Chrysler PT Cruiser 2001 Service Manual Supplement page 2751

3.3 DIAGNOSTIC TROUBLE CODES
Diagnostic trouble code (DTC's) are codes stored
by the Transmission Control Module (TCM) that
helps us diagnose Transmission problems. They are
viewed using the DRBIII scan tool.
Always begin by performing a visual inspection of
the wiring, connectors, cooler lines and the trans-
mission. Any obvious wiring problems or leaks
should be repaired prior to performing any diagnos-
tic test procedures. Some engine driveability prob-
lems can be misinterpreted as a transmission prob-
lem. Ensure that the engine is running properly
and that no PCM DTC's are present that could
cause a transmission complaint.
If there is a communication bus problem, trouble
codes will not be accessible until the problem is
fixed. The DRBIII will display an appropriate
message. The following is a possible list of causes
for a bus problem:
– open or short to ground/battery in PCI bus
circuit (pin 43).
– internal failure of any module or component on
the bus.
Each diagnostic trouble code is diagnosed by
following a specific test sequence. The diagnostic
test procedures contain step-by-step instructions
for determining the cause of a transmission diag-
nostic trouble code. Possible sources of the code are
checked and eliminated one by one. It is not neces-
sary to perform all of the tests in this book to
diagnose an individual code. These tests are based
on the problem being present at the time that the
test is run. All testing should be done with a
fully charged battery.
If the TCM records a DTC that will adversely
affect vehicle emissions, it will request (via the
communication bus) that the PCM illuminate the
Malfunction Indicator Lamp (MIL). Although these
DTC's will be stored in the TCM immediately as a 1
trip failure, it may take up to five minutes of
accumulated trouble confirmation set the DTC and
illuminate the MIL. Three consecutive successful
EURO STAGE III OBD trips or clearing the DTC's
with a diagnostic tool (DRBIII or equivalent) is
required to extinguish the MIL. When the TCM
requests that the PCM illuminate the MIL, the
PCM sets a DTC ($89) to alert the technician that
there are DTC's in the TCM. This must also be
erased in the PCM in order to extinguish the MIL.
3.3.1 HARD CODE
Any Diagnostic Trouble Code (DTC) that is set
whenever the system or component is monitored is
a ''hard'' code. This means that the problem is there
every time the TCM checks that system or compo-
nent. Some codes will set immediately at start up
GENERAL INFORMATION
and others will require a road test under specific
conditions. It must be determined if a code is
repeatable (Hard) or intermittent before attempt-
ing diagnosis.
3.3.2 ONE TRIP FAILURES
A One Trip Failure, when read from the TCM, is
a hard EURO STAGE III OBD code that has not
matured for the full 5 minutes. This applies to codes
that will only set after 5 minutes of substituted gear
operation.
3.3.3 INTERMITTENT CODE
A diagnostic trouble code that is not there every
time the TCM checks the circuit or function is an
''intermittent'' code. Some intermittent codes, such
as codes: P-1792(12), P-1767(14), P-1768(15),
P-0725(18), P-1716(19), P-1781(21), P-1782(22),
P-1724(24), P-0705(28), P-0120(29), P-0750(41),
P-0755(42), P-0760(43), P-0765(44), P-1793(48),
P-0715(56), P-0720(57), P-1794(58), P-1796(70),
P-1799(74), P-1739(76), P-1717(77), P-0600(78) are
caused by wiring or connector problems. However
intermittent codes 50-54 are usually caused by
intermittent hydraulic seal leakage in the clutch
and/or accumulator circuits. Problems that come
and go like this are the most difficult to diagnose,
they must be looked for under the specific condi-
tions that cause them.
3.3.4 STARTS SINCE SET COUNTER
For the most recent code (Code 1), the Starts
Since Set counter counts the number of times the
vehicle has started since it was last set. The counter
will count up to 255 starts.
Note: that this code only applies to the last code set.
When there are no diagnostic trouble codes stored
in memory, the DRBIII will display ''NO DTC'S
PRESENT'' and the reset counter will show
''STARTS SINCE CLEAR = XXX''.
The number of starts helps determine if the
diagnostic trouble code is hard or intermittent.
– If the count is less than 3, the code is usually a
hard code.
– If the counter is greater than 3, it is considered
an intermittent code. This means that the
engine has been started most of the time
without the code recurring.
3.3.5 TROUBLE CODE ERASURE
A Diagnostic trouble code will be cleared from
TCM memory if it has not reset for 40 warm-up
cycles.
A warm-up cycle is defined as ''sufficient vehicle
operation such that the coolant temperature has
risen by at least 40°F from engine starting and
reaches a minimum temperature of 160°F''.
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