjusts idle speed based on inputs it
receives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, engine
coolant temperature and from inputs it receives from
the air conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
NOTE: PCM Inputs:
²ABS module (if equipped)
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²A/C pressure transducer
²Auto shutdown (ASD) sense
²Battery temperature sensor
²Battery voltage
²Brake switch
²J1850 bus (+) circuits
²J1850 bus (-) circuits
²Camshaft position sensor signal
²Crankshaft position sensor
8E - 10 ELECTRONIC CONTROL MODULESDR
POWERTRAIN CONTROL MODULE (Continued)

²Data link connection for DRB scan tool
²EATX module (if equipped)
²Engine coolant temperature sensor
²Fuel level (through J1850 circuitry)
²Generator (battery voltage) output
²Ignition circuit sense (ignition switch in on/off/
crank/run position)
²Intake manifold air temperature sensor
²Knock sensors (2 on 3.7L engine)
²Leak detection pump (switch) sense (if equipped)
²Manifold absolute pressure (MAP) sensor
²Oil pressure
²Oxygen sensors
²Park/neutral switch (auto. trans. only)
²Power ground
²Power steering pressure switch (if equipped)
²Sensor return
²Signal ground
²Speed control multiplexed single wire input
²Throttle position sensor
²Transfer case switch (4WD range position)
²Vehicle speed signal
NOTE: PCM Outputs:
²A/C clutch relay
²Auto shutdown (ASD) relay
²J1850 bus (+/-) circuits for: speedometer, voltme-
ter, fuel gauge, oil pressure gauge/lamp, engine temp.
gauge and speed control warn. lamp
²Data link connection for DRB scan tool
²EGR valve control solenoid (if equipped)
²EVAP canister purge solenoid
²Five volt sensor supply (primary)
²Five volt sensor supply (secondary)
²Fuel injectors
²Fuel pump relay
²Generator field driver (-)
²Generator field driver (+)
²Idle air control (IAC) motor
²Ignition coil(s)
²Leak detection pump (if equipped)
²Malfunction indicator lamp (Check engine lamp).
Driven through J1850 circuits.²Oxygen sensor heater relays
²Oxygen sensors (pulse width modulated)
²Radiator cooling fan relay (pulse width modu-
lated)
²Speed control vacuum solenoid
²Speed control vent solenoid
²Tachometer (if equipped). Driven through J1850
circuits.
²Transmission convertor clutch circuit. Driven
through J1850 circuits.
OPERATION - 5 VOLT SUPPLIES
Primary 5±volt supply:
²supplies the required 5 volt power source to the
Crankshaft Position (CKP) sensor.
²supplies the required 5 volt power source to the
Camshaft Position (CMP) sensor.
²supplies a reference voltage for the Manifold
Absolute Pressure (MAP) sensor.
²supplies a reference voltage for the Throttle
Position Sensor (TPS) sensor.
Secondary 5±volt supply:
²supplies the required 5 volt power source to the
oil pressure sensor.
²supplies the required 5 volt power source for the
Vehicle Speed Sensor (VSS) (if equipped).
²supplies the 5 volt power source to the transmis-
sion pressure sensor (certain automatic transmis-
sions).
OPERATION - 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
the9ignition sense9circuit and is used to9wake up9
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 reg-
ulator and to allow the PCM to perform fuel, ignition
and emissions control functions.
DRELECTRONIC CONTROL MODULES 8E - 11
POWERTRAIN CONTROL MODULE (Continued)

TRANSFER CASE CONTROL
MODULE
DESCRIPTION
The Transfer Case Control Module (TCCM) (Fig. 8)
is a microprocessor-based assembly, controlling the
4X4 transfer case shift functions via the actuation of
a shift motor and utilizing the feedback of a mode
sensor assembly. Communication is via the PCI serial
bus. Inputs include user selectable 4X4 modes that
include 2WD, AWD, 4HI, 4LO, and Neutral. The logic
and driver circuitry is contained in a molded plastic
housing with an embedded heat-sink and is located
behind the left side of the lower instrument panel.
OPERATION
The Transfer Case Control Module (TCCM) utilizes
the input from the transfer case mounted mode sen-
sor, the instrument panel mounted selector switch,
and the following information from the vehicle's PCI
serial bus to determine if a shift is allowed.
²Engine RPM and Vehicle Speed
²Diagnostic Requests
²Manual Transmission and Brake Applied
²PRNDL
²Ignition Status
²ABS Messages
Once the TCCM determines that a requested shift
is allowed, it actuates the bi-directional shift motor
as necessary to achieve the desired transfer case
operating mode. The TCCM also monitors the mode
sensor while controlling the shift motor to determine
the status of the shift attempt.Several items can cause the requested shift not to
be completed. If the TCCM has recognized a fault
(DTC) of some variety, it will begin operation in one
of four Functionality Levels. These levels are:
²Level Zero- Normal Operation.
²Level One- Only Mode Shifts Are Allowed.
²Level Two- Only Mode Shifts and Shifts Into
LOW Are Allowed (No Neutral Shifts Are Allowed).
²Level Three- No Shifts Are Allowed
The TCCM can also be operating in one of three
possible power modes. These power modes are:
²Full Power Modeis the normal operational
mode of the module. This mode is achieved by normal
PCI bus traffic being present and the ignition being
in the RUN position.
²Reduced Power Modewill be entered when
the ignition has been powered off. In this state, the
module will shut down power supplied to external
devices, and to electronic interface inputs and out-
puts. From this state the module can enter either
Sleep Mode or Full Power Mode. To enter this mode,
the module must receive an ignition message denot-
ing that the ignition is off, or not receive any mes-
sages for 5  0.5 seconds. To exit this mode, the
module must receive one ignition message that
denotes that the ignition is in the RUN position.
²Sleep Modewill be entered, from the Reduced
Power Mode, when no PCI traffic has been sensed for
20  1 seconds. If during Sleep Mode the module
detects PCI bus traffic, it will revert to the Reduced
Power mode while monitoring for ignition messages.
It will remain in this state as long as there is traffic
other than run or start messages, and will return to
Sleep mode if the bus goes without traffic for 20  1
seconds.
SHIFT REQUIREMENTS
If the TCCM is in full power mode and at function-
ality level zero, it uses the following criteria to deter-
mine if a shift is allowed.
If any of the driver controllable conditions are not
met once the shift request is recognized, the TCCM
will solidly illuminate the source position's LED and
flash the desired position's LED for all shifts except
NEUTRAL. The NEUTRAL shift LED strategy will
be discussed later.
Mode shiftswill be allowed regardless of trans-
mission gear or vehicle speed, whenever the following
conditions are met:
²Front and rear wheel speed are within 21 km/hr
(13 mph).
²A change in the Selector switch state indicates
that a mode shift has been requested.
²A valid mode sensor signal is being sensed by
the TCCM.
Fig. 8 Transfer Case Control Module (TCCM)
Location
1 - INSTRUMENT PANEL
2 - TRANSFER CASE CONTROL MODULE (TCCM)
3 - TRANSFER CASE SELECTOR SWITCH
8E - 16 ELECTRONIC CONTROL MODULESDR

²Proper transmit/receive messages are occurring
on the PCI bus.
²Ignition key switch is in the RUN position.
Range shiftswill be allowed only if all of the fol-
lowing conditions are met:
²Front and rear wheel speed are within 21 km/hr
(13 mph).
²A change in the Selector Switch state indicating
a range shift has been requested.
²Transmission in NEUTRAL signal must be rec-
ognized for at least 1.5 seconds  100 msec. (Auto-
matic transmissions only)
²Proper transmit/receive messages are occurring
on the PCI bus.
²Clutch signal is recognized for 500 msec   50
msec (Manual transmissions only).
²Vehicle speed is less than or equal to 4.8 km/hr
(3 miles per hour).
²Ignition key switch is in the RUN position.
²A valid mode sensor signal is being sensed by
the TCCM.
Ashift into transfer case Neutralwill be
allowed only if all of the following conditions are met:
²Front and rear wheel speed are within 21 km/hr
(13 mph).
²The recessed Neutral Selection switch has been
depressed continuously for 4.0 seconds  100 msec
while all shift conditions have been continuously met.
²Transmission in NEUTRAL signal recognized
from the bus. (Automatic transmissions only)
²Clutch signal is recognized from the bus (Man-
ual transmissions only).
²Proper message transmissions/receptions are
occurring on the PCI bus.
²Vehicle speed is less than or equal to 4.8 km/hr
(3 miles per hour).
²Ignition key switch is in the RUN position,
engine off.
²Foot Brake is applied.
²A valid mode sensor signal is being sensed by
the TCCM.
Ashift out of transfer case Neutralwill be
allowed only if all of the following conditions are met:
²Front and rear wheel speed are within 21 km/hr
(13 mph).
²The recessed Neutral Selection switch has been
depressed continuously for 1.0 seconds  100 msec
while all shift conditions have been continuously met.
²Transmission in NEUTRAL signal recognized
from the bus.(Automatic transmissions only)
²Clutch signal is recognized from the bus (Man-
ual transmissions only).
²Proper message transmissions/receptions are
occurring on the PCI bus.
²Vehicle speed is less than or equal to 4.8 km/hr
(3 miles per hour).²Ignition key switch is in the RUN position.
²Foot Brake is applied.
²A valid mode sensor signal is being sensed by
the TCCM.
SHIFT SEQUENCES
Once all the driver controllable conditions for the
requested shift have been met, the TCCM begins a
shift timer with a maximum duration of 1 second per
'D' channel transition. If the shift timer expires
before the TCCM recognizes to correct mode sensor
code, the shift is considered to have been blocked.
The blocked shift will increment the blocked shift
counter by one. The TCCM strategy for handling
blocked shifts will be described later. The process the
TCCM performs for the various shifts will be
described first.
RANGE AND MODE SHIFTS
The process for performing all the range and mode
shifts are the same. The following steps describe the
process.
²Allow time for Selector Switch debounce; 250
msec  50 msec.
²Extinguish the source gear's LED while flashing
desired transfer case position's LED.
²Engage the shift motor for a maximum of 1 sec-
ond  100 msec per 'D' channel transition in the des-
tination gear's direction while monitoring the mode
sensor channel transitions.
²Disengage the shift motor when the correct
mode sensor code is recognized.
²Solidly illuminate the selected gear's LED.
²Transmit a bus message that the transfer case
shift is complete.
²If the desired mode sensor code is not received
after the shift timer expires (ie. a blocked or other
condition exists), stop driving the motor and wait for
200 msec  50 msec. The shift motor is then reversed
in the direction back toward the source gear for up to
1.0 seconds  100 msec. per 'D' channel. The TCCM
waits for 2.0 seconds  50 msec. and repeats the
attempt to shift to the desired position.
The exception to the preceding sequence is when a
shift from 4L to 2WD/AWD is requested. If 2WD/
AWD is requested from the 4L position, the transfer
case is first driven to the 4H position. If the 4H posi-
tion is reached, the transfer case is then driven back
to the 2WD/AWD position and the shift is considered
complete. If the transfer case does not reach any the
4H position, but is in the 2WD/AWD 'D' channel, or
the 2WD/AWD between gear position on the 4H side
of 2WD/AWD, the shift is also considered complete.
DRELECTRONIC CONTROL MODULES 8E - 17
TRANSFER CASE CONTROL MODULE (Continued)

SHIFT OUT OF NEUTRAL
The following steps describe the process for a shift
out of NEUTRAL.
²Extinguish the Neutral LED.
²Engage the shift motor for a maximum of 1 sec-
ond  100 msec toward the transfer case 4H mode
position while monitoring the mode sensor channel
transitions.
²Disengage the shift motor when the correct
mode sensor code is recognized.
²Extinguish the Neutral LED.
²Transmit a bus message that the transfer case
shift is complete.
²If the desired mode sensor code is not received
after the shift timer expires (ie. a blocked or other
condition exists), stop driving the motor and wait for
200 msec  50 msec. The shift motor is then reversed
in the direction back toward the source gear for up to
1.0 seconds 100 msec. The TCCM waits for 2.0 sec-
onds  50 msec. and repeats the attempt to shift to
the desired position.
²When the Neutral button is released, if the 4H
position is the desired position, the shift is complete.
Illuminate the 4H LED.
²Otherwise when the Neutral button is released,
if all of the shift requirements are being met then
engage the shift motor towards the desired position
for 1 second  100 msec per 'D' channel. (if require-
ments for shifting are not met, illuminate the 4H
LED and flash the destination LED as an indication
to the driver that all of the driver controllable shift
conditions are not being met). If this requires
another range or mode shift, begin the range/mode
shift process.
²If the desired mode sensor code is not received
after the shift timer expires (i.e. a blocked or other
condition exists), refer to the section on Blocked Shift
Strategy.
BLOCKED SHIFT STRATEGY
When a shift is commanded, the shift motor will be
driven towards its destination position, except in the
case of shifting out of Neutral if 4L was selected (the
transfer case will shift to the 4H position first, before
proceeding to 4L). If the shift is blocked on the way
to the destination, the TCCM may attempt to drivethe motor back to the original position. This process
will be allowed to occur 5 times. If the transfer case
has reached a non-NEUTRAL 'D' channel during the
shift re-attempts, the LED for the achieved gear posi-
tion is illuminated and the shift attempts are
stopped. To re-attempt the desired shift, the selector
switch will need to be rotated to the current position
until the switch debounce timer expires then a shift
will need to be requested again.
At the end of the 5th blocked attempt, the shift
motor is driven towards the last known 'D' channel
position. If this motor drive allows the transfer case
to reach the 2WD/AWD 'D' channel, or the 2WD/AWD
between gear position on the 4H side of 2WD/AWD,
the shift is considered complete and the shift
attempts are ended.
If the mode sensor is in the NEUTRAL region at
the expiration of the shift timer, the TCCM will con-
tinue to make the shift attempts according to the
blocked shift strategy independent of whether or not
the driver controlled conditions are met.
For shifts from NEUTRAL, if all 5 attempts fail to
reach the desired position (which by default is 4H),
the motor will be driven to stall in the direction of
4H or 4L, depending on the achieved position. If the
transfer case has reached the 2WD/AWD or 4L
between gear position nearest the NEUTRAL posi-
tions and the shift conditions are no longer being
met, the transfer case will be driven toward the cor-
responding 'D' channel. Otherwise, the transfer case
will be driven in the direction opposite the last
attempt with the desired target being 4H or 4L.
If the transfer case reaches the 2WD/AWD 'D'
channel when being driven in the 4H direction, then
one final 1.0 second drive toward 4H is attempted. If
the transfer case then reaches any of the 4H posi-
tions, the shift is considered complete and the 4H
LED is illuminated. If the transfer case is still the
2WD/AWD position, the shift is considered complete
and the 2WD/AWD LED is illuminated.
NOTE: If after the 5th blocked shift and reversal
attempt, if the transfer case position is in the NEU-
TRAL region, shift attempts will continue until a
non-NEUTRAL 'D' channel is reached.
8E - 18 ELECTRONIC CONTROL MODULESDR
TRANSFER CASE CONTROL MODULE (Continued)

SHIFT REVERSAL TARGETS
If the shift timer expires (1 second per 'D' channel)
and the transfer case has not reached the desired
position, all shifts will attempt to return to their
original position with the exceptions of:
²If the intended shift is going to the High rail
from Low and can't make it, but it can make the
2WD/AWD position, the motor stops at that position.
The TCCM will not attempt to cross back over NEU-
TRAL if it does not have to. This means that there
was a block on the first attempt to go to 4H and the
transfer case has made it through NEUTRAL to a
known good position, then the motor will go back
only to the 2WD/4WD position and execute the
remainder of the attempts from there.
²For shifts out of NEUTRAL, any time a shift is
commanded out of NEUTRAL, the system needs to
get out. The TCCM should never go to NEUTRAL
unless the driver is commanding it and all required
conditions are being met
ENCODER DRIFT CORRECTION
Whenever a shift is completed, the TCCM stores
the position in memory as the transfer case's
intended position. The TCCM continuously monitors
the mode sensor and if the mode sensor drifts toward
into a NEUTRAL region sensor position for 2.0 sec-
onds, the TCCM will perform a motor drive to correct
the drift. The transfer case will be driven toward the
intended position for 1.0 seconds 100 msec. The
TCCM will wait for 2.0 seconds  50 msec. and repeat
the attempt to shift to the desired position. This will
continue until the intended position is reached.
SHIFT MOTOR BRAKING
Two modes of shift motor braking are employed to
improve shift performance, static and dynamic. Static
shift motor braking is utilized under the following
conditions:
²Whenever the transfer case is in the 2WD/AWD
or 4L 'D' channel position.²Whenever an invalid mode sensor code is
present.
Static motor braking is achieved by applying +12V
on both shift motor wires.
NOTE: Static Shift Motor Braking is independent of
ignition key position.
SHIFT ATTEMPT LIMIT
To protect the transfer case system, the TCCM will
impose a limit on the number of shifts that can occur
over a calibrated time period. The system will moni-
tor the number of 'D' channel segment transitions
that occur in any 30 second time period. If the num-
ber of segment transitions is 30 or greater, the sys-
tem will go into a default mode. The default mode of
operation for shifting is that the number of allowed
'D' channel transitions permitted to occur will be 3
over each 15 second  100 msec calibrated window of
time. After 5 minutes  100 msec, the motor can be
assumed to have cooled down and the system will
revert to normal operation. The following rules also
apply to the shift limit:
²The attempt limit will not prevent shifts coming
out of NEUTRAL, they will be allowed regardless of
the counter/timer.
²Any shift that is in progress when the counter
reaches a maximum count in time will be allowed to
complete before the default mode is entered. D-chan-
nel transitions during this period will not be counted
towards the default mode limit.
²A block, regardless of the direction, whether
towards destination or back towards reversal target
(shift timer expiring), will count as a value of 2 tran-
sitions towards the 30 segment transitions to go into
default mode as defined above. Current attempt limit
values are 30 transitions in 30 seconds and default
mode values are 3 transitions every 15 seconds for 5
minutes.
DRELECTRONIC CONTROL MODULES 8E - 19
TRANSFER CASE CONTROL MODULE (Continued)