Chrysler Voyager. Manual — part 4

PCM sets a temporary fault (P1494) in memory, and
waits until the next time the Enabling Conditions
are met to run the test again. If this is again
detected, P1494 is stored and the MIL is illumi-
nated. If the problem is not detected during the next
enabling cycle, the temporary fault will be cleared.

However, if the PCM detects the reed switch open

when the key is turned to “ON”, the PCM must
determine if this condition is due to residual pres-
sure in the EVAP system, or an actual fault. The
PCM stores information in memory on EVAP sys-
tem purging from previous engine run or drive
cycles.

If little or no purging took place, residual pres-

sure could be holding the LDP diaphragm up,
causing the LDP switch to be open. Since this is not
a malfunction, the PCM cancels the EVAP Leak
Detection Test without setting the temporary fault.

If there was sufficient purging during the previ-

ous cycle to eliminate EVAP system pressure, the
PCM judges that this is a malfunction and sets a
temporary fault in memory. The next time that the
Enabling Conditions are met, the test will run
again. If the fault is again detected, the MIL will
illuminate and DTC 1494 will be stored. If the fault
is not detected, the temporary fault will be cleared.

FIGURE 6 SECTION 3

If no fault has been detected so far, the PCM

begins testing for possible blockage in the EVAP
system between the LDP and the fuel tank. This is
done by monitoring the time required for the LDP to
pump air into the EVAP system during two to three
pump cycles. If no blockage is present, the LDP
diaphragm is able to quickly pump air out of the
LDP each time the PCM turns off the LDP solenoid.
If a blockage is present, the PCM detects that the
LDP takes longer to complete each pump cycle. If
the pump cycles take longer than expected (approx-
imately 6 to 10 seconds) the PCM will suspect a
blockage. On the next drive when Enabling Condi-
tions are met, the test will run again. If blockage is
again detected, P1486 is stored, and the MIL is
illuminated.

FIGURE 6 SECTION 4

After the LDP blockage tests are completed, the

PCM then tests for EVAP system leakage. First, the
PCM commands the LDP to rapidly pump for 20 to
50 seconds (depending on fuel level) to build pres-
sure in the EVAP system. This evaluates the system
to see if it can be sufficiently pressurized. This
evaluation (rapid pump cycling) may occur several
times prior to leak checking. The LDP reed switch
does not close and open during rapid pumping
because the diaphragm does not travel through its
full range during this part of the test.

FIGURE 6 SECTION 5

Next, the PCM performs one or more test cycles

by monitoring the time required for the LDP reed
switch to close (diaphragm to drop) after the LDP
solenoid is turned off.

If the switch does not close, or closes after a long

delay, it means that the system does not have any
significant leakage and the EVAP Leak Detection
Test is complete.

However, if the LDP reed switch closes quickly,

there may be a leak or the fuel level may be low
enough that the LDP must pump more to finish
pressurizing the EVAP system. In this case, the
PCM will rapidly pump the LDP again to build
pressure in the EVAP system, and follow that by
monitoring the time needed for several LDP test
cycles. This process of rapid pumping followed by
several LDP test cycles may repeat several times
before the PCM judges that a leak is present.

When leaks are present, the LDP test cycle time

will be inversely proportional to the size of the leak.
The larger the leak, the shorter the test cycle time.
The smaller the leak, the longer the test cycle time.
DTC’s may be set when a leak as small as 0.5 mm
(0.020

9) diameter is present.

If the system detects a leak, a temporary fault

will be stored in PCM memory. The time it takes to
detect a .020, .040, or Large leak is based on
calibrations that vary from model to model. The
important point to remember is if a leak is again
detected on the next EVAP Leak Detection Test, the
MIL will illuminate and a DTC will be stored based
on the size of leak detected. If no leak is detected
during the next test, the temporary fault will be
cleared.

DIAGNOSTIC TIPS

During diagnosis, you can compare the LDP so-

lenoid activity with the monitor sequence in Figure
6. If the PCM detects a problem that could set a
DTC, the testing is halted and LDP solenoid activ-
ity will stop. As each section of the test begins, it
indicates that the previous section passed success-
fully. By watching to see which tests complete, you
can see if any conditions are present that the PCM
considers abnormal.

For example, if the LDP solenoid is energized for

the test cycles to test for blockage (P1486), it means
that the LDP has already passed its test for P1494.
Then, if the PCM detects a possible blockage, it will
set a temporary fault without turning on the MIL
and continue the leak portion of the test. However,
the PCM will assume that the system is already
pressurized and skip the rapid pump cycles.

Always diagnose leaks, if possible, before discon-

necting connections. Disconnecting connections
may mask a leak condition.

13

GENERAL INFORMATION

Keep in mind that if the purge solenoid seat is

leaking, it could go undetected since the leak would
end up in the intake manifold. Disconnect the purge
solenoid at the manifold when leak checking. In
addition, a pinched hose fault (P1486) could set if
the purge solenoid does not purge the fuel system
properly (blocked seat). The purge solenoid must
vent the fuel system prior to the LDP system test. If
the purge solenoid cannot properly vent the system
the LDP cannot properly complete the test for
P1486 and this fault can set due to pressure being
in the EVAP system during the test sequence.

Multiple actuation’s of the DRBIII

t Leak Detec-

tion Pump (LDP) Monitor Test can hide a 0.020 leak
because of excess vapor generation. Additionally,
any source for additional vapor generation can hide
a small leak in the EVAP system. Excess vapor
generation can delay the fall of the LDP diaphragm
thus hiding the small leak. An example of this
condition could be bringing a cold vehicle into a
warm shop for testing or high ambient tempera-
tures.

Fully plugged and partially plugged underhood

vacuum lines have been known to set MIL condi-
tions. P1494 and P0456 can be set for this reason.
Always, thoroughly, check plumbing for pinches or
blockage before condemning components.

TEST EQUIPMENT

The Evaporative Emission Leak Detector (EELD)

Miller Special Tool 8404 is capable of visually de-
tecting leaks in the evaporative system and will
take the place of the ultrasonic leak detector 6917A.
The EELD utilizes shop air and a smoke generator
to visually detect leaks down to 0.020 or smaller.
The food grade oil used to make the smoke includes
an UV trace dye that will leave telltale signs of the
leak under a black light. This is helpful when
components have to be removed to determine the
exact leak location. For detailed test manuals,
follow the operators instruction packaged with the
EELD.

IMPORTANT

Be sure that the PCM has the latest software

update. Reprogram as indicated by any applicable
Technical Service Bulletin. After LDP repairs are
completed, verify the repair by running the
DRBIII

t Leak Detection Pump (LDP) Monitor Test

as described in Technical Service Bulletin 18-12-99.

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 loop and closed loop.

In open loop operation, the PCM receives input

signals and responds according to preset program-
ming. Inputs from the heated oxygen sensors are
not monitored.

In closed loop operation, 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.

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 could
cause an oxygen sensor, fuel system, or misfire
monitor trouble code to be stored in the PCM.

Engine Timing − The PCM cannot detect an

incorrectly

indexed

timing

chain,

camshaft

sprocket, or crankshaft sprocket. The PCM also
cannot detect an incorrectly indexed distributor.(*)

Fuel Pressure − 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 Injectors − The PCM cannot detect if a fuel

injector is clogged, the pintle is sticking, or the
wrong injectors are installed.(*)

Fuel Requirements − 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 Grounds − 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.

14

GENERAL INFORMATION

Throttle Body Air Flow − The PCM cannot

detect a clogged or restricted air cleaner inlet or
filter element.(*)

Exhaust System − The PCM cannot detect a

plugged, restricted, or leaking exhaust system.(*)

Cylinder Compression − The PCM cannot de-

tect uneven, low, or high engine cylinder compres-
sion.(*)

Excessive Oil Consumption − 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
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. After
sending 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

15

GENERAL INFORMATION

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.

NOTE: After replacing the PCM, you must
reprogram pinion factor.

1. Turn the ignition on (transmission in park/

neutral).

2. Use the DRBIII

t and select THEFT ALARM,

SKIM then MISCELLANEOUS.

3. Select PCM REPLACED.

4. Enter secured access mode by entering the vehi-

cle four-digit PIN.

NOTE: If three attempts are made to enter
the secure access mode using an incorrect
PIN, secured access mode will be locked out
for one hour. To exit this lockout mode, turn
the ignition to the run position for one hour
then enter the correct PIN. (Ensure all
accessories are turned off. Also monitor the
battery state and connect a battery charger if
necessary).

5. Press ENTER to transfer the secret key (the

SKIM will send the secret key to the PCM).

3.2.10

PROGRAMMING THE SENTRY KEY
IMMOBILIZER MODULE

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.

1. Turn the ignition on (transmission in park/

neutral).

2. Use the DRBIII

t and select THEFT ALARM,

SKIM then MISCELLANEOUS.

3. Select SKIM MODULE REPLACEMENT (GAS-

OLINE).

4. Program the vehicle four-digit PIN into the

SKIM.

5. Select COUNTRY CODE and enter the correct

country.

NOTE: Be sure to enter the correct country
code.

If

the

incorrect

country

code

is

programmed into SKIM, the SKIM must be
replaced.

6. Select UPDATE VIN (the SKIM will learn the

VIN from the PCM).

7. Press ENTER to transfer the VIN (the PCM will

send the VIN to the SKIM).

8. The DRBIII

t will ask if you want to transfer the

secret key. Select ENTER to transfer secret key
from the PCM. This will ensure the current
vehicle ignition keys will still operate the SKIS
system.

3.2.11

PROGRAMMING THE IGNITION
KEYS TO THE SENTRY KEY
IMMOBILIZER MODULE

1. Turn the ignition on (transmission in park/

neutral).

2. Use the DRBIII

t and select THEFT ALARM,

SKIM, then MISCELLANEOUS.

3. Select PROGRAM IGNITION KEYS.

4. Enter secured access mode by entering the vehi-

cle four-digit PIN.

NOTE: A maximum of eight keys can be
learned to each SKIM AT ONE TIME. Once a
key is learned to a SKIM it (the key) cannot be
transferred to another vehicle.

If ignition key programming is unsuccessful, the

DRBIII

t will display one of the following messages:

16

GENERAL INFORMATION