2002 DODGE RAM display

will return to the last function being displayed before
the ignition was turned to the Off position. With the
ignition switch in the On position, momentarily
depressing and releasing the Step push button switch
will cause the compass-mini-trip computer to change
its mode of operation, and momentarily depressing
and releasing the U.S./Metric push button will cause
the unit to toggle between U.S. and Metric measure-
ments. While in either compass mode, depressing the
U.S./Metric push button for more than ten seconds
will toggle the display between the compass/temper-
ature and the compass/compass in degrees modes.
This compass mini-trip computer features several
functions that can be reset. If both the Step and U.S./
Metric push buttons are depressed at the same time
with the ignition switch in the On position, the trip
computer information that can be reset is reset.
Depressing and releasing the Step and U.S./Metric
push buttons at the same time for more than 100
milliseconds, but not more than one second while in
any display mode (except the compass/temperature
mode) will cause a local reset. A local reset affects
only the function currently displayed. See the Reset
Chart below for more information on this feature.
Performing a local reset while in the compass/tem-
perature mode enters the module into the compass
variance setting mode.
Depressing and releasing the Step and U.S./Metric
push buttons at the same time for more than two
seconds while in any display mode (except the com-
pass/temperature mode) will cause a global reset. A
global reset changes all of the trip computer func-
tions that can be reset.
For more information on the features and control
functions of the compass mini-trip computer, see the
owner's manual in the vehicle glove box.
DIAGNOSIS AND TESTING - COMPASS
MINI-TRIP COMPUTER
If the problem with the compass mini-trip com-
puter module is an inoperative security indicator
lamp, refer toSecurity Indicator Lampin Vehicle
Theft/Security Systems. If the problem with the com-
pass mini-trip computer module is an ªOCº or ªSCº in
the compass/thermometer display, refer toAmbient
Temperature Sensorin this section. If the problem
with the compass mini-trip computer module is an
inaccurate or scrambled display, refer toCMTC Self-
Diagnostic Testin this section. If the problem with
the compass mini-trip computer module is incorrect
Vacuum Fluorescent Display (VFD) dimming levels,
use a DRBtscan tool and the proper Diagnostic Pro-
cedures manual to test for the correct dimming mes-
sage inputs being received from the instrument
cluster over the Chrysler Collision Detection (CCD)
data bus. If the problem is a no-display condition,use the following procedures. For complete circuit
diagrams, refer toOverhead Consolein the Con-
tents of Wiring Diagrams.
(1) Check the fused B(+) fuse in the junction block.
If OK, go to Step 2. If not OK, repair the shorted cir-
cuit or component as required and replace the faulty
fuse.
(2) Check for battery voltage at the fused B(+) fuse
in the junction block. If OK, go to Step 3. If not OK,
repair the open fused B(+) circuit to the battery as
required.
(3) Check the fused ignition switch output (run/
start) fuse in the junction block. If OK, go to Step 4.
If not OK, repair the shorted circuit or component as
required and replace the faulty fuse.
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) fuse in the junction block. If OK,
go to Step 5. If not OK, repair the open fused ignition
switch output (run/start) circuit to the ignition switch
as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the overhead console. Check for continuity
between the ground circuit cavities of the roof wire
harness connector for the overhead console and a
good ground. There should be continuity. If OK, go to
Step 6. If not OK, repair the open ground circuit to
ground as required.
(6) Connect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
roof wire harness connector for the overhead console.
If OK, go to Step 7. If not OK, repair the open fused
B(+) circuit to the junction block fuse as required.
(7) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (run/start) circuit cavity of the roof wire har-
ness connector for the overhead console. If OK, refer
toSelf-Diagnostic Testin the Diagnosis and Test-
ing section of this group for further diagnosis of the
compass mini-trip computer module and the CCD
data bus. If not OK, repair the open fused ignition
switch output (run/start) circuit to the junction block
fuse as required.
CMTC SELF-DIAGNOSTIC TEST
A self-diagnostic test is used to determine that the
compass mini-trip computer module is operating
properly electrically. Initiate the self-diagnostic test
as follows:
(1) With the ignition switch in the Off position,
simultaneously depress and hold the Step button and
the U.S./Metric button.
(2) Turn the ignition switch to the On position.
(3) Continue to hold both buttons depressed until
the compass mini-trip computer module enters the
8M - 10 MESSAGE SYSTEMSBR/BE
COMPASS/MINI-TRIP COMPUTER (Continued)

display segment test. In this test, all of the Vacuum
Fluorescent Display (VFD) segments are lighted
while the compass mini-trip computer module per-
forms the following checks:
²Microprocessor RAM read/write test
²Non-volatile memory read/write test
²Microprocessor ROM verification test
²CCD communications test.
(4) Following completion of these tests, the com-
pass mini-trip computer will display one of three
messages: ªPASS,º ªFAIL,º or ªCCd.º Respond to the
respective test results as follows:
²If the ªPASSº message is displayed, but compass
mini-trip computer operation is still improper, the
use of a DRB scan tool and the proper Diagnostic
Procedures manual are required for further diagno-
sis.
²If the ªFAILº message is displayed, the compass
mini-trip computer module is faulty and must be
replaced.
²If the ªCCdº message is displayed, the use of a
DRBtscan tool and the proper Diagnostic Proce-
dures manual are required for further diagnosis.
²If any VFD segment should fail to light during
the display segment test, the compass mini-trip com-
puter module is faulty and must be replaced.
(5) If all tests are passed, or if the ignition switch
is turned to the Off position, the compass mini-trip
computer module will automatically return to normal
operation.
NOTE: If the compass functions, but accuracy is
suspect, it may be necessary to perform a variation
adjustment. This procedure allows the compass
unit to accommodate variations in the earth's mag-
netic field strength, based on geographic location.
Refer to Compass Variation Adjustment in the Ser-
vice Procedures section of this group.
NOTE: If the compass reading has blanked out, and
only ªCALº appears in the display, demagnetizing
may be necessary to remove excessive residual
magnetic fields from the vehicle. Refer to Compass
Demagnetizing in the Service Procedures section of
this group.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the overhead console from the head-
liner (Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE - REMOVAL).
(3) Remove the three screws that secure the com-
pass mini-trip computer module to the overhead con-
sole housing (Fig. 7).(4) Pull the compass mini-trip computer module
away from the overhead console far enough to access
the wire harness connector.
(5) Disconnect the overhead console wire harness
connector from the compass mini-trip computer mod-
ule connector receptacle.
(6) Remove the compass mini-trip computer mod-
ule from the overhead console housing.
INSTALLATION
(1) Position the compass mini-trip computer mod-
ule onto the overhead console housing.
(2) Reconnect the overhead console wire harness
connector to the compass mini-trip computer module
connector receptacle.
(3) Install and tighten the three screws that secure
the compass mini-trip computer module to the over-
head console housing. Tighten the screws to 2.2 N´m
(20 in. lbs.).
(4) Install the overhead console onto the headliner
(Refer to 8 - ELECTRICAL/OVERHEAD CONSOLE -
INSTALLATION).
(5) Reconnect the battery negative cable.
NOTE: If a new compass mini-trip computer has
been installed, the compass will have to be cali-
brated and the variance set. Refer to Compass Vari-
ation Adjustment and Compass Calibration in the
Service Procedures section of this group for the
procedures.
Fig. 7 Overhead Console Compass Mini-Trip
Computer
1 - WIRE HARNESS CONNECTOR
2 - SCREWS (3)
3 - COMPASS MINI-TRIP COMPUTER MODULE
4 - FRONT LATCHES
BR/BEMESSAGE SYSTEMS 8M - 11
COMPASS/MINI-TRIP COMPUTER (Continued)

AMBIENT TEMP SENSOR
DESCRIPTION
Ambient air temperature is monitored by the com-
pass mini-trip computer module through the ambient
temperature sensor. The ambient temperature sensor
is a variable resistor mounted to a bracket that is
secured with a screw to the underside of the hood
panel near the hood latch striker in the engine com-
partment (Fig. 8).
For complete circuit diagrams, refer toOverhead
Consolein the Contents of Wiring Diagrams. The
ambient temperature sensor cannot be adjusted or
repaired and, if faulty or damaged, it must be
replaced.
OPERATION
The ambient temperature sensor is a variable
resistor that operates on a five-volt reference signal
sent to it by the compass mini-trip computer module.
The resistance in the sensor changes as temperature
changes, changing the return circuit voltage to the
compass mini-trip computer module. Based upon the
resistance in the sensor, the compass mini-trip com-
puter module senses a specific voltage on the return
circuit, which it is programmed to correspond to a
specific temperature.
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR
The thermometer function is supported by the
ambient temperature sensor, a wiring circuit, and a
portion of the compass mini-trip computer module. If
any portion of the ambient temperature sensor cir-
cuit fails, the compass/thermometer display function
will self-diagnose the circuit. If 55É C (131É F)
appears in the display, the sensor is being exposed to
temperatures above 55É C (131É F), or the sensor cir-
cuit is shorted. If ±40É C (±40É F) appears in the dis-
play, the sensor is being exposed to temperatures
below ±40É C (±40É F), or the sensor circuit is open.
The ambient temperature sensor circuit can also be
diagnosed using the following Sensor Test, and Sen-
sor Circuit Test. If the temperature sensor and cir-
cuit are confirmed to be OK, but the temperature
display is inoperative or incorrect, refer toDiagnosis
and Testing the Compass Mini-Trip Computer.
For complete circuit diagrams, refer toWiring Dia-
grams.
SENSOR TEST
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector.(2) Measure the resistance of the ambient temper-
ature sensor. At ±40É C (±40É F), the sensor resis-
tance is 336 kilohms. At 55É C (131É F), the sensor
resistance is 2.488 kilohms. The sensor resistance
should read between these two values. If OK, refer to
theSensor Circuit Test below. If not OK, replace
the faulty ambient temperature sensor.
SENSOR CIRCUIT TEST
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector and the overhead console wire har-
ness connector.
(2) Connect a jumper wire between the two termi-
nals in the body half of the ambient temperature sen-
sor wire harness connector.
(3) Check for continuity between the sensor return
circuit and the ambient temperature sensor signal
circuit cavities of the roof wire harness overhead con-
sole connector. There should be continuity. If OK, go
to Step 4. If not OK, repair the open sensor return
circuit or ambient temperature sensor signal circuit
to the ambient temperature sensor as required.
(4) Remove the jumper wire from the body half of
the ambient temperature sensor wire harness con-
nector. Check for continuity between the sensor
return circuit cavity of the roof wire harness over-
head console connector and a good ground. There
should be no continuity. If OK, go to Step 5. If not
OK, repair the shorted sensor return circuit as
required.
(5) Check for continuity between the ambient tem-
perature sensor signal circuit cavity of the roof wire
harness overhead console connector and a good
ground. There should be no continuity. If OK, refer to
Diagnosis and Testing the Compass Mini-Trip
Computerin this section. If not OK, repair the
shorted ambient temperature sensor signal circuit as
required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Locate the ambient temperature sensor, on the
underside of the hood near the hood latch striker
(Fig. 8).
(3) Disconnect the wire harness connector from the
ambient temperature sensor connector receptacle.
(4) Remove the one screw that secures the ambient
temperature sensor bracket to the inner hood rein-
forcement.
(5) Remove the ambient temperature sensor from
the inner hood reinforcement.
8M - 12 MESSAGE SYSTEMSBR/BE

(5) Remove three bolts retaining servo/servo
mounting bracket to side of battery tray (Fig. 5).
(6) Position servo assembly to gain access to 2
servo mounting nuts (Fig. 5) or (Fig. 6).
(7) Remove 2 mounting nuts holding servo cable
sleeve to bracket (Fig. 6).
(8) Pull speed control cable sleeve and servo away
from servo mounting bracket to expose cable retain-
ing clip (Fig. 6) and remove clip. Note: The servo
mounting bracket displayed in (Fig. 6) is a typical
bracket and may/may not be applicable to this model
vehicle.
(9) Remove servo from mounting bracket. While
removing, note orientation of servo to bracket.
Fig. 4 Servo LocationÐRemoval/Installation
1 - BATTERY TRAY
2 - SERVO ELECTRICAL CONNECTOR
3 - SERVO BRACKET SCREWS (3)
Fig. 5 Servo Mounting at Battery Tray
1 - BATTERY TRAY
2 - SPEED CONTROL SERVO
3 - SERVO MOUNTING NUTS (2)
Fig. 6 Servo Cable Clip Remove/InstallÐTypical
1 - SERVO MOUNTING NUTS (2)
2 - SERVO
3 - CABLE RETAINING CLIP
4 - SERVO CABLE AND SLEEVE
BR/BESPEED CONTROL 8P - 7
SPEED CONTROL SERVO (Continued)

(8) Disconnect servo cable at throttle body. Refer to
Servo Cable Removal/Installation in this group.
(9) Position battery tray up far enough for access
to speed control servo electrical connector and vac-
uum line.
(10) Disconnect electrical connector and vacuum
line at servo.
(11) Position battery tray with attached servo
assembly to gain access to 2 servo mounting nuts
(Fig. 5) or (Fig. 6).
(12) Remove 2 mounting nuts holding servo cable
sleeve to bracket (Fig. 6).
(13) Pull speed control cable sleeve and servo away
from servo mounting bracket to expose cable retain-
ing clip (Fig. 6) and remove clip. Note: The servo
mounting bracket displayed in (Fig. 6) is a typical
bracket and may/may not be applicable to this model
vehicle.
(14) Remove servo from mounting bracket. While
removing, note orientation of servo to bracket.
REMOVAL - DIESEL WITH AUTO. TRANS.
(1) Disconnect both negative battery cables at both
batteries.
(2) Disconnect positive battery cable at battery
(drivers side battery).
(3) Remove battery holddown bolts (Fig. 11).
(4) If equipped, pull up on battery heat shield to
remove it (Fig. 12).
(5) Remove battery from vehicle.
(6) From under vehicle, and in front of left front
wheelhouse, remove 2 lower battery tray nuts (Fig.
13).
(7) Remove 2 nuts and 2 bolts holding battery tray
to vehicle (Fig. 14).
(8) Remove cable cover (Fig. 15). Cable cover is
attached with 2 Phillips screws, 2 plastic retention
clips and 2 push tabs (Fig. 15). Remove 2 Phillips
screws and carefully pry out 2 retention clips. After
clip removal, push rearward on front tab, and
upward on lower tab for cover removal.
(9) Using finger pressure only, disconnect end of
servo cable from throttle lever pin by pulling forward
on connector while holding lever rearward (Fig. 16).
DO NOT try to pull connector off perpendicular
to lever pin. Connector will be broken.
Fig. 11 Battery Holddown Bolts
1 - REMOVE 2 BOLTS
2 - BATTERY HOLDDOWN STRAP
Fig. 12 Battery Heat Shield
1 - BATTERY HEAT SHIELD
Fig. 13 Battery Tray Lower Mounting Nuts
1 - BATTERY TRAY
2 - SPEED CONTROL SERVO
BR/BESPEED CONTROL 8P - 9
SPEED CONTROL SERVO (Continued)

(10) Position battery tray up far enough for access
to speed control servo electrical connector and vac-
uum line.
(11) Disconnect electrical connector (Fig. 17) and
vacuum line at servo.
(12) Position battery tray with attached servo
assembly to gain access to 2 servo mounting nuts
(Fig. 18) or (Fig. 19).
(13) Remove 2 mounting nuts holding servo cable
sleeve to bracket (Fig. 19).
(14) Pull speed control cable sleeve and servo away
from servo mounting bracket to expose cable retain-
ing clip (Fig. 19) and remove clip. Note: The servo
mounting bracket displayed in (Fig. 19) is a typical
bracket and may/may not be applicable to this model
vehicle.
(15) Remove servo from mounting bracket. While
removing, note orientation of servo to bracket.
Fig. 14 Battery Tray Upper Mounting Bolts/Nuts
1 - BATTERY TRAY
2 - REMOVE 2 BOLTS
3 - REMOVE 2 NUTS
Fig. 15 Cable/Lever/Throttle Linkage Cover
1 - CABLE/LEVER/LINKAGE COVER
2 - PUSH UP LOWER TAB
3 - SCREWS/CLIPS (2)
4 - TAB PUSH HERE
Fig. 16 Servo Cable at Throttle Lever
1 - PINCH (2) TABS
2 - CABLE MOUNTING BRACKET
3 - PINCH TABS (2)
4 - OFF
5 - THROTTLE CABLE
6 - THROTTLE LEVER
7 - THROTTLE LEVER PIN
8 - OFF
9 - CONNECTOR
10 - SPEED CONTROL CABLE
8P - 10 SPEED CONTROLBR/BE
SPEED CONTROL SERVO (Continued)

REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the headlamp and dash wire har-
ness connector for the washer pump/motor from the
motor connector receptacle (Fig. 3).
(3) Disconnect the washer hose from the barbed
outlet nipple of the washer pump/motor and allow
the washer fluid to drain into a clean container for
reuse.
(4) Using a trim stick or another suitable wide
flat-bladed tool, gently pry the barbed inlet nipple of
the washer pump out of the rubber grommet seal in
the reservoir. Care must be taken not to damage the
reservoir.
(5) Remove the rubber grommet seal from the
washer pump mounting hole in the washer reservoir
and discard.
INSTALLATION
(1) Install a new rubber grommet seal into the
washer pump mounting hole in the washer reservoir.
Always use a new rubber grommet seal on the reser-
voir.
(2) Position the barbed inlet nipple of the washer
pump to the rubber grommet seal in the reservoir.
(3) Press firmly and evenly on the washer pump
until the barbed inlet nipple is fully seated in the
rubber grommet seal in the washer reservoir mount-
ing hole.
(4) Reconnect the washer hose to the barbed outlet
nipple of the washer pump.(5) Reconnect the headlamp and dash wire harness
connector for the washer pump/motor unit to the
motor connector receptacle (Fig. 3).
(6) Refill the washer reservoir with the washer
fluid drained from the reservoir during the removal
procedure.
(7) Reconnect the battery negative cable.
WASHER RESERVOIR
DESCRIPTION
The molded plastic washer fluid reservoir is
secured with integral mounting tabs to keyed slots
on the left side of the radiator fan shroud in the left
front corner of the engine compartment. A bright yel-
low plastic filler cap with a rubber seal and an Inter-
national Control and Display Symbol icon for
ªWindshield Washerº and the text ªWasher Fluid
Onlyº molded into it snaps over the open end of the
filler neck. A bail strap that is integral to the cap
secures the cap to the reservoir filler neck when it is
removed for inspecting or adjusting the fluid level in
the reservoir. There are separate, dedicated holes on
the rear side of the reservoir provided for the mount-
ing of the washer/pump motor unit and the washer
fluid level switch.
The washer reservoir cannot be repaired and, if
faulty or damaged, it must be replaced. The washer
reservoir, the grommet seals for the washer pump/
motor unit and the washer fluid level switch, and the
filler cap are each available for service replacement.
OPERATION
The washer fluid reservoir provides a secure,
on-vehicle storage location for a large reserve of
washer fluid for operation of the washer system. The
washer reservoir filler neck provides a clearly
marked and readily accessible point from which to
add washer fluid to the reservoir. The washer/pump
motor unit is located in a sump area near the bottom
of the reservoir to be certain that washer fluid will
be available to the pump as the fluid level in the res-
ervoir becomes depleted. The washer fluid level
switch is mounted just above the sump area of the
reservoir so that there will be adequate warning to
the vehicle operator that the washer fluid level is
low, before the washer system will no longer operate.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Drain the engine cooling system. (Refer to 7 -
COOLING - STANDARD PROCEDURE - DRAIN/
ALL EXCEPT DIESEL ENGINE) or (Refer to 7 -
Fig. 3 Washer Reservoir
1 - FAN SHROUD
2 - LOW WASHER FLUID SENSOR
3 - WASHER PUMP
4 - WASHER RESERVOIR
8R - 10 WIPERS/WASHERSBR/BE
WASHER PUMP/MOTOR (Continued)

EMISSIONS CONTROL
TABLE OF CONTENTS
page page
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - DIESEL.................1
DESCRIPTION - STATE DISPLAY TEST
MODE...............................1
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE...............................2
DESCRIPTION - DIAGNOSTIC TROUBLE
CODES..............................2
DESCRIPTION - TASK MANAGER.........17
DESCRIPTION - MONITORED SYSTEMS . . . 17
DESCRIPTION - TRIP DEFINITION........19
DESCRIPTION - COMPONENT MONITORS -
GAS ENGINES.......................19DESCRIPTION - COMPONENT MONITORS -
DIESEL ENGINES.....................20
OPERATION
OPERATION - GAS ENGINES............20
OPERATION - DIESEL..................20
OPERATION - TASK MANAGER..........21
OPERATION - NON-MONITORED
CIRCUITS - GAS ENGINES..............24
OPERATION - NON-MONITORED
CIRCUITS - DIESEL....................24
AIR INJECTION.........................26
EVAPORATIVE EMISSIONS................32
EMISSIONS CONTROL
DESCRIPTION
DESCRIPTION - DIESEL
Two different modules are used for powertrain con-
trol with the diesel engine. The Powertrain Control
Module (PCM) is used primarily for charging system,
transmission, A/C compressor clutch operation and
speed control functions. The Engine Control Module
(ECM) is used to control thefuel and emissions
systems.The PCM is located in the right/rear of
engine compartment (Fig. 1). The ECM is bolted to
the left side of the engine cylinder block (Fig. 2).
DESCRIPTION - STATE DISPLAY TEST MODE
The switch inputs to the Powertrain Control Mod-
ule (PCM) have two recognized states; HIGH and
LOW. For this reason, the PCM cannot recognize the
difference between a selected switch position versus
an open circuit, a short circuit, or a defective switch.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire
switch circuit to the PCM functions properly. Connectthe DRB scan tool to the data link connector and
access the state display screen. Then access either
State Display Inputs and Outputs or State Display
Sensors.
Fig. 1 Powertrain Control Module (PCM) Location
1 - PCM MOUNTING BOLTS (3)
2 - POWERTRAIN CONTROL MODULE (PCM)
3 - (3) 32±WAY CONNECTORS
BR/BEEMISSIONS CONTROL 25 - 1