Speed input JEEP GRAND CHEROKEE 2002 WJ / 2.G Owners Manual

(3) Install the wiring connector onto the input
speed sensor
(4) Verify the transmission fluid level. Add fluid as
necessary.
(5) Lower vehicle.
LINE PRESSURE (LP) SENSOR
DESCRIPTION
The TCM utilizes a closed-loop system to control
transmission line pressure. The system contains a
variable force style solenoid, the Pressure Control
Solenoid, mounted on the side of the solenoid and
pressure switch assembly. The solenoid is duty cycle
controlled by the TCM to vent the unnecessary line
pressure supplied by the oil pump back to the sump.
The system also contains a variable pressure style
sensor, the Line Pressure Sensor, which is a direct
input to the TCM. The line pressure solenoid moni-
tors the transmission line pressure and completes the
feedback loop to the TCM. The TCM uses this infor-
mation to adjust its control of the pressure control
solenoid to achieve the desired line pressure.
OPERATION
The TCM calculates the desired line pressure
based upon inputs from the transmission and engine.
The TCM calculates the torque input to the trans-
mission and uses that information as the primary
input to the calculation. The line pressure is set to a
predetermined value during shifts and when the
transmission is in the PARK and NEUTRAL posi-tions. This is done to ensure consistent shift quality.
During all other operation, the actual line pressure is
compared to the desired line pressure and adjust-
ments are made to the pressure control solenoid duty
cycle.
REMOVAL
(1) Raise vehicle.
(2) Place a suitable fluid catch pan under the
transmission.
(3) Remove the wiring connector from the line
pressure sensor (Fig. 83).
(4) Remove the bolt holding the line pressure sen-
sor to the transmission case.
(5) Remove the line pressure sensor from the
transmission case.
INSTALLATION
(1) Install the line pressure sensor into the trans-
mission case.
(2) Install the bolt to hold the line pressure sensor
into the transmission case. Tighten the bolt to 11.9
N´m (105 in.lbs.).
(3) Install the wiring connector onto the line pres-
sure sensor
(4) Verify the transmission fluid level. Add fluid as
necessary.
(5) Lower vehicle.
Fig. 82 Input Speed Sensor
1 - OUTPUT SPEED SENSOR
2 - LINE PRESSURE SENSOR
3 - INPUT SPEED SENSOR
Fig. 83 Line Pressure Sensor
1 - OUTPUT SPEED SENSOR
2 - LINE PRESSURE SENSOR
3 - INPUT SPEED SENSOR
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 245
INPUT SPEED SENSOR (Continued)

OUTPUT SPEED SENSOR
DESCRIPTION
The Input and Output Speed Sensors are two-wire
magnetic pickup devices that generate AC signals as
rotation occurs. They are mounted in the left side of
the transmission case and are considered primary
inputs to the Transmission Control Module (TCM).
OPERATION
The Input Speed Sensor provides information on
how fast the input shaft is rotating. As the teeth of
the input clutch hub pass by the sensor coil, an AC
voltage is generated and sent to the TCM. The TCM
interprets this information as input shaft rpm.
The Output Speed Sensor generates an AC signal
in a similar fashion, though its coil is excited by rota-
tion of the rear planetary carrier lugs. The TCM
interprets this information as output shaft rpm.
The TCM compares the input and output speed
signals to determine the following:
²Transmission gear ratio
²Speed ratio error detection
²CVI calculation
The TCM also compares the input speed signal and
the engine speed signal to determine the following:
²Torque converter clutch slippage
²Torque converter element speed ratio
REMOVAL
(1) Raise vehicle.
(2) Place a suitable fluid catch pan under the
transmission.
(3) Remove the wiring connector from the output
speed sensor (Fig. 96).
(4) Remove the bolt holding the output speed sen-
sor to the transmission case.
(5) Remove the output speed sensor from the
transmission case.
INSTALLATION
(1) Install the output speed sensor into the trans-
mission case.
(2) Install the bolt to hold the output speed sensor
into the transmission case. Tighten the bolt to 11.9
N´m (105 in.lbs.).
(3) Install the wiring connector onto the output
speed sensor
(4) Verify the transmission fluid level. Add fluid as
necessary.
(5) Lower vehicle.
OVERDRIVE SWITCH
DESCRIPTION
The overdrive OFF (control) switch is located in
the shifter handle. The switch is a momentary con-
tact device that signals the PCM to toggle current
status of the overdrive function.
OPERATION
At key-on, fourth and fifth gear operation is
allowed. Pressing the switch once causes the over-
drive OFF mode to be entered and the overdrive OFF
switch lamp to be illuminated. Pressing the switch a
second time causes normal overdrive operation to be
restored and the overdrive lamp to be turned off. The
overdrive OFF mode defaults to ON after the ignition
switch is cycled OFF and ON. The normal position
for the control switch is the ON position. The switch
must be in this position to energize the solenoids and
allow upshifts to fourth and fifth gears. The control
switch indicator light illuminates only when the over-
drive switch is turned to the OFF position, or when
illuminated by the transmission control module.
Fig. 96 Output Speed Sensor
1 - OUTPUT SPEED SENSOR
2 - LINE PRESSURE SENSOR
3 - INPUT SPEED SENSOR
21 - 254 AUTOMATIC TRANSMISSION - 545RFEWJ

STATOR
The stator assembly (Fig. 112) is mounted on a sta-
tionary shaft which is an integral part of the oil
pump. The stator is located between the impeller and
turbine within the torque converter case (Fig. 113).
The stator contains an over-running clutch, which
allows the stator to rotate only in a clockwise direc-
tion. When the stator is locked against the over-run-
ning clutch, the torque multiplication feature of the
torque converter is operational.
TORQUE CONVERTER CLUTCH (TCC)
The TCC (Fig. 114) was installed to improve the
efficiency of the torque converter that is lost to the
slippage of the fluid coupling. Although the fluid cou-
pling provides smooth, shock-free power transfer, it is
natural for all fluid couplings to slip. If the impeller
and turbine were mechanically locked together, a
zero slippage condition could be obtained. A hydraulic
piston with friction material was added to the tur-
bine assembly to provide this mechanical lock-up.
In order to reduce heat build-up in the transmission
and buffer the powertrain against torsional vibrations,
the TCM can duty cycle the L/R-CC Solenoid to achieve
a smooth application of the torque converter clutch.
This function, referred to as Electronically Modulated
Converter Clutch (EMCC) can occur at various times
depending on the following variables:
²Shift lever position
²Current gear range
²Transmission fluid temperature
²Engine coolant temperature
²Input speed
²Throttle angle
²Engine speed
Fig. 112 Stator Components
1 - CAM (OUTER RACE)
2 - ROLLER
3 - SPRING
4 - INNER RACE
Fig. 113 Stator Location
1-STATOR
2 - IMPELLER
3 - FLUID FLOW
4 - TURBINE
Fig. 114 Torque Converter Clutch (TCC)
1 - IMPELLER FRONT COVER
2 - THRUST WASHER ASSEMBLY
3 - IMPELLER
4-STATOR
5 - TURBINE
6 - PISTON
7 - FRICTION DISC
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 267
TORQUE CONVERTER (Continued)

OPERATION
The converter impeller (Fig. 115) (driving member),
which is integral to the converter housing and bolted
to the engine drive plate, rotates at engine speed.
The converter turbine (driven member), which reacts
from fluid pressure generated by the impeller, rotates
and turns the transmission input shaft.
TURBINE
As the fluid that was put into motion by the impel-
ler blades strikes the blades of the turbine, some of
the energy and rotational force is transferred into the
turbine and the input shaft. This causes both of them
(turbine and input shaft) to rotate in a clockwise
direction following the impeller. As the fluid is leav-
ing the trailing edges of the turbine's blades it con-
tinues in a ªhinderingº direction back toward the
impeller. If the fluid is not redirected before it strikes
the impeller, it will strike the impeller in such a
direction that it would tend to slow it down.
STATOR
Torque multiplication is achieved by locking the
stator's over-running clutch to its shaft (Fig. 116).
Under stall conditions (the turbine is stationary), the
oil leaving the turbine blades strikes the face of the
stator blades and tries to rotate them in a counter-
clockwise direction. When this happens the over-run-ning clutch of the stator locks and holds the stator
from rotating. With the stator locked, the oil strikes
the stator blades and is redirected into a ªhelpingº
direction before it enters the impeller. This circula-
tion of oil from impeller to turbine, turbine to stator,
and stator to impeller, can produce a maximum
torque multiplication of about 2.4:1. As the turbine
begins to match the speed of the impeller, the fluid
that was hitting the stator in such as way as to
cause it to lock-up is no longer doing so. In this con-
dition of operation, the stator begins to free wheel
and the converter acts as a fluid coupling.
TORQUE CONVERTER CLUTCH (TCC)
In a standard torque converter, the impeller and
turbine are rotating at about the same speed and the
stator is freewheeling, providing no torque multipli-
cation. By applying the turbine's piston and friction
material to the front cover, a total converter engage-
ment can be obtained. The result of this engagement
is a direct 1:1 mechanical link between the engine
and the transmission.
The clutch can be engaged in second, third, fourth,
and fifth gear ranges depending on overdrive control
switch position. If the overdrive control switch is in
the normal ON position, the clutch will engage after
the shift to fourth gear, and above approximately 72
km/h (45 mph). If the control switch is in the OFF
Fig. 115 Torque Converter Fluid Operation - Typical
1 - APPLY PRESSURE 3 - RELEASE PRESSURE
2 - THE PISTON MOVES SLIGHTLY FORWARD 4 - THE PISTON MOVES SLIGHTLY REARWARD
21 - 268 AUTOMATIC TRANSMISSION - 545RFEWJ
TORQUE CONVERTER (Continued)

position, the clutch will engage after the shift to
third gear, at approximately 56 km/h (35 mph) at
light throttle.
The TCM controls the torque converter by way of
internal logic software. The programming of the soft-
ware provides the TCM with control over the L/R-CC
Solenoid. There are four output logic states that can
be applied as follows:
²No EMCC
²Partial EMCC
²Full EMCC
²Gradual-to-no EMCC
NO EMCC
Under No EMCC conditions, the L/R Solenoid is
OFF. There are several conditions that can result in
NO EMCC operations. No EMCC can be initiated
due to a fault in the transmission or because the
TCM does not see the need for EMCC under current
driving conditions.
PARTIAL EMCC
Partial EMCC operation modulates the L/R Sole-
noid (duty cycle) to obtain partial torque converter
clutch application. Partial EMCC operation is main-
tained until Full EMCC is called for and actuated.
During Partial EMCC some slip does occur. Partial
EMCC will usually occur at low speeds, low load and
light throttle situations.
FULL EMCC
During Full EMCC operation, the TCM increases
the L/R Solenoid duty cycle to full ON after PartialEMCC control brings the engine speed within the
desired slip range of transmission input speed rela-
tive to engine rpm.
GRADUAL-TO-NO EMCC
This operation is to soften the change from Full or
Partial EMCC to No EMCC. This is done at mid-
throttle by decreasing the L/R Solenoid duty cycle.
REMOVAL
(1) Remove transmission and torque converter
from vehicle.
(2) Place a suitable drain pan under the converter
housing end of the transmission.
CAUTION: Verify that transmission is secure on the
lifting device or work surface, the center of gravity
of the transmission will shift when the torque con-
verter is removed creating an unstable condition.
The torque converter is a heavy unit. Use caution
when separating the torque converter from the
transmission.
(3) Pull the torque converter forward until the cen-
ter hub clears the oil pump seal.
(4) Separate the torque converter from the trans-
mission.
INSTALLATION
Check converter hub and drive flats for sharp
edges, burrs, scratches, or nicks. Polish the hub and
flats with 320/400 grit paper or crocus cloth if neces-
sary. Verify that the converter hub o-ring is properly
installed and is free from debris. The hub must be
smooth to avoid damaging the pump seal at installa-
tion.
(1) Lubricate oil pump seal lip with transmission
fluid.
(2) Place torque converter in position on transmis-
sion.
CAUTION: Do not damage oil pump seal or con-
verter hub o-ring while inserting torque converter
into the front of the transmission.
(3) Align torque converter to oil pump seal open-
ing.
(4) Insert torque converter hub into oil pump.
(5) While pushing torque converter inward, rotate
converter until converter is fully seated in the oil
pump gears.
(6) Check converter seating with a scale and
straightedge (Fig. 117). Surface of converter lugs
should be at least 13 mm (1/2 in.) to rear of straight-
edge when converter is fully seated.
(7) If necessary, temporarily secure converter with
C-clamp attached to the converter housing.
Fig. 116 Stator Operation
1 - DIRECTION STATOR WILL FREE WHEEL DUE TO OIL
PUSHING ON BACKSIDE OF VANES
2 - FRONT OF ENGINE
3 - INCREASED ANGLE AS OIL STRIKES VANES
4 - DIRECTION STATOR IS LOCKED UP DUE TO OIL PUSHING
AGAINST STATOR VANES
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 269
TORQUE CONVERTER (Continued)

However, evaporator capacity used to reduce the
amount of moisture in the air is not wasted. Wring-
ing some of the moisture out of the air entering the
vehicle adds to the comfort of the passengers.
Although, an owner may expect too much from their
air conditioning system on humid days. A perfor-
mance test is the best way to determine whether the
system is performing up to standard. This test also
provides valuable clues as to the possible cause of
trouble with the air conditioning system.
If the vehicle has the optional Automatic Zone Control
(AZC) system, and has intermittent operational prob-
lems or fault codes, be certain that the wire harness
connectors on the HVAC housing are properly seated
(Fig. 2). To check this condition, unplug the two wire
harness connector halves, then plug them in again.
Before performing the following procedure, (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMB-
ING - CAUTION) (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - WARNING). The air
temperature in the test room and in the vehicle must
be a minimum of 21É C (70É F) for this test.
(1)
Connect a tachometer and a manifold gauge set.
(2) If the vehicle has the standard manual temper-
ature control, set the A/C Heater mode control switch
knob in the Panel position, the temperature control
knob in the full cool (Fresh Air Mode) position, the
A/C button in the On position, and the blower motor
switch knob in the highest speed position. If the vehi-
cle has the optional AZC, set the A/C Heater mode
control switch knob in the Panel position, the tem-
perature control knob in the full cool position, the
A/C button in the On position, and the blower motor
switch knob in the highest (manual) speed position.
(3) Start the engine and hold the idle at 1,300 rpm
with the compressor clutch engaged.
(4) The engine should be at operating temperature.
The doors and windows must be open.
(5)
Insert a thermometer in the driver side center
A/C (panel) outlet. Operate the engine for five minutes.
(6) The compressor clutch may cycle, depending
upon the ambient temperature and humidity.(7) With the compressor clutch engaged, record the
discharge air temperature and the compressor dis-
charge pressure.
(8) Compare the discharge air temperature to the
Performance Temperature and Pressure chart. If the
discharge air temperature is high, (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
DIAGNOSIS AND TESTING - REFRIGERANT SYS-
TEM LEAKS) and (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE - REFRIGERANT SYSTEM CHARGE).
Performance Temperature and Pressure
Ambient Air Temperature
and Humidity21É C
(70É F @ 80%
humidity)27É C
(80É F @ 80%
humidity)32É C
(90É F @ 80%
humidity)38É C
(100ÉF@50%
humidity)43É C
110É F @ 20%
humidity)
Air Temperature at Center
Panel Outlet10 to 13É C
(50 to 55É F)14 to 17É C
(58 to 63É F)15 to 18É C
(60 to 65É F)17 to 20É C
(63 to 68É F)14 to 17É C
(58 to 63É F)
Evaporator Inlet Pressure
at Charge Port241 to 276 kPa
(35 to 40 psi)262 to 290 kPa
(38 to 42 psi)269 to 296 kPa
(39 to 43 psi)275 to 303 kPa
(40 to 44 psi)262 to 290 kPa
(38 to 42 psi)
Compressor Discharge
Pressure1241 to 1792
kPa
(180 to 260 psi)1380 to 1930
kPa
(200 to 280 psi)1380 to 1930
kPa
(200 to 280 psi)1655 to 2206
kPa
(240 to 320 psi)1567 to 2068
kPa
(220 to 300 psi)
Note: The discharge air temperatures will be lower if the humidity is less than the percentages shown.
Fig. 2 HVAC Housing - (rear view)
1 - Instrument Panel
2 - Air Intake
3 - Expansion Valve
4 - HVAC Housing
5 - Heater Core Input/Output Ports
6 - Instrument Panel Wiring Harness
7 - Blower Motor
WJHEATING & AIR CONDITIONING 24 - 3
HEATING & AIR CONDITIONING (Continued)

HISTORICAL FAULT CODES
Input faults 33 = IR thermister circuit was open
34 = IR thermister circuit was shorted
35 = Fan pot was shorted
36 = Fan pot was open
37 = Mode pot was shorted
38 = Mode pot was open
39 = IR sensor delta was too large
40 = Reserved
41 = Reserved
42 = One of four motor drivers had drive9A9shorted to
ground
43 = Engine air intake temperature Buss message
missing
44 = Country code Buss message missing
System Faults 45 = Mode motor was not responding
46 = AI (Recirc) motor was not responding
47 = Left temperature door was not responding
48 = Right temperature door was not responding
49 = Mode door travel range too small
50 = Mode door travel range too large
51 = AI (Recirc) door travel range too small
52 = AI (Recirc) door travel range too large
53 = Left temperature door travel too small
54 = Left temperature door travel too large
55 = Right temperature door travel too small
56 = Right temperature door travel too large
57 = Calibration check sum error
58 = Engine coolant temp bus message missing
59 = Vehicle speed bus message missing
60 = Engine RPM bus message missing
61 = OAT bus message missing
62 = Display intensity bus message missing
63 = VIN number bus message missing
64 = Raw OAT bus message was missing
65 = Reserved
66 = Reserved
67 = Reserved
NOTE: A battery disconnect will erase all faults
stored in Random Access Memory (RAM) of the
AZC control module. It is recommended that all
faults be recorded before they are erased.RETRIEVING FAULT CODES
(1) To begin the fault code tests, depress the A/C
and Recirc buttons at the same time and rotate the
left temperature control knob clockwise (CW) one
detent, then release the push-button.
24 - 20 CONTROLSWJ
A/C HEATER CONTROL (Continued)

(3) Check for continuity between each of the
blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and the
blower motor resistor or blower motor as required. If
not OK, replace the faulty blower motor resistor.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Depress locking tab and unplug the wire har-
ness connector from the blower motor resistor.
(3) Depress locking tab and unplug the resistor
connector from the blower motor.
(4) Remove the 2 screws that secure the blower
motor resistor to the HVAC housing.
(5) Remove the blower motor resistor from the
HVAC housing (Fig. 16).
INSTALLATION
(1) Install the blower motor resistor in the HVAC
housing. The housing is indexed to allow mounting in
only one position. Tighten the mounting screws to 2.2
N´m (20 in. lbs.).
(2) Plug in the wire harness connector to the
blower motor resistor.(3) Plug in the connector from the blower motor
resistor to the blower motor.
(4) Connect the battery negative cable.
BLOWER MOTOR SWITCH
DESCRIPTION
The A/C Heater blower motor is controlled by a
rotary-type blower motor switch, mounted in the A/C
Heater control panel. On vehicles with manual tem-
perature control systems, the switch allows the selec-
tion of four blower motor speeds, but will only
operate with the ignition switch in the On position
and the A/C Heater mode control switch in any posi-
tion, except Off. On vehicles with the Automatic Zone
Control (AZC) systems, the switch allows the selec-
tion of Lo Auto, Hi Auto, and ten speed settings
between Lo and Hi.
OPERATION
On manual temperature control systems, the
blower motor switch is connected in series with the
blower motor ground path through the a/c heater
mode control switch. The blower motor switch directs
this ground path to the blower motor through the
blower motor resistor wires, or directly to the blower
motor, as required to achieve the selected blower
motor speed.
On AZC systems, the blower motor switch is just
one of many inputs to the AZC control module. In the
manual blower modes, the AZC control module
adjusts the blower motor speed through the blower
motor controller as required to achieve the selected
blower switch position. In the auto blower modes, the
AZC control assembly is programmed to select and
adjust the blower motor speed through the blower
motor controller as required to achieve and maintain
the selected comfort level.
The blower motor switch cannot be repaired and, if
faulty or damaged, it must be replaced. The switch is
serviced only as a part of the a/c heater control
assembly.
DIAGNOSIS AND TESTING - BLOWER MOTOR
SWITCH-MANUAL TEMPERATURE CONTROL
SYSTEM
For circuit descriptions and diagrams, refer to the
appropriate wiring information.
Fig. 16 BLOWER MOTOR RESISTOR REMOVE/
INSTALL
1 - BLOWER MOTOR RESISTOR
2 - BLOWER MOTOR
3 - GROUND STRAP
4 - ELECTRICAL CONNECTORS
5 - HEATER CORE TUBES
24 - 28 CONTROLSWJ
BLOWER MOTOR RESISTOR BLOCK (Continued)

BLOWER MOTOR
DESCRIPTION
The blower motor and blower wheel are located in
the passenger side end of the HVAC housing, below
the glove box module. The blower motor controls the
velocity of the air flowing through the HVAC housing
by spinning a squirrel cage-type blower wheel within
the housing at the selected speed. The blower motor
and blower wheel can be serviced from the passenger
compartment side of the housing.
OPERATION
The blower motor will only operate when the igni-
tion switch is in the On position, and the a/c heater
mode control switch is in any position, except off. The
blower motor circuit is protected by a fuse in the
junction block. On models with the standard manual
temperature control system, the blower motor speed
is controlled by regulating the battery feed through
the blower motor switch and the blower motor resis-
tor. On models with the optional Automatic Zone
Control (AZC) system, the blower motor speed is con-
trolled by using Pulse Width Modulation (PWM). The
blower motor controller adjusts the battery feed volt-
age to the blower motor, based upon an input from
the blower motor switch, through the AZC control
module. Pulse width modulation of blower power
allows the blower to operate at any speed from sta-
tionary, to full speed.
The blower motor and blower motor wheel cannot
be repaired, and if faulty or damaged, they must be
replaced. The blower motor and blower wheel are
each serviced separately.
DIAGNOSIS AND TESTING - BLOWER MOTOR
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 AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
For circuit descriptions and diagrams, refer to the
appropriate wiring information. Possible causes of an
inoperative blower motor include:
²Faulty fuse²Faulty blower motor circuit wiring or wire har-
ness connections
²Faulty blower motor resistor (if the vehicle is so
equipped)
²Faulty blower motor controller (if the vehicle is
so equipped)
²Faulty blower motor switch
²Faulty a/c heater mode control switch
²Faulty blower motor.
Possible causes of the blower motor not operating
in all speeds include:
²Faulty fuse
²Faulty blower motor switch
²Faulty blower motor resistor (if the vehicle is so
equipped)
²Faulty blower motor controller (if the vehicle is
so equipped)
²Faulty AZC module (if the vehicle is so
equipped)
²Faulty blower motor circuit wiring or wire har-
ness connections.
VIBRATION
Possible causes of blower motor vibration include:
²Improper blower motor mounting
²Improper blower wheel mounting
²Blower wheel out of balance or bent
²Blower motor faulty.
NOISE
To verify that the blower is the source of the noise,
unplug the blower motor wire harness connector and
operate the HVAC system. If the noise goes away,
possible causes include:
²Foreign material in the HVAC housing
²Improper blower motor mounting
²Improper blower wheel mounting
²Blower motor faulty.
REMOVAL
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 AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
WJDISTRIBUTION 24 - 37

EMISSIONS CONTROL
TABLE OF CONTENTS
page page
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - EMISSION CONTROL
SYSTEM.............................1
DESCRIPTION - STATE DISPLAY TEST
MODE...............................2
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE...............................2
DESCRIPTION - DIAGNOSTIC TROUBLE
CODES..............................2DESCRIPTION - TASK MANAGER.........17
DESCRIPTION - MONITORED SYSTEMS . . . 17
DESCRIPTION - TRIP DEFINITION........19
DESCRIPTION - COMPONENT MONITORS . . 19
DESCRIPTION - NON-MONITORED
CIRCUITS...........................20
DESCRIPTION - HIGH AND LOW LIMITS . . . 20
DESCRIPTION - LOAD VALUE...........20
OPERATION - TASK MANAGER............21
EVAPORATIVE EMISSIONS................24
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - EMISSION CONTROL SYSTEM
The Powertrain Control Module (PCM) monitors
many different circuits in the fuel injection, ignition,
emission and engine systems. If the PCM senses a prob-
lem with a monitored circuit often enough to indicate an
actual problem, it stores a Diagnostic Trouble Code
(DTC) in the PCM's memory. If the code applies to a
non-emissions related component or system, and the
problem is repaired or ceases to exist, the PCM cancels
the code after 40 warm-up cycles. Diagnostic trouble
codes that affect vehicle emissions illuminate the Mal-
function Indicator (check engine) Lamp. Refer to Mal-
function Indicator Lamp in this section.
Certain criteria must be met before the PCM
stores a DTC in memory. The criteria may be a spe-
cific range of engine RPM, engine temperature,
and/or input voltage to the PCM.
The PCM might not store a DTC for a monitored cir-
cuit even though a malfunction has occurred. This may
happen because one of the DTC criteria for the circuit
has not been met.For example
,assume the diagnostic
trouble code criteria requires the PCM to monitor the
circuit only when the engine operates between 750 and
2000 RPM. Suppose the sensor's output circuit shorts to
ground when engine operates above 2400 RPM (result-
ing in 0 volt input to the PCM). Because the condition
happens at an engine speed above the maximum thresh-
old (2000 rpm), the PCM will not store a DTC.
There are several operating conditions for which
the PCM monitors and sets DTC's. Refer to Moni-
tored Systems, Components, and Non-Monitored Cir-
cuits in this section.Technicians must retrieve stored DTC's by connect-
ing the DRB scan tool (or an equivalent scan tool) to
the 16±way data link connector (Fig. 1).
NOTE: Various diagnostic procedures may actually
cause a diagnostic monitor to set a DTC. For
instance, pulling a spark plug wire to perform a
spark test may set the misfire code. When a repair
is completed and verified, connect the DRB scan
tool to the 16±way data link connector to erase all
DTC's and extinguish the MIL (check engine lamp).Fig. 1 Data Link (Diagnostic) Connector Location
1 - INSTRUMENT PANEL LOWER/LEFT EDGE
2 - DATA LINK CONNECTOR
WJEMISSIONS CONTROL 25 - 1