display NISSAN 300ZX 1984 Z31 Engine Fuel And Emission Control System Workshop Manual

SELF-DIAGNOSIS
Self-diagni
The self-diagnostic system determines malfunctions
of signal systems such as sensors, actuators, and
wire harnesses based on the status of the input
signals received by the
E C C S control unit
A malfunction is displayed by both the red and
green
L E D s (Light Emitting Diodes).
Basically, self-diagnosis
is always performed when
the power
is furnished to the E C C S control
unit The self-diagnosis results
are retained in the
memory chip of the
E C C S control unit and are
displayed only when the diagnosis mode selector
(located on
the side of the E C C S. control unit) is
turned fully clockwise
The self-diagnostic system
is provided with func-
tions which display malfunctions being checked
as well as those which are stored in the memory
In
this sense, it is very effective in determing an
"intermittent" malfunction The results which
is
or was stored in the memory can be erased by
following the steps specified
A malfunctioning area is determined by the num-
ber of blinks of both the
red and green L E D s
First, the red L E D blinks and the green follows
The red L E D refers to the tenth digit while the
green
one refers to the unit digit. For example,
when the red L
E D. blinks three times and the
green
L E.D blinks twice, this implies number
"32" In this way, all problems are classified by
code numbers.
inspection lamps1 Diagnosis mode
SEF6508
Judging the selfdiagnosis results
1 When the ignition switch is turned "ON",
the diagnostic system judges
a malfunction
tic System
until the specified input signal is entered and
detected
as 0 K
(These input signals are not stored in the
memory
)
1) Vehicle speed sensor circuit (VG30ET engine)
When the vehicle speed exceeds
10 km/h
(6 MPH) and its corresponding signal is entered
2) Throttle valve switch (idle switch) circuit,
neutral switch circuit (VG30ET engine) and
air
conditioner switch circuit
After the ignition switch
is turned "ON" and
"ON-OFF"
signals from each switch are
entered
3) Start signal
After the engine has started and when start
signals "ON" and then "OFF" are entered
2 After the self-diagnostic system has detected
a malfunction, it continues to provide a mal-
function display until the memory
is erased
properly by the sepcified steps
1) Crank angle sensor circuit
When 1" or 120" signal is not entered after
the engine has started
When either 1" or 120" signal is not entered
often enough
2) Air flow meter circuit
When the air flow meter produces an abnormal-
ly high output voltage with the engine off
When the air flow meter produces an abnormal-
ly low output voltage with the engine running.
3) Cylinder head temperature sensor circuit
When the cricuit
is shorted or open
4) Ignition signal
When an ignition signal
is not produced on the
primary winding of the ignition coil after
the
engine has started
5) Fuel pump circuit
When current flowing through the E
C C.S
control
unit to drive the fuel pump IS too
small or too large while the engine
is operating.
6) Detonation sensor circuit (VG30ET engine)
When the circuit
is shorted with the engine
operating
at a speed of above 2,000 rpms
When the circuit is shorted or open
7) Fuel temperature sensor circuit
EF & EC-35

SELF-DIAGNOSIS
-Self-diagnostic System (Cont'd)-
CAUTION.
a. Always turn the diagnosis mode selector
carefully using
a screwdriver Do not press
hard to turn. Otherwise, the selector may be
damaged
b. When the engine fails to start, crank the engine
more
than two seconds before starting the
self-diagnosing.
c. Before starting the self-diagnosing, do not erase
the stored memory. Doing
so will reduce
the self-diagnosis function considerably.
d. After a malfunctioning area has been corrected,
be sure to erase the memory
e. The self-diagnosed results are retained in the
memory by a small current flow from the
battery. Disconnecting the battery cable
or
the E.C.C.S.'s 15-pin connector erases the
memory stored. Always perform the
self-
diagnosing regarding "intermittent" checks
before disconnecting.
The crank
angle sensor signal plays an impor-
tant role in the E.C.C.S. A malfunctioning
sensor
is sometimes accompanied by a display
which shows malfunctions in other signal
systems.
In such a case, always start with
checking the crank angle sensor.
f
EF & EC-36

SELF-DIAGNOSIS
Self-diagnostic Procedure
fully counterclockwise -,
SEF651B
Turn Ignition switch to "ON" Poslflon1
Check harness for battery
source (Refer to page
EF &
EC-59, 8) If battery is
0 K , replace control unit
unit stay "ON" (Bulb check)
Turn diagnosis mode selector fully clockwise
Write down the malfunction- unit are displaying code No. 23, No 24
(VG30ET) and No 31.
I
SEF653B
ing code
SEF654B
unit are displaying code No 31
OK
Start engine 41
Make sure that N G Write down the malfunction-
unit are displaying code No 14 (VG30ET)
and No. 31 ing code
OK1
EF & EC-37

SELF-DIAGNOSIS
Self-diagnostic Procedure (Cont'd)
SEF655B
SEF6568
SEF651B
Drive vehde ax more than 10 kmlh (6 MPrll
(VG30ET eng.ne onov)
I 4
Make sure that inspection lamps on control
unit are displaying code
No 31
Write down the malfunction-
ing code
OK
Turn air conditioner switch
4
Write down the malfunction-
ing code
unit are displaying code No 44
OK
Turn diagnosis mode selector fully counter-
clockwise
4
Turn off engine 1
] See decoding chart (Pages EF & EC 39 - 42) I
(Pages EF & EC 43 - 53)
v
Erase the memorv of selfdiaanosis results
Procedure for memory erasure
Turn ignition switch to "ON" position
Turn diagnosis mode selector fully clockwise
and keep
it there for more than 2 seconds
Turn diagnosis mode selector fully counter-
clockwise and keep
it there for more than
2 seconds
Turn ignition switch to "OFF" position
EF & EC-38