1-78
ENGINE <TURBO>
-
Control System
DIAGNOSTIC SYSTEM
DESCRIPTION OF
OBD-II
SYSTEM
The engine control module (ECM) monitors its input/
output signals. Some signals are monitored all the
time, and others only under specified conditions.
When an irregularity has continued for a specified
time from when the irregular signal is initially moni-
tored, the engine control module judges that a fault
has occurred.
After detecting a fault, the engine control module
stores its diagnostic trouble code in memory when
it re-detects the same fault in an operation following
the next engine startup.
In regard to the items marked
*,
however, the engine
control module stores the diagnostic trouble code
of any of them the first time the module detects
it.
There are 35 diagnostic items, and the diagnostic
results can be read out with a scan tool.
Moreover, since memorization of the diagnostic
trouble codes is backed up directly by the battery,
the diagnostic results are memorized even if the
ignition key is turned off. The diagnostic trouble
codes will, however, be erased when the battery
terminal or the engine control module connector
is disconnected.
In addition, the diagnostic trouble code can be also
be erased by turning the ignition switch to ON and
sending the diagnostic trouble code erase signal
from the scan tool to the engine control module.
NOTE
If the sensor connector is disconnected with the
ignition switch turned on, the diagnostic trouble code
Data item
Engine coolant temperature
Engine speed
Vehicle speed
Long term fuel trim
Short term fuel trim
Fuel control state
Calculated load value
Diagnostic trouble code associated with the data in
memory
N716K7OAA
is memorized. In this case, send the diagnostic
trouble code erase signal from the scan tool to the
engine control module and the diagnostic memory
will be erased.
The 35 diagnostic items are provided as follows,
and if plural items are activated, they are all indicated
sequentially from the smallest code number.
NOTE
The diagnostic trouble code of ignition timing adjust-
ment signal is outputted when terminal for ignition
timing adjustment is grounded. Therefore, it is not
abnormal that the code is outputted even when ter-
minal for ignition timing adjustment is grounded for
ignition timing adjustment.
The engine control module stores in memory not
only the diagnostic trouble code of a fault but also
the intra-module RAM data on the engine operating
conditions that existed when it detected the fault.
(The data is called freeze frame data.)
The data shows the engine operating conditions
that existed when the engine control module de-
tected the fault as well as those that existed when
the module did not detect any fault.
However, when the engine control module detects
a misfiring or fuel trim malfunction, it clears the
existing data and stores the new data.
The data can be read by a scan tool and can be
conveniently used in performing fault repetition tests
for troubleshooting.
The data items to be stored in memory are shown
below.
Unit
“C
r/min.
km/h
%
%
0
Open loop
l
Closed loop
l
Open loop
-
drive condition
l
Open loop
-
DTC set
l
Closed loop
-
02
(rear)
trouble
%
-
ii
d
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