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1.0 INTRODUCTION
The procedures contained in this manual include
all specifications, instructions and graphics needed
to diagnose engine control module (ECM) and sen-
try key immobilizer system (SKIS) problems; they
are no start, diagnostic trouble code (DTC) and no
trouble code problems for the ECM. The diagnostics
in this manual are based on the trouble condition or
symptom being present at the time of diagnosis.
When repairs are required, refer to the appropri-
ate service information for the proper removal and
repair procedure.
Diagnostic procedures change every year. New
diagnostic systems may be added; carryover sys-
tems may be enhanced. IT IS RECOMMENDED
THAT YOU REVIEW THE ENTIRE MANUAL TO
BECOME FAMILIAR WITH ALL NEW AND
CHANGED DIAGNOSTIC PROCEDURES.
This manual will cover all the necessary require-
ments to begin a logical diagnostic path for each
problem. If there is a diagnostic trouble code (DTC)
detected, go to the trouble code test. If there are no
DTCs present, go to a no trouble code (*), symptom
based test.
This book reflects many suggested changes from
readers of past issues. After using this book, if you
have any comments or recommendations, please fill
out the form at the back of the book and mail it back
to us.
1.1 SYSTEM COVERAGE
This diagnostic procedures manual covers all
2002 WG body vehicles equipped with the 2.7L
direct injection diesel engine.
1.2 SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the engine control module (ECM)
and sentry key immobilizer system (SKIS) is done
in six basic steps:
•
verification of complaint
•
verification of any related symptom
•
symptom analysis
•
problem isolation
•
repair of isolated problem
•
verification of proper operation
NOTE: All tests in this manual should be per-
formed with the engine at operating temperature,
unless specified within a particular test.
GENERAL INFORMATION
2.0 IDENTIFICATION OF
SYSTEM
The ECM is located in the left side of the engine
compartment attached to the left inner fender be-
hind the battery. The sentry key immobilizer mod-
ule (SKIM) is located below the steering column
behind the steering wheel.
3.0 SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1 GENERAL DESCRIPTION
The 2.7L direct injection diesel engine system is
equipped with the latest in technical advances. The
on-board diagnostics incorporated in the engine
control module and SKIM are intended to assist the
field technician in repairing vehicle problems by the
quickest means.
The engine system incorporates a common rail
fuel delivery design. This design utilizes electroni-
cally controlled solenoid valve type fuel injectors.
Each injector is controlled individually by the ECM.
Injector timing and fuel quantity are controlled by
the ECM based on inputs from the various sensors.
The precision control of the injectors by the ECM
helps to reduce the engine noise, odor and smoke.
3.2 FUNCTIONAL OPERATION
3.2.1 ECM ON-BOARD DIAGNOSTICS
The ECM has been programmed to monitor many
different circuits of the diesel fuel injection system.
This monitoring is called on-board diagnostics.
Certain criteria must be met for a trouble code to
be entered into the ECM memory. The criteria may
be a range of: engine rpm, engine temperature, time
or other input signals to the ECM. If all of the
criteria for monitoring a system or circuit are met,
and a problem is sensed, then a DTC will be stored
in the ECM memory.
It is possible that a DTC for a monitored circuit
may not be entered into the ECM memory, even
though a malfunction has occurred. This may hap-
pen when the monitoring criteria has not been met.
The ECM compares input signal voltages from
each input device with specifications (the estab-
lished high and low limits of the input range) that
are programmed into it for that device. If the input
voltage is not within the specifications and other
trouble code criteria are met, a DTC will be stored
in the ECM memory.
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