Jeep XJ. Manual — part 530
ELECTRIC VACUUM MODULATOR (EVM)
The EVM (EGR Duty Cycle Solenoid) is mounted
behind the PCM.
REMOVAL
(1) Disconnect the negative battery cable.
(2) Disconnect two vacuum hoses at EVM (Fig. 3).
(3) Remove mounting screws of EVM (Fig. 3).
(4) Remove the EVM to gain access to the EVM
electrical connector.
(5) Remove electrical connector at EVM.
INSTALLATION
(1) Install electrical connector to EVM.
(2) Install EVM and tighten mounting screws (Fig.
3).
(3) Connect vacuum hoses (Fig. 3).
(4) Connect the negative battery cable.
SPECIFICATIONS
TORQUE CHART—2.5L DIESEL
Description
Torque
EGR Valve Mounting Bolts . . . 23 N·m (204 in. lbs.)
EGR Tube Mounting Bolts . . . 23 N·m (204 in. lbs.)
EVM Mounting Bolt . . . . . . . . . . 2 N·m (20 in. lbs.)
Fig. 3 Electric Vacuum Modulator (EVM)
1 – POWERTRAIN CONTROL MODULE (PCM)
2 – EVM HARNESS CONNECTOR
3 – ELECTRIC VACUUM MODULATOR (EVM)
4 – AIR CLEANER HOUSING
25 - 8
EMISSION CONTROL SYSTEM
XJ
REMOVAL AND INSTALLATION (Continued)
2000 JEEP CHEROKEE
1.0
INTRODUCTION
The procedures contained in this manual include
all the specifications, instructions, and graphics
needed to diagnose 2001 body system problems. The
diagnostics in this manual are based on the failure
condition or symptom being present at the time of
diagnosis.
Please follow the recommendations below when
choosing your diagnostic path.
1. First make sure the DRBIII
t is communicating
with the appropriate modules; i.e., if the
DRBIII
t displays a “No Response” condition, you
must diagnose that first.
2. Read DTC’s (diagnostic trouble codes) with the
DRBIII
t.
3. If no DTC’s are present, identify the customer
complaint.
4. Once the DTC or customer complaint is identi-
fied, locate the matching test in the Table of
Contents and begin to diagnose the symptom.
All component location views are in Section 8.0.
All connector pinouts are in Section 9.0. All sche-
matics are in Section 10.0.
An * placed before the symptom description indi-
cated a customer complaint.
When repairs are required, refer to the appropri-
ate service manual for the proper removal and
repair procedure.
Diagnostic procedures change every year. New diag-
nostic systems may be added: carryover systems may
be enhanced. READ THIS MANUAL BEFORE TRY-
ING TO DIAGNOSE A VEHICLE DIAGNOSTIC
TROUBLE CODE. It is recommended that you review
the entire manual to become familiar with all new and
changed diagnostic procedures.
This book reflects many suggested changes from
readers of past issues. After using this book, if you
have any comments or suggestions, please fill out
the back of the book and mail it back to us.
1.1
SYSTEM COVERAGE
This diagnostic manual covers 2001 Jeep Chero-
kee (XJ) vehicles.
1.2
SIX STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the body system is done in six basic
steps:
•
Verification of complaint
•
Verification of any related symptoms
•
Symptom analysis
•
Problem isolation
•
Repair of isolated problem
•
Verification of proper operation
2.0
IDENTIFICATION OF
SYSTEM
The vehicle systems that are part of the “body”
system are:
•
Airbag System (ACM)
•
Compass Mini-Trip Computer (CMTC)
•
Mechanical Instrument Cluster (MIC)
•
Remote Keyless Entry (RKE)
•
Vehicle Communication
3.0
SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
The body system on the 2001 Jeep Cherokee
consists of five modules that communicate over the
CCD bus (Chrysler Collision Detection multiplex
system). There are two additional modules, the
Powertrain Control Module (PCM) and the Trans-
mission Control Module (TCM) that are not part of
the body system, but do utilize the CCD bus for
communication. The TCM also utilizes the bus for
diagnostics. The PCM sends and receives messages
on the CCD bus; however, diagnostics are per-
formed through the Serial Communication Inter-
face or SCI, the same as last year. All of the
information about the functioning of all the systems
is organized, controlled and communicated by the
CCD bus, described in Section 3.6 (Vehicle Commu-
nication) of this general information.
Through the CCD bus, information about the
operation of vehicle components and circuits is
relayed quickly to the appropriate module(s). All
modules receive all the information transmitted on
the bus although a module may not require all
information to perform its function. Each module
will only respond to messages “addressed” to it
through a binary coding process. This method of
data transmission significantly reduces the com-
plexity of the wiring in the vehicle and the size of
wiring harnesses.
When replacing a blown fuse, it is important to
use only a fuse having the correct amperage rating.
The use of a fuse with a rating other than indicated
may result in a dangerous electrical system over-
load. If a properly rated fuse continues to blow, it
indicates a problem in the circuit that must be
corrected.
When replacing any bulbs, do not touch the new
bulb with your fingers. Oil contamination will se-
1
GENERAL INFORMATION
verely shorten bulb life. If the new bulb comes in
contact with an oily surface, clean the bulb with
rubbing alcohol.
3.1
AIRBAG SYSTEM
A dual front airbag system is a standard equip-
ment safety feature on this model. The airbag
system is designed to provide increased driver and
passenger protection if the vehicle is involved in a
front-end collision. A DRBIII
t scan tool is required
for diagnosis of the airbag system. The system is the
most effective when used in conjunction with the
seat belt system. The airbag system consists of the
Airbag Control Module (ACM), Mechanical Instru-
ment Cluster (MIC), driver and hybrid passenger
airbag module, clock spring, data link connector
and the Chrysler Collision Detection multiplex sys-
tem (CCD bus). There are no external impact sen-
sors in this system.
The ACM is an electronic module that monitors
the airbag system for proper operation, stores Di-
agnostic Trouble Codes (DTCs), controls the airbag
warning lamp, and contains an energy storage
capacitor. This capacitor stores enough electrical
energy to deploy the airbags for up to one second
following a battery disconnect or failure during an
impact. The purpose of the capacitor is to provide
airbag system protection in a severe secondary
impact if the initial impact has damaged or discon-
nected the battery, but was not severe enough to
deploy the airbag.
The ACM is mounted on the center tunnel floor
pan of the vehicle, behind the parking brake mech-
anism. The ACM provides DTCs to the technician
through the DRBIII
t via the CCD bus. Some cir-
cuits are tested continuously; others are checked
only under certain circumstances. The Mechanical
Instrument Cluster (MIC) turns the warning lamp
on or off based on CCD bus messages from the ACM.
The ACM cannot be repaired and must be replaced
if it is damaged or faulty.
THE AIRBAG SYSTEM IS A SENSITIVE,
COMPLEX
ELECTROMECHANICAL
UNIT.
BEFORE ATTEMPTING TO DIAGNOSE OR
SERVICE ANY AIRBAG SYSTEM OR RE-
LATED STEERING WHEEL, STEERING COL-
UMN OR INSTRUMENT PANEL COMPO-
NENTS, YOU MUST FIRST DISCONNECT
AND ISOLATE THE BATTERY NEGATIVE
(GROUND) CABLE. WAIT TWO MINUTES
FOR THE SYSTEM CAPACITOR TO DIS-
CHARGE BEFORE FURTHER SYSTEM SER-
VICE. THIS IS THE ONLY SURE WAY TO
DISABLE THE AIRBAG SYSTEM. FAILURE
TO DO THIS COULD RESULT IN ACCIDEN-
TAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
NEVER STRIKE OR KICK THE AIRBAG
CONTROL MODULE BECAUSE IT CAN DAM-
AGE THE IMPACT SENSOR OR AFFECT ITS
CALIBRATION. IF AN AIRBAG CONTROL
MODULE
IS
ACCIDENTALLY
DROPPED
DURING SERVICE, THE MODULE MUST BE
SCRAPPED AND REPLACED WITH A NEW
UNIT.
The deceleration or g-force resulting from the
impact of a front-end collision causes the safing
sensor inside the ACM to close. As soon as the ACM
internal accelerometer and the safing sensor are
closed an electrical charge is sent to the airbag
module. This causes the inflator to be actuated,
thus deploying the airbags. The total time from the
closure of the sensors to deployment and deflation
of the airbags is 1/10 of one second.
The AIRBAG warning lamp is the only point at
which “symptoms” of a system malfunction can be
observed by the customer. Whenever the ignition
key is turned to “run” or “start” position, the MIC
performs a lamp check by turning the AIRBAG
warning lamp on for six to eight seconds. If after
that the lamp turns off, it means that the ACM has
checked the system and found it to be free of
discernible malfunctions. If the lamp remains on,
there could be an active fault in the system or the
MIC lamp circuit may be defective. If the lamp
comes on and stays on for a period longer than six to
eight seconds and then goes off, there is usually an
intermittent problem in the system. The MIC mon-
itors the airbag warning lamp for an open or defec-
tive lamp driver circuit. This information is sent to
the ACM via a CCD bus message. The CCD bus
messages listed below can be monitored using
DRBIII
t and selecting “passive restraints,” “AIR-
BAG,” “MONITOR DISPLAY,” and “WARNING
LAMP STATUS.”
ACM LAMP REQUEST (on or off)
MIC BULB STATE (ok or failed)
MIC DRIVER STATE (ok or failed)
Perform the WARNING LAMP CIRCUIT OPEN
procedure in this book to find the cause of any
customer complaint regarding the AIRBAG warn-
ing lamp, such as:
•
Warning lamp does not illuminate
•
Warning lamp stays illuminated with no active
DTCs
2
GENERAL INFORMATION
NOTE: THE AIRBAG WARNING LAMP WILL
BE
ILLUMINATED
IF
THE
INSTRUMENT
CLUSTER
LOSES
CCD
BUS
COMMUNICATION
WITH
THE
AIRBAG
MODULE OR PCM. THE CCD BUS SYSTEM
MUST BE REPAIRED FIRST.
Service and general information labels about the
airbag system can be found on the driver’s sun
visor, and in the engine compartment.
To ensure that the airbag will be ready to deploy
in a collision, have the system serviced by an
authorized dealer.
IMPORTANT NOTE: IF THE POWERTRAIN
CONTROL MODULE HAS BEEN CHANGED
AND THE CORRECT VIN AND MILEAGE
HAVE NOT BEEN PROGRAMMED, A DTC
WILL BE SET IN THE AIRBAG MODULE. IN
ADDITION, IF THE VEHICLE IS EQUIPPED
WITH A SENTRY KEY IMMOBILIZER MODULE
(SKIM).
SECRET
KEY
DATA
MUST
BE
UPDATED TO ENABLE STARTING.
FOR AIRBAG SYSTEM:
ACTION:
1. Enter correct VIN and Mileage in PCM.
2. Erase codes in Airbag module.
DRIVER AIRBAG MODULE (DAB)
The Driver Airbag Module (DAB) protective trim
cover is the most visible part of the driver side
airbag system. The module is mounted directly to
the steering wheel. The protective trim cover is
fitted to the front of the airbag module and forms a
decorative cover in the center of the steering wheel.
Upon airbag deployment, this cover will split at a
predetermined breakout line. Located under the
airbag module trim cover are the horn switch, the
airbag cushion and the airbag cushion supporting
components. The airbag module includes a housing
to which the cushion and inflator are attached and
sealed. The airbag module cannot be repaired and
must be replaced if deployed or is damaged or
defective in any way. The inflator assembly is
mounted to the back of the airbag module. When
supplied with the proper electrical signal, the infla-
tor seals the hole in the airbag cushion so it can
discharge the gas it produces directly into the
cushion.
THE AIRBAG MODULE INFLATOR ASSEM-
BLY CONTAINS SODIUM AZIDE AND POTAS-
SIUM NITRATE. THESE MATERIALS ARE
POISIONOUS AND EXTREMELY FLAMMA-
BLE. CONTACT WITH ACID, WATER OR
HEAVY METALS MAY PRODUCE HARMFUL
OR IRRITATING GASES (SODIUM HYDROX-
IDE IS FORMED IN THE PRESENCE OF
MOISTURE)
OR
COMBUSTIBLE
COM-
POUNDS. IN ADDITION, THE PASSENGER
AIRBAG MODULE CONTAINS ARGON GAS
PRESSURIZED TO OVER 2500 PSI. DO NOT
ATTEMPT TO DISMANTLE AN AIRBAG MOD-
ULE OR TAMPER WITH ITS INFLATOR. DO
NOT PUNCTURE, INCINERATE OR BRING
INTO CONTACT WITH ELECTRICITY. DO
NOT STORE AT TEMPERATURES EXCEED-
ING 93°C (200°F).
The DAB is connected to the ACM through a
mechanical device called a clock spring. The clock-
spring allows the DAB to be hardwired through the
steering wheel to the ACM. A yellow quick discon-
nect connector is located under the steering column
at the lower edge of the knee blocker panel. This
connector when disconnected will disable both the
DAB and PAB modules.
THE AIRBAG SYSTEM IS A SENSITIVE,
COMPLEX
ELECTROMECHANICAL
UNIT.
BEFORE ATTEMPTING TO DIAGNOSE OR
SERVICE ANY AIRBAG SYSTEM OR RE-
LATED STEERING, STEERING COLUMN OR
INSTRUMENT PANEL COMPONENTS, YOU
MUST FIRST DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CA-
BLE. WAIT TWO MINUTES FOR THE SYSTEM
CAPACITOR TO DISCHARGE BEFORE FUR-
THER SYSTEM SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE AIRBAG SYS-
TEM. FAILURE TO DO THIS COULD RESULT
IN ACCIDENTAL DEPLOYMENT AND POSSI-
BLE PERSONAL INJURY. WHEN A STEER-
ING COLUMN HAS AN AIRBAG MODULE AT-
TACHED, NEVER PLACE THE COLUMN ON
THE FLOOR OR ON ANY OTHER SURFACE
WITH THE STEERING WHEEL OR AIRBAG
MODULE FACE DOWN.
PASSENGER AIRBAG MODULE (PAB)
The airbag door on the instrument panel above
the glove box is the most visible part of the passen-
ger side airbag system. Under the airbag door are
the airbag cushion and its supporting components.
The airbag module includes a housing to which the
cushion, inflator and canister of compressed gas are
attached and sealed. The airbag module cannot be
repaired and must be replaced if deployed or dam-
aged. The inflator seals the hole in the airbag
cushion so it can discharge the gas it produces
directly into the cushion when supplied with the
proper electrical signal. The airbag door is secured
to the airbag module and the instrument panel
base, and has predetermined breakout lines con-
cealed beneath its decorative cover. Upon airbag
deployment, the airbag door will split at the break-
out lines and the door will pivot out of the way. The
3
GENERAL INFORMATION
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