ESP CHRYSLER VOYAGER 2001 Service Manual

LEAK DETECTION PUMP MONITOR
The leak detection assembly incorporates two pri-
mary functions: it must detect a leak in the evapora-
tive system and seal the evaporative system so the
leak detection test can be run.
The primary components within the assembly are:
A three port solenoid that activates both of the func-
tions listed above; a pump which contains a switch,
two check valves and a spring/diaphragm, a canister
vent valve (CVV) seal which contains a spring loaded
vent seal valve.
Immediately after a cold start, between predeter-
mined temperature thresholds limits, the three port
solenoid is briefly energized. This initializes the
pump by drawing air into the pump cavity and also
closes the vent seal. During non test conditions the
vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia-
phragm which forces air out of the pump cavity and
into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow
in typical diaphragm pump fashion. The pump is con-
trolled in 2 modes:
Pump Mode:The pump is cycled at a fixed rate to
achieve a rapid pressure build in order to shorten the
overall test length.
Test Mode:The solenoid is energized with a fixed
duration pulse. Subsequent fixed pulses occur when
the diaphragm reaches the Switch closure point.
The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5º H20.
The cycle rate of pump strokes is quite rapid as the
system begins to pump up to this pressure. As the
pressure increases, the cycle rate starts to drop off. If
there is no leak in the system, the pump would even-
tually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .020º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP's solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle
rate is again interrogated and when it increases dueto the flow through the purge system, the leak check
portion of the diagnostic is complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system is
not functioning in some respect. The LDP is again
turned off and the test is ended.
DESCRIPTION - HIGH AND LOW LIMITS
The PCM compares input signal voltages from each
input device with established high and low limits for
the device. If the input voltage is not within limits
and other criteria are met, the PCM stores a diagnos-
tic trouble code in memory. Other diagnostic trouble
code criteria might include engine RPM limits or
input voltages from other sensors or switches that
must be present before verifying a diagnostic trouble
code condition.
OPERATION - SYSTEM
The Powertrain Control Module (PCM) monitors
many different circuits in the fuel injection, ignition,
emission and engine systems. If the PCM senses a
problem 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 warmup
cycles. Diagnostic trouble codes that affect vehicle
emissions illuminate the Malfunction Indicator Lamp
(MIL). Refer to Malfunction 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
circuit 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 (resulting in 0 volt input to the
PCM). Because the condition happens at an engine
25 - 8 EMISSIONS CONTROLRS
EMISSIONS CONTROL (Continued)

ON-BOARD DIAGNOSTICS
TABLE OF CONTENTS
page page
TASK MANAGER
DESCRIPTION...........................23OPERATION.............................23
TASK MANAGER
DESCRIPTION
The PCM is responsible for efficiently coordinating
the operation of all the emissions-related compo-
nents. The PCM is also responsible for determining if
the diagnostic systems are operating properly. The
software designed to carry out these responsibilities
is call the 'Task Manager'.
OPERATION
The Task Manager determines which tests happen
when and which functions occur when. Many of the
diagnostic steps required by OBD II must be per-
formed under specific operating conditions. The Task
Manager software organizes and prioritizes the diag-
nostic procedures. The job of the Task Manager is to
determine if conditions are appropriate for tests to be
run, monitor the parameters for a trip for each test,
and record the results of the test. Following are the
responsibilities of the Task Manager software:
²Test Sequence
²MIL Illumination
²Diagnostic Trouble Codes (DTCs)
²Trip Indicator
²Freeze Frame Data Storage
²Similar Conditions Window
Test Sequence
In many instances, emissions systems must fail
diagnostic tests more than once before the PCM illu-
minates the MIL. These tests are know as 'two trip
monitors.' Other tests that turn the MIL lamp on
after a single failure are known as 'one trip moni-
tors.' A trip is defined as 'start the vehicle and oper-
ate it to meet the criteria necessary to run the given
monitor.'
Many of the diagnostic tests must be performed
under certain operating conditions. However, there
are times when tests cannot be run because another
test is in progress (conflict), another test has failed
(pending) or the Task Manager has set a fault that
may cause a failure of the test (suspend).
²Pending
Under some situations the Task Manager will notrun a monitor if the MIL is illuminated and a fault is
stored from another monitor. In these situations, the
Task Manager postpones monitorspendingresolu-
tion of the original fault. The Task Manager does not
run the test until the problem is remedied.
For example, when the MIL is illuminated for an
Oxygen Sensor fault, the Task Manager does not run
the Catalyst Monitor until the Oxygen Sensor fault is
remedied. Since the Catalyst Monitor is based on sig-
nals from the Oxygen Sensor, running the test would
produce inaccurate results.
²Conflict
There are situations when the Task Manager does
not run a test if another monitor is in progress. In
these situations, the effects of another monitor run-
ning could result in an erroneous failure. If thiscon-
flictis present, the monitor is not run until the
conflicting condition passes. Most likely the monitor
will run later after the conflicting monitor has
passed.
For example, if the Fuel System Monitor is in
progress, the Task Manager does not run the EGR
Monitor. Since both tests monitor changes in air/fuel
ratio and adaptive fuel compensation, the monitors
will conflict with each other.
²Suspend
Occasionally the Task Manager may not allow a two
trip fault to mature. The Task Manager willsus-
pendthe maturing of a fault if a condition exists
that may induce an erroneous failure. This prevents
illuminating the MIL for the wrong fault and allows
more precis diagnosis.
For example, if the PCM is storing a one trip fault
for the Oxygen Sensor and the EGR monitor, the
Task Manager may still run the EGR Monitor but
will suspend the results until the Oxygen Sensor
Monitor either passes or fails. At that point the Task
Manager can determine if the EGR system is actu-
ally failing or if an Oxygen Sensor is failing.
MIL Illumination
The PCM Task Manager carries out the illumina-
tion of the MIL. The Task Manager triggers MIL illu-
mination upon test failure, depending on monitor
failure criteria.
RSON-BOARD DIAGNOSTICS25-23

TABLE OF CONTENTS - Continued
P1682-CHARGING SYSTEM VOLTAGE TOO LOW............................20
COMMUNICATION
P0600-PCM FAILURE SPI COMMUNICATIONS...............................23
P0601-PCM INTERNAL CONTROLLER FAILURE.............................23
P1685-WRONG OR INVALID KEY MSG RECEIVED FROM SKIM................24
P1686-NO SKIM BUS MESSAGE RECEIVED................................26
P1695-NO CCD/J1850 MESSAGE FROM BODY CONTROL MODULE............28
P1696-PCM FAILURE EEPROM WRITE DENIED.............................30
P1697-PCM FAILURE SRI MILE NOT STORED...............................30
P1698-NO BUS MESSAGE FROM TRANS CONTROL MODULE................32
*BUS +/- SIGNALS OPEN FROM SENTRY KEY IMMOBILIZER MODULE.........34
*NO RESPONSE FROM PCM (PCI BUS)....................................36
*NO RESPONSE FROM PCM (SCI ONLY)...................................37
*PCI BUS COMMUNICATION FAILURE.....................................40
DRIVEABILITY - GAS
P0071 - AMBIENT TEMP SENSOR PERFORMANCE..........................43
P0106-BAROMETRIC PRESSURE OUT OF RANGE..........................45
P0107-MAP SENSOR VOLTAGE TOO LOW.................................48
P0108-MAP SENSOR VOLTAGE TOO HIGH.................................51
P0117-ECT SENSOR VOLTAGE TOO LOW..................................54
P0118-ECT SENSOR VOLTAGE TOO HIGH.................................56
P0121-TPS VOLTAGE DOES NOT AGREE WITH MAP........................59
P0122-THROTTLE POSITION SENSOR VOLTAGE LOW.......................64
P0123-THROTTLE POSITION SENSOR VOLTAGE HIGH......................68
P0125-CLOSED LOOP TEMP NOT REACHED...............................71
P0131-1/1 O2 SENSOR SHORTED TO GROUND.............................73
P0137-1/2 O2 SENSOR SHORTED TO GROUND.............................73
P0132-1/1 O2 SENSOR SHORTED TO VOLTAGE............................76
P0138-1/2 O2 SENSOR SHORTED TO VOLTAGE............................76
P0133-1/1 O2 SENSOR SLOW RESPONSE.................................79
P0139-1/2 O2 SENSOR SLOW RESPONSE.................................79
P0134-1/1 O2 SENSOR STAYS AT CENTER.................................82
P0140-1/2 O2 SENSOR STAYS AT CENTER.................................82
P0135-1/1 O2 SENSOR HEATER FAILURE..................................85
P0141-1/2 O2 SENSOR HEATER FAILURE..................................88
P0171-1/1 FUEL SYSTEM LEAN...........................................90
P0172-1/1 FUEL SYSTEM RICH...........................................95
P0201-INJECTOR #1 CONTROL CIRCUIT..................................100
P0202-INJECTOR #2 CONTROL CIRCUIT..................................100
P0203-INJECTOR #3 CONTROL CIRCUIT..................................100
P0204-INJECTOR #4 CONTROL CIRCUIT..................................100
P0205-INJECTOR #5 CONTROL CIRCUIT..................................100
P0206-INJECTOR #6 CONTROL CIRCUIT..................................100
P0300-MULTIPLE CYLINDER MIS-FIRE....................................103
P0301-CYLINDER #1 MISFIRE...........................................103
P0302-CYLINDER #2 MISFIRE...........................................103
P0303-CYLINDER #3 MISFIRE...........................................103
P0304-CYLINDER #4 MISFIRE...........................................103
P0305-CYLINDER #5 MISFIRE...........................................103
P0306-CYLINDER #6 MISFIRE...........................................103
P0320-NO CRANK REFERENCE SIGNAL AT PCM...........................108
ii

TABLE OF CONTENTS - Continued
*CHECKING MAP SENSOR..............................................233
*CHECKING PCM POWER AND GROUND CIRCUITS........................234
*CHECKING RADIATOR FAN RELAY OUTPUT..............................235
*CHECKING THE A/C RELAY OUTPUT....................................236
*CHECKING TP SENSOR...............................................238
HEATING & A/C
P0645-A/C CLUTCH RELAY CKT.........................................239
P1598-A/C PRESSURE SENSOR VOLTS TOO HIGH.........................242
P1599-A/C PRESSURE SENSOR VOLTS TOO LOW.........................245
SPEED CONTROL
P1595-SPEED CONTROL SOLENOID CIRCUITS............................248
P1683-SPD CTRL PWR RELAY; OR S/C 12V DRIVER CKT...................248
STARTING
*ENGINE CRANKS DOES NOT START....................................253
*NO CRANK CONDITION................................................258
*NO RESPONSE FROM PCM WITH A NO START CONDITION................261
*START AND STALL CONDITION.........................................262
VEHICLE THEFT/SECURITY
ANTENNA FAILURE....................................................266
COP FAILURE.........................................................266
EEPROM FAILURE.....................................................266
INTERNAL FAULT......................................................266
RAM FAILURE.........................................................266
SERIAL LINK INTERNAL FAULT..........................................266
STACK OVERFLOW FAILURE............................................266
PCM STATUS FAILURE.................................................268
SERIAL LINK EXTERNAL FAULT.........................................268
ROLLING CODE FAILURE...............................................270
TRANSPONDER COMMUNICATION FAILURE..............................272
TRANSPONDER CYCLIC REDUNDANCY CHECK (CRC) FAILURE.............272
TRANSPONDER ID MISMATCH..........................................272
TRANSPONDER RESPONSE MISMATCH..................................272
VERIFICATION TESTS
VERIFICATION TESTS..................................................275
8.0 COMPONENT LOCATIONS..............................................283
8.1CONTROL MODULES AND FUSE & RELAY CENTER...................283
8.2CONTROLS AND SOLENOID.......................................283
8.3DATA LINK CONNECTOR..........................................285
8.4SENSORS.......................................................286
8.5FUEL SYSTEM...................................................288
8.6SWITCHES......................................................289
9.0 CONNECTOR PINOUTS................................................291
A/C COMPRESSOR CLUTCH - LT. GRAY 2 WAY............................291
A/C PRESSURE TRANSDUCER - GRAY 4 WAY.............................291
AIR TEMPERATRUE SENSOR - BLACK 2 WAY.............................291
iv

1.0 INTRODUCTION
The procedures contained in this manual include
specifications, instructions, and graphics needed to
diagnose the PCM Powertrain System. The diag-
nostics in this manual are based on the failure
condition or symptom being present at time of
diagnosis.
Please follow the recommendations below when
choosing your diagnostic path.
1. First make sure the DRBIIItis communicating
with the appropriate modules; ie., if the DRBIIIt
displays a No Response condition, you must
diagnose this first before proceeding.
2. Read DTC's (diagnostic trouble codes) with the
DRBIIIt.
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 system
schematics are in Section 10.0.
An * placed before the symptom description indi-
cates a customer complaint.
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. READ THIS DIAGNOSTIC
INFORMATION BEFORE TRYING TO DIAG-
NOSE A VEHICLE CODE. It is recommended that
you review the entire diagnostic information to
become familiar with all new and changed diagnos-
tic procedures.
If you have any comments or recommendations
after reviewing the diagnostic information, 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 the
following 2001 Town and Country; Caravan/Grand
Caravan; and Voyager/Grand Voyager vehicles
equipped with the 2.4L and the 3.3L/3.8L engines.
1.2 SIX-STEP TROUBLESHOOTING
PROCEDURE
Diagnosis of the powertrain control module
(PCM) is done in six basic steps:
²verification of complaint
²verification of any related symptoms
²symptom analysis
²problem isolation
²repair of isolated problem
²verification of proper operation
2.0 IDENTIFICATION OF
SYSTEM
The Powertrain Control Module (PCM) monitors
and controls:
²Fuel System
²Idle Air Control System
²Ignition System
²Charging System
²Speed Control System
²Cooling system
3.0 SYSTEM DESCRIPTION AND
FUNCTIONAL OPERATION
3.1 GENERAL DESCRIPTION
These Sequential Fuel Injection (SFI) engine sys-
tems have the latest in technical advances. The
on-board Euro Stage III OBD diagnostics incorpo-
rated with the Powertrain Control Module (PCM)
are intended to assist the field technician in repair-
ing vehicle problems by the quickest means.
3.2 FUNCTIONAL OPERATION
3.2.1 FUEL CONTROL
The PCM controls the air/fuel ratio of the engine
by varying fuel injector on time. Mass air flow is
calculated using the speed density method using
enigne speed, manifold absolute pressure, and air
temperature change.
Different fuel calculation strategies are used de-
pending on the operational state of the engine.
During crank mode, a prime shot fuel pulse is
delivered followed by fuel pulses determined by a
crank time strategy. Cold engine operation is deter-
mined via an open loop strategy until the O2
sensors have reached operating temperature. At
this point, the strategy enters a closed loop mode
where fuel requirements are based upon the state of
the O2 sensors, engine speed, MAP, throttle posi-
tion, air temperature, battery voltage, and coolant
temperature.
1
GENERAL INFORMATION

Euro Stage III OBD MONITOR INFORMATION
Comprehensive Major Monitors Major Monitors
Components Non Fuel Control Fuel Control
Monitor & Non Misfire & Misfire
Run constantly Run Once Per Trip Run Constantly
Includes All Engine Hardware Monitors Entire Emission Monitors Entire System
- Sensors, Switches, System
Solenoids, etc.
One Trip Faults - Turns On Two Trip Faults - Turns On Two Trip Faults - Turns On
The MIL and Sets DTC After The MIL and Sets DTC After The MIL and Sets DTC After
One Failure Two Consecutive Failures Two Consecutive Failures
Priority 3 Priority 1 or 3 Priority 2 or 4
All Checked For Continuity Done Stop Testing = Yes
Fuel Control Monitor
Open Monitors Fuel Control
Short To Ground Oxygen Sensor Heater System For:
Short To Voltage Oxygen Sensor Response
Fuel System Lean
Fuel System Rich
Inputs Checked For
Requires 3 Consecutive Rationality
Catalytic Converter
Fuel System Good TripsTo Efficiency Except EWMA
Extinguish The MIL Outputs Checked For - up to 6 tests per trip
Functionality and a one trip fault
EGR System
Misfire Monitor
Evaporative Emission Monitors For Engine Misfire
System at:
(Purge and Leak) 1000 RPM Counter
Non-LDP (Type B)
or **200 RPM Counter
LDP (Type A)
Requires 3 Consecutive Requires 3 Consecutive Requires 3 Consecutive
Global/Alternate Good Trips Global Good Trips Misfire Good Trips
to Extinguish the MIL* to Extinguish the MIL* To Extinguish the MIL
*40 Warm Up Cyclesare required to erase **Type A misfire is a two
DTC's
afterthe MIL has been extinguished. trip failure. The MIL will
illuminate and blink at
the first failure.
3
GENERAL INFORMATION

3.2.3 OTHER CONTROLS
CHARGING SYSTEM
The charging system is turned on when the
engine is started and ASD relay energized. When
the ASD relay is on, ASD output voltage is supplied
to the ASD sense circuit at the PCM. This voltage is
connected in some cases, through the PCM and
supplied to one of the generator field terminals
(Gen Source +). All others, the Gen field is con-
nected directly to the ASD output voltage. The
amount of current produced by the generator is
controlled by the Electronic Voltage Regulator
(EVR) circuitry, in the PCM. Battery temperature is
determined from IAT. This temperature along with
sensed line voltage, is used by the PCM to vary the
battery charging rate. This is done by cycling the
ground path to the other generator field terminal
(Gen field driver).
SPEED CONTROL SYSTEM
The PCM controls vehicle speed by operation of
the speed control servo vacuum and vent solenoids.
Energizing the vacuum solenoid applies vacuum to
the servo to increase throttle position. Operation of
the vent solenoid slowly releases the vacuum allow-
ing throttle position to decrease. A special dump
solenoid allows immediate release of throttle posi-
tion caused by braking, cruise control switch turned
off, shifting into neutral, excessive RPM (tires spin-
ning) or ignition off.
LEAK DETECTION PUMP SYSTEM (IF EQUIPPED)
The leak detection pump is a device that pressur-
izes the evaporative system to determine if there
are any leaks. When certain conditions are met, the
PCM will activate the pump and start counting
pump strokes. If the pump stops within a calibrated
number of strokes, the system is determined to be
normal. If the pump does not stop or stops too soon,
a DTC will be set.
3.2.4 PCM OPERATING MODES
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
wide open throttle. There are several different
modes of operation that determine how the PCM
responds to the various input signals.
There are two types of engine control operation:
open loopandclosed loop.
Inopen loopoperation, the PCM receives input
signals and responds according to preset program-
ming. Inputs from the heated oxygen sensors are
not monitored.Inclosed loopoperation, the PCM monitors the
inputs from the heated oxygen sensors. This input
indicates to the PCM whether or not the calculated
injector pulse width results in the ideal air-fuel
ratio of 14.7 parts air to 1 part fuel. By monitoring
the exhaust oxygen content through the oxygen
sensor, the PCM can fine tune injector pulse width.
Fine tuning injector pulse width allows the PCM to
achieve the lowest emission levels while maintain-
ing optimum fuel economy.
The engine start-up (crank), engine warm-up,
and wide open throttle modes are open loop modes.
Under most operating conditions, closed loop modes
occur with the engine at operating temperature.
IGNITION SWITCH ON (ENGINE OFF) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
1. The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic
fuel strategy.
2. The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input.
The PCM modifies fuel strategy based on this
input.
When the key is in the on position and the engine
is not running (zero rpm), the auto shutdown relay
and fuel pump relay are not energized. Therefore,
voltage is not supplied to the fuel pump, ignition
coil, and fuel injectors.
Engine Start-up ModeÐ This is an open loop
mode. The following actions occur when the starter
motor is engaged:
1. The auto shutdown and fuel pump relays are
energized. If the PCM does not receive the cam-
shaft and crankshaft signal within approxi-
mately one second, these relays are de-
energized.
2. The PCM energizes all fuel injectors until it
determines crankshaft position from the cam-
shaft and crankshaft signals. The PCM deter-
mines crankshaft position within one engine
revolution. After the camshaft position has been
determined, the PCM energizes the fuel injectors
in sequence. The PCM adjusts the injector pulse
width and synchronizes the fuel injectors by
controlling the fuel injectors' ground paths.
3. Once the engine idles within 64 rpm of its target
engine speed, the PCM compares the current
MAP sensor value with the value received dur-
ing the ignition switch on (zero rpm) mode. A
diagnostic trouble code is written to PCM mem-
ory if a minimum difference between the two
values is not found.
4
GENERAL INFORMATION

Once the auto shutdown and fuel pump relays
have been energized, the PCM determines the fuel
injector pulse width based on the following:
± engine coolant temperature
± manifold absolute pressure
± intake air temperature
± engine revolutions
± throttle position
The PCM determines the spark advance based on
the following:
± engine coolant temperature
± crankshaft position
± intake air temperature
± manifold absolute pressure
± throttle position
Engine Warm-Up Modeþ This is an open loop
mode. The PCM adjusts injector pulse width and
controls injector synchronization by controlling the
fuel injectors' ground paths. The PCM adjusts igni-
tion timing and engine idle speed. The PCM adjusts
the idle speed by controlling the idle air control
motor.
Cruise or Idle Modeþ When the engine is at
normal operating temperature, this is a closed loop
mode.
Acceleration Modeþ This is a closed loop mode.
The PCM recognizes an increase in throttle position
and a decrease in Manifold Vacuum as engine load
increases. In response, the PCM increases the in-
jector pulse width to meet the increased load. The
A/C compressor may be de-energized for a short
period of time.
Decelerationþ This is a closed loop mode. The
PCM recognizes a decrease in throttle position and
an increase in Manifold Vacuum as engine load
decreases. In response, the PCM decreases the
injector pulse width to meet the decreased load.
Full injector shut off may be obtained during high
speed deceleration.
Wide Open Throttle Modeþ This is an open
loop mode. The throttle position sensor notifies the
PCM of a wide open throttle condition. Once a wide
open throttle is sensed, the PCM de-energizes the
A/C compressor clutch relay for 20 seconds.
3.2.5 NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems, and conditions even though they could
have malfunctions that result in driveability prob-
lems. A diagnostic code may not be displayed for the
following conditions. However, problems with these
systems may cause a diagnostic code to be displayed
for other systems. For example, a fuel pressure
problem will not register a diagnostic code directly,
but could cause a rich or lean condition. This couldcause an oxygen sensor, fuel system, or misfire
monitor trouble code to be stored in the PCM.
Engine Timingþ The PCM cannot detect an
incorrectly indexed timing chain, camshaft
sprocket, or crankshaft sprocket. The PCM also
cannot detect an incorrectly indexed distributor.(*)
Fuel Pressureþ Fuel pressure is controlled by
the fuel pressure regulator. The PCM cannot detect
a clogged fuel pump inlet filter, clogged in-line filter,
or a pinched fuel supply.(*)
Fuel Injectorsþ The PCM cannot detect if a fuel
injector is clogged, the pintle is sticking, or the
wrong injectors are installed.(*)
Fuel Requirementsþ Poor quality gasoline can
cause problems such as hard starting, stalling, and
stumble. Use of methanol-gasoline blends may re-
sult in starting and driveability problems. See indi-
vidual symptoms and their definitions in Section
6.0 (Glossary of Terms).
PCM Groundsþ The PCM cannot detect a poor
system ground. However, a diagnostic trouble code
may be stored in the PCM as a result of this
condition.
Throttle Body Air Flowþ The PCM cannot
detect a clogged or restricted air cleaner inlet or
filter element.(*)
Exhaust Systemþ The PCM cannot detect a
plugged, restricted, or leaking exhaust system.(*)
Cylinder Compressionþ The PCM cannot de-
tect uneven, low, or high engine cylinder compres-
sion.(*)
Excessive Oil Consumptionþ Although the
PCM monitors the exhaust stream oxygen content
through the oxygen sensor when the system is in a
closed loop, it cannot determine excessive oil con-
sumption.
NOTE: ANY OF THESE CONDITIONS
COULD RESULT IN A RICH OR LEAN
CONDITION CAUSING AN OXYGEN SENSOR
TROUBLE CODE TO BE STORED IN THE
PCM, OR THE VEHICLE MAY EXHIBIT ONE
OR MORE OF THE DRIVEABILITY
SYMPTOMS LISTED IN THE TABLE OF
CONTENTS.
3.2.6 SKIS OVERVIEW
The Sentry Key Immobilizer System (SKIS) is
designed to prevent unauthorized vehicle opera-
tion. The system consists of a Sentry Key Immobi-
lizer Module (SKIM), ignition key(s) equipped with
a transponder chip and PCM. When the ignition
switch is turned on, the SKIM interrogates the
ignition key. If the ignition key is Valid or Invalid,
the SKIM sends a PCI Bus message to the PCM
indicating ignition key status. Upon receiving this
5
GENERAL INFORMATION

message the PCM will terminate engine operation,
or allow the engine to continue to operate.
3.2.7 SKIM ON-BOARD DIAGNOSTICS
The SKIM has been programmed to transmit and
monitor many different coded messages as well as
PCI Bus messages. This monitoring is called On
Board Diagnosis.
Certain criteria must be met for a diagnostic
trouble code to be entered into the SKIM memory.
The criteria may be a range of; Input voltage, PCI
Bus message, or coded messages to the SKIM. If all
of the criteria for monitoring a circuit or function
are met and a fault is sensed, a diagnostic trouble
code will be stored in the SKIM memory.
3.2.8 SKIS OPERATION
When ignition power is supplied to the SKIM, the
SKIM performs an internal self-test. After the self-
test is completed, the SKIM energizes the antenna
(this activates the transponder chip) and sends a
challenge to the transponder chip. The transponder
chip responds to the challenge by generating an
encrypted response message using the following:
Secret Key -This is an electronically stored
value (identification number) that is unique to each
SKIS. The secret key is stored in the SKIM, PCM
and all ignition key transponders.
Challenge- This is a random number that is
generated by the SKIM at each ignition key cycle.
The secret key and challenge are the two vari-
ables used in the algorithm that produces the
encrypted response message. The transponder uses
the crypto algorithm to receive, decode and respond
to the message sent by the SKIM. After responding
to the coded message, the transponder sends a
transponder I.D. message to the SKIM. The SKIM
compares the transponder I.D. to the available valid
key codes in the SKIM memory (8 key maximum at
any one time). After validating the key ignition the
SKIM sends a PCI Bus message called a Seed
Request to the engine controller then waits for a
PCM response. If the PCM does not respond, the
SKIM will send the seed request again. After three
failed attempts the SKIM will stop sending the seed
request and store a trouble code. If the PCM sends
a seed response, the SKIM sends a valid/invalid key
message to the PCM. This is an encrypted message
that is generated using the following:
VIN -Vehicle Identification Number
Seed -This is a random number that is generated
by the PCM at each ignition key cycle.
The VIN and seed are the two variables used in
the rolling code algorithm that encrypts the valid/
invalid key message. The PCM uses the rolling code
algorithm to receive, decode and respond to the
valid/invalid key message sent by the SKIM. Aftersending the valid/invalid key message the SKIM
waits 3.5 seconds for a PCM status message from
the PCM. If the PCM does not respond with a valid
key message to the SKIM, a fault is detected and a
trouble code is stored.
The SKIS incorporates a VTSS LED located on
the instrument panel upper cover. The LED re-
ceives switched ignition voltage and is hardwired to
the body control module. The LED is actuated when
the SKIM sends a PCI Bus message to the body
controller requesting the LED on. The body control-
ler then provides the ground for the LED. The
SKIM will request VTSS LED operation for the
following:
± bulb checks at ignition on
± to alert the vehicle operator to a SKIS mal-
function
± customer key programming mode
For all faults except transponder faults and VTSS
LED remains on steady. In the event of a transpon-
der fault the LED flashes at a rate of 1 Hz (once per
second). If a fault is present the LED will remain on
or flashing for the complete ignition cycle. If a fault
is stored in SKIM memory which prevents the
system from operating properly, the PCM will allow
the engine to start and run (for 2 seconds) up to six
times. After the sixth attempt, the PCM disables
the starter relay until the fault is corrected.
3.2.9 PROGRAMMING THE POWERTRAIN
CONTROL MODULE
Important Note:Before replacing the PCM for a
failed driver, control circuit or ground circuit, be
sure to check the related component/circuit integ-
rity for failures not detected due to a double fault in
the circuit. Most PCM driver/control circuit failures
are caused by internal failure to components (i.e.
12-volt pull-ups, drivers and ground sensors). These
failures are difficult to detect when a double fault
has occurred and only one DTC has set.
NOTE: IF THE PCM AND THE SKIM ARE
REPLACED AT THE SAME TIME, PROGRAM
THE VIN INTO THE PCM FIRST. ALL VEHICLE
KEYS WILL THEN NEED TO BE REPLACED
AND PROGRAMMED TO THE NEW SKIM.
The SKIS Secret Key is an I.D. code that is
unique to each SKIS. This code is programmed and
stored in the SKIM, engine controller and transpon-
der chip (ignition key). When replacing the PCM it
is necessary to program the secret key into the
PCM.
1. Turn the ignition on (transmission in park/
neutral).
2. Use the DRB and select THEFT ALARM, SKIM
then MISCELLANEOUS.
6
GENERAL INFORMATION

SYMPTOM DIAGNOSTIC TEST
POOR FUEL ECONOMY CHECKING PCM POWER AND GND CKT
CHECKING THE FUEL PRESSURE
CHECKING ECT SENSOR
CHECKING THROTTLE POSITION SENSOR
CHECKING MAP SENSOR
CHECKING IDLE AIR CONTROL MOTOR OPERATION
CHECKING IAT SENSOR
3.4 USING THE DRBIIIT
Refer to the DRBIIItuser 's guide for instructions
and assistance with reading DTC's, erasing DTC's,
and other DRBIIItfunctions.
3.5 DRBIIITERROR MESSAGES AND
BLANK SCREEN
Under normal operation, the DRBIIItwill dis-
play one of only two error messages:
± User-Requested WARM Boot or User-
Requested COLD Boot
ver: 2.14
date: 26 Jul93
file: key_itf.cc
date: Jul 26 1993
line: 548
err: 0x1
User-Requested COLD Boot
Press MORE to switch between this display
and the application screen.
Press F4 when done noting information.
3.5.1 DRBIIITDOES NOT POWER UP
If the LED's do not light or no sound is emitted at
start up, check for loose cable connections or a bad
cable. Check the vehicle battery voltage (data link
connector cavity 16). A minimum of 11 volts is
required to adequately power the DRBIIIt.
If all connections are proper between the
DRBIIItand the vehicle or other devices, and the
vehicle battery is fully charged, and inoperative
DRBIIItmay be the result of faulty cable or vehicle
wiring.
3.5.2 DISPLAY IS NOT VISIBLE
Low temperatures will affect the visibility of the
display. Adjust the contrast to compensate for this
condition
4.0 DISCLAIMERS, SAFETY,
WARNINGS
4.1 DISCLAIMERS
All information, illustrations, and specifications
contained in this manual are based on the latest
information available at the time of publication.
The right is reserved to make changes at any time
without notice.
4.2 SAFETY
4.2.1 TECHNICIAN SAFETY INFORMATION
WARNING: ENGINES PRODUCE CARBON
MONOXIDE THAT IS ODORLESS, CAUSES
SLOWER REACTION TIME, AND CAN LEAD
TO SERIOUS INJURY. WHEN THE ENGINE IS
OPERATING, KEEP SERVICE AREAS WELL
VENTILATED OR ATTACH THE VEHICLE
EXHAUST SYSTEM TO THE SHOP EXHAUST
REMOVAL SYSTEM.
Set the parking brake and block the wheels before
testing or repairing the vehicle. It is especially
10
GENERAL INFORMATION