engine NISSAN GT-R 1998 Workshop Manual

TROUBLE DIAGNOSES
P ECM (aTCM) InputDutput Signal Reference
Value
SIGNAL VOLTAGES MEASURED WITH OSCILLOSCOPE AND CIRCUIT TESTER
- Signal voltages measured at ECM (-TCM) terminals (terminals for engine control) with a circuit tester and
example of waveforms displayed on an oscilloscope are shown below.
For signal terminals for A/T control, refer to "AIT Trouble Diagnosis" in AT section.
Measured data are affected by many factors such as irregularity of parts, vehicle history, operating
conditions, environment, service status, and measuring instruments and methods.
Terminal
No.
RX / TX
Signal name
I nition signal 8 ower transistor
drive signal)
CH~~"N
ECM & IGN coil
relay control signal (Data
link connector for CONSULT)
Tachometer drive
signal
NOTE: Above
At idle
When cranking: Approx. 0.1 2V
At idle: Approx. 0.1 V
?pprox. 1V
,During approx. 1.5
sec. after ignition switch turned OFF: 4pprox. 1 V 1.5 sec. after ignition switch turned OFF: Battery voltage)
:RB20DE
(UB),
RB25DEJ
Approx.
1.2V
:RB25DET]
Approx.
7.2V At
approx. 2,000 rpm
Approx. 0.15
- 0.25V
Approx. 3V
voltages are measured values obtained by analog circuit tester.
EC-39

TROUBLE DIAGNOSES
ECM (-TCM) InputlOutput Signal Reference
Value (Cont'd)
d
voltages are
Terminal No. Signal name
At idle At
approx. 2,000 rpm
Approx.
12V Approx. 8V
AAC valve control
signal
[RB20DE
(UB), RB25DEl
During 5 sec. after ignition switch tumed ON: Approx. 0.25V 5 sec. after ignition switch turned ON: Battery voltage
When cranking: Approx. 0.25V At idle: Approx. 0.25V Fuel pump relay
control signal - - [RB25DETJ
During 3 sec. after ignition switch tumed ON: Approx.
0.9V
3 sec. after ignition switch tumed ON: Battery voltage
When cranking: Approx. 0.9V At idle: Approx. 0.9V
Approx. 0.9V
Air conditioner
relay control signal Air conditioner
OFF: Battery voltage
Air conditioner ON: Approx. 0.25V
MIL OFF: Battery voltage
MIL ON
RBZODE
(UB), RB25DE: Approx. 0.85V RB25DET Approx. 0.1 V
Malfunction indica-
tor lamp
lgnition switch
(START) signal
Air conditioner
switch signal Approx.
OV (Ignition
switch at START Battery voltage)
Air conditioner OFF: Approx.
4.7V Air conditioner ON: Approx. 0.1 V -
22 (CHK) Check
(Diagnosis
start)
Throttle position
sensor signal
lgnition switch
(IGN) signal CONSULT
connected: Approx. OV CONSULT not connected: Approx. OV
Accelerator pedal released: Approx. OSV Accelerator pedal fully depressed: Approx. 4.2V
(Ignition switch ON, engine not running)
lgnition switch
OFF: Approx. OV lgnition switch ON: Battery voltage Approx.
0.6 - 0.7V
24
(IGN)
Ground Approx.
OV
Power
steering oil
pressure switch
signal Steering
wheel not tumed: Approx. 4.N Steering wheel turned: Approx. OV
26
NOTE: I bove measured values obtained by analog ircuit
tester.

TROUBLE DIAGNOSES
ECM (*TCM) InpuWOutput Signal Reference
Value (Cont'd)
Terminal
No.
41
NOTE: I
Signal name At
idle
rlehicle speed sen-
;or signal
dead lamp switch Light switch OFF: Approx. OV
;ignal
Light switch ON: Battery voltage
gnition power
sup- Ignition switch OFF: Approx. OV
)iY Ignition switch ON: Battery voltage
dle position switch
lB25DET.m
Mottle
opening Accelerator pedal released: Approx.
0.5V
ignal
Accelerator pedal fully depressed: Approx.
4.2V RB25DE.4WD.W
(Ignition switch ON, engine not running) ; RB25D€.AlT,
3R25Dm
Jeutral signal Selector lever in Neutral or in
N or P position: Approx. OV ParWNeutral posi- Selector lever in other positions: Approx. 4.8V
on switch)
:ull switch signal Accelerator pedal released: Approx. OV
?B20DE
(UB), Accelerator pedal fully depressed: Battery voltage
lB25DET-A/Tl (Ignition switch ON, engine not running)
- - - - -- - love voltages are measured values obtained by analog
At approx. 2,000 rpm
IRB20DE
(UB)] When driving at approx. 40 km/h: Approx. 2.4V @I
i ECL 1 7920
[RB25DE, RB25DETI
When driving at approx. 40
kmk: Approx. 2.4V %R
Approx. OV
(When accelerator pedal is depressed)
Approx.
0.N
rcuit tester.

TROUBLE DIAGNOSES
ECM (-TCM) Input/Output Signal Reference
Terminal No. Signal name
At approx. 2,000 rprn At idle
When cranking: Approx.
1.3V
Approx.
1.4V
ECLl426D
Crankshaft position
sensor 120" (REF) sig-
nal At idle: Approx. 1.35 - 1.4V
When cranking: Approx.
2.6V
Approx.
2.6V
Crankshaft position sensor 1" (POS) signal jle: Approx. 2.6V
ECLl428C
When cranking (DC range): Approx. (AC range): Approx.
DC range: Approx.
0.1V
AC range: Approx. 3.2V
Ring gear crankshaft
position sensor signal
[RB20DE
(UB)]
At idle DC range - Approx. 0.1 V [Ac range]. /\ppmx. 1 .W (v: 15 10 5 0
t (When engine raced sirddenly: Approx. 2.7 - 3.1V)
Turbo
Dressure
sensor
signal ' [RB25DET]
Throttle position sensor,
refrigerant pressure
sensor, turbo pressure
sensor power supply
Rear defogger switch
signal
-
49
NOTE: ,
2ear defogger switch OFF: Approx. OV
Rear defogger switch ON: Battery voltage
C-
bove voltages are measured values obtained by analog circuit tester.
EC-42

TROUBLE DIAGNOS
ECM (.TCM) lnpu
:s
3utput Signal Reference
Value (Cont'd)
.. No.
Fluctuates between approx. 0.1 to
0.4V and approx.
0.7 to
0.9V At
idle
- I I - I I -
I
I
- are measured
At approx. 2,000 rpm
:v: i .5 I .O 0.5 0
ECL 1 8645 11jllllllll ECL 1 8630
Throttle motor sensor
signal
[RB25DET'J Approx. 3.4V
I (Voltage becomes lower when TCS operates.)
Motor throttle switch
signal
[RB25DET]
Approx.
4.7V
Mass air flow sensor
signal
t
(When TCS is operating: Approx. OV)
Ignition switch ON: Approx.
0.2V
At idle: Approx.
1
.I - 1.2V Approx.
1.6 - 1.7V
Mass air flow sensor
ground Approx.
OV
I
Coolant temperature approx. 20°C: Approx. 3.5V
Coolant temperature approx.
80°C: Approx. 1.2V
Approx. 0.36V min.
(Voltage increases as the air conditioner refrigerant
pressure increases.)
Approx. 0.4
- 2V (') ': Voltage varies with measuring range (internal resis-
tame) of a circuit tester.
Battery voltage
C
+
+
+
56
-
62 1 Knock sensor signal 1
Engine coolant tem-
perature sensor signal
57
- -- -
63 1 Knock sensor signal 2
Refrigerant pressure
sensor
67 Control unit power
sup-
72
I PIY Receive (Data input to
control unit) 1
Transmit (Data output
from control unit) CONSULT
connected: Approx. 0.25V
CONSULT
not connected: Battery voltage
CONSULT connected: Approx.
9V max. CONSULT not connected: Approx. OV
C
Fan stopped: Battery voltage
Fan operating: Approx. 0.2 - 0.3V 78
NOTE: Above
Auxiliary electric fan
relay control signal
[RB25DE, RB25Dm
voltages values obtained
analog circuit
tester.

TROUBLE DIAGNOSES
ECM (-TCM) Input/Output Signal Reference
Terminal No.
108
- NOTE:
Signal name
CM.TCM, TCS/ABS
tegrated control signal
dultiplex communica-
&DE.m,
B25DETj
attery power supply
ijector drive signal
3attery voltage When cranking: Approx.
10.5V
Value (Cont'd)
(v) 50 40 30 20 10
0
At idle: &Wry voltage
A:
idle
Approx. 2V
rariable
air intake con-
:ol solenoid valve con- switch ON: Battery voltage (Solenoid valve
rot signal
RB20DE (UB), At idle: Approx. 0.2
- 0.3V (Solenoid valve ON) At
approx. 2,000
rpm
t
3B25DEI ' .
-urbo pressure control iO1enOid valve Battery voltage (Solenoid valve OFF)
iianal
4ir jet swirl sole- Coolant temperature below approx. 70°C: Approx.
0.9V (Solenoid valve ON)
'Oid Coolant temperature approx. 70°C and above: Battery
RB20DE (VB)] voltage (Solenold valve OFF)
[RB20DE (UB), RB25DEl
Air conditioner OFF: Battery voltage
Air conditioner ON: Battery voltage Approx.
10V
(After approx.
15 sec.)
Zanister
purge control
~alve
control signal
M 30 20 10 0
(Waveform indicates when air conditioner is
ON.)
[RB20DETJ
Air conditioner OFF: Battery voltage
Air conditioner ON: Battery voltage
4 Approx. 1OV
(After approx. 15 sec.) Slightly lower than battery voltage
t At
approx. 3,650 rpm and above [RB2ODE (UB)]
At approx. 3,500 rpm and above [RB25Dq : Battery voltage (Solenotd valve OFF)
t [When engine raced suddenly: Approx. 0.3V (Solenoid
valve ON)]
t Coolant temperature approx. 70°C and above, and
driving at approx. 3,300 rpm and above [MTT] Coolant temperature approx. 70°C and above, and
driving at approx. 3,000 rpm and above [A/T1 : Approx. 0.9V (Solenoid valve ON)
Approx.
9V
Approx. 9V
I (Waveform indicates when air conditioner is ON.)
tester.

TROUBLE DIAGNOSES
ECM (.TCM) InputlOutput Signal Reference
Value (Cont'd)
I Signal name
No. At
idle 7 At approx. 2,000 rpm
Control unit power sup-
ply (Counter-electromo-
live current feedback
circuit)
Fuel pump terminal
voltage control output
1 signal
IRB25DETI
Variable valve timing ,- control signal Battery voltage
Ignition switch at START: Approx.
OV During approx. 30 sec. after engine started with cool-
ant temperature 50°C or above: Approx. OV At idle: Approx. 1 OV
Battery voltage (Solenoid valve OFF)
Approx.
0.3V
Approx. OV
I t [With driving wheels lifted and gear in D position:
Approx. 0.45V (Solenoid valve ON)] AT
Approx. 0.3V (At approx. 2,800 rpm and above: Battery voltage) 1 I I
NOTE: Above voltages are measured values obtained by analogue circuit tester. BR

TROUBLE DIAGNOSES
System Description
Vehicle with RB20DE and RB25DET engine has TCM integrated into ECM. Vehicle with RB25DE engine has
TCM and ECM separately.
Fail-safe Function @ When malfunction occurs in each sensor and solenoid, the fail-safe functions below enable vehicle to be
driven.
VEHICLE SPEED SENSOR 1 (Output shaft speed sensor)
Inputs a signal from vehicle speed sensor in speedometer. EG
THROTTLE POSITION SENSOR
Detects throttle opening by idle switch and full switch, and controls line pressure as follows. I 1 I Idle switch
-
--
I
--
ON OFF I Minimum oil pressure I 0/8 ST
I
OFF OFF
Full switch
ON Maximum oil pressure
PNP SWITCH
When the multiple PNP switch signals are input to TCM and ECM-TCM, the priority of selector lever position I28
becomes as follows by internal TCM determination.
4AT D, N, R, 2, 1 I%$ M-AT D, N, R, 3, 2
Because the hydraulic circuit of the control valve is switched by manual valve according to the selector lever
position, however, actual operating condition of vehicle becomes as follows.
EL
I N I "N" and other position signals I N
Line pressure
218
P
R
- - -- pp - pp - -
4AT I D I "D" and other position signals I Dl*DP*Dd
Throttle opening I
418 BR
Running status
Actual lever position
1 "2 and other position signals I 21 ~22
PNP switch input signal
"P and other position signals
"R" and other position signals
--
r"2 and "1" 21 ~22
P 83
R
I 2 1 "2" and other position signals / 21 42
M -AT
3
L
1
P
R
N
D
"1" and other position signals
"P" and other position signals
"R" and other position signals
"N" and other position signals
"D" and other position signals
I
l,++l2
P
R
N
D1t;.D2c*D3
"3 and other position signals
"3" and "2" position signals
3, -3,-3-3,
3, +3, +3,

TROUBLE DIAGNOSES
Fail-safe Function (Cont'd)
SHIFT SOLENOID A, B
When a malfunctioning signal of solenoid is input to TCM and ECM-TCM, the gear is shifted as follows.
Normal Abnormal solenoid A Abnormal solenoid B Abnormal solenoid A/B Shift positions A B Gears A B Gears A I3 Gears A 8 Gears
0 0 1 st o-+x 03x - - - -
-- 0: Solenoid ON X: Solenoid OFF -: Abnormal
LINE PRESSURE SOLENOID
When a malfunctioning signal of solenoid is input to TCM and ECM-TCM, the line pressure solenoid is turned
OFF, and the line pressure is set to maximum oil pressure.
LOCK-UP SOLENOID
When a malfunctioning signal of solenoid is input to TCM and ECM.TCM, the lock-up solenoid is turned OFF,
and the lock-up
is released.
OVERRUN CLUTCH SOLENOID
When a malfunctioning signal of solenoid is input to TCM and ECM-TCM, the overrun clutch solenoid is turned
OFF, and the overrun clutch is engaged to apply the engine brake during deceleration.
MANUAL MODE SWITCH (M-AT)
When a malfunctioning signal of manual mode switch is input to TCM and ECM.TCM, the gear is controlled
with normal "D" position.
SHIFT CONTROL UNIT (Except RB20DE)
When a malfunction occurs in the shift control unit, the shift solenoid NB are turned OFF, and the gear posi-
tion
is controlled with 3rd speed.
TURBINE SENSOR (Except RB20DE)
Controlled by vehicle speed sensor 1 in the same way without turbine sensor

TROUBLE DIAGNOSES
Shift Mechanism
1 Turbine sensor 1
tine pressure solenoid I 1
Shift solenoid B
Full switch
ECM-TCM
(All side) (RB20DE, RB25DET) or TCM (RB25DE) p-
ECM.TCM (Engine side) * I
(RB20DE. RB25DET) or Venrle speed sensor 2
ECM (RB25DE) ,
1 (RB25DET)
POWER ~nd~calor lamp @AT;
( POWER (Except M-AT) ] 1 SNOW I
Shift control unit
(Except RB20DE)
Overdrive control switch
I
O/D OFF
indicator lamp
Steering shift main switch
- ATN 1983D