1986 TOYOTA SUPRA turn signal

CIRCUIT DESCRIPTION
The IAC valve is situated on the intake air chamber In-
take air bypassing the throttle valve is directed to the
IAC valve through a passage.
A step motor is built into the IAC valve. It consists of 4
coils, a magnetic rotor, valve shaft and a valve.
When the current flows to the coils due to signals from
the ECM, the rotor turns and moves the valve shaft for-
ward or backward, changing the clearance between
the valve and the valve seat.
In this way the intake air volume bypassing the throttle
valve is regulated, controlling the engine speed.
There are 125 possible positions to which the valve can
be opened.

With the engine idling measure wave forms
between terminals ISC1, ISC2, ISC3,
ISC4 and E01 of engine control module
when A/C switch ON or OFF.
HINT:
The correct waveforms are as shown.
INSPECTION USING OSCILLOSCOPEReference
IAC Valve Circuit
EG±586± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

Diagnosis Inspection (Test Mode)
Compared to the normal mode, the test mode has an in-
creased sensing ability to detect malfunctions.
It can also detect malfunctions in the starter signal circuit, the
IDL contact signal of the throttle position sensor, air condi-
tioning signal and park/neutral position switch signal.
Furthermore, the same diagnostic items which are detected
in the normal mode can also be detected in the test mode.
DIAGNOSTIC TROUBLE CODE CHECK
1. Initial conditions.
(a) Battery voltage 11 V or more
(b) Throttle valve fully closed
(c) Transmission in neutral position
(d) Air conditioning switched OFF
2. Turn ignition switch OFF
3. Using SST, connect terminals TE2 and E1 of the data link
connector 2.
SST 09843±18020
4. Turn ignition switch ON.
HINT:
wTo confirm that the test mode is operating, check that the
malfunction indicator lamp flashes when the ignition
switch is turned to ON.
wIf the malfunction indicator lamp does not flash, proceed
to troubleshooting of the TE2 terminal circuit on page
EG±484.
5. Start the engine.
6. Simulate the conditions of the malfunction described by the
customer.
7. After the road test, using SST, connect terminals TE1 and E1
of the data link connector 2.
SST 09843±18020
8. Read the diagnostic trouble code on malfunction indicator
lamp on the telltale light RH (See page EG±385).
9. After completing the check, disconnect terminals TE1, TE2
and E1, and turn off the display.
HINT:
wThe test mode will not start if terminals TE2 and E1 are
connected after the ignition switch is turned ON.
wWhen the engine is not cranked, diagnostic trouble
codes º43º (Starter signal) output, but this is not
abnormal.
wWhen the automatic transmission shift lever is in the ºDº,
º2º, ºLº or ºRº shift position, or when the air conditioning
is on or when the accelerator pedal is depressed, code
º51º (Switch condition signal) is output, but this is not
abnormal. EG±386
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

FAIL±SAFE CHART
If any of the following codes is detected, the ECM enters fail±safe mode.
 DTC No. Fail±Safe Operation Fail±Safe Deactivation Conditions
 14 Fuel cut 1 IGF detected in 3 consecutive ignitions
 16 Torque control prohibited Returned to normal condition
 22 THW is fixed at 80°C (176°F) Returned to normal condition 24 THA is fixed at 20°C (68°F) Returned to normal condition 
 
 
 
 
 
31
 
 
 
 
 
 

Ignition timing fixed at 10°BTDC

Injection time fixed:
(Starting....9 msec.
(IDL ON....3.6 msec.
(IDL OFF....6.7 msec.
 
 
 
 
 
 
KS input 15 times/sec. or more
 
 35
 
 
Atmospheric pressure is fixed at 101.3 kPa
(760 mmHg, 29.92 in.Hg) 
 Returned to normal condition
 
 
 
 

41
 
 
 
 

VTA1 is fixed at 0°
 
 
 
 

The following must each be repeated at least 2
Times consecutively:

0.25 V
VTA
0.95 V

IDL: ON 
 52
 
 Max. timing retardation
 
 IG switch OFF
 53 Max. timing retardation Returned to normal condition
 55 Max. timing retardation IG switch OFF
Back±Up Function
If there is trouble with the program in the ECM and the ignition signals (IGT) are not output from the microcomput-
er, the ECM controls fuel injection and ignition timing at predetermined levels as a back±up function to make
it possible to continue to operate the vehicle.
Furthermore, the injection duration is calculated from the starting signal (STA) and the throttle position signal
(IDL). Also, the ignition timing is fixed at the initial ignition timing, 10°BTDC, without relation to the engine speed.
HINT: if the engine is controlled by the back±up function, the malfunction indicator lamp lights up to warn the
driver of the malfunction but the diagnostic trouble code is not output. EG±398
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

DTC 13 G NE Signal Circuit (No.2)
CIRCUIT DESCRIPTION
See G, NE signal circuit (No. 1) on page EG±409.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble Area 
 
13
 
  No NE signal to ECM for 0.1 sec. or more at
1,000 rpm or more 
 
Open or short in NE circuit

Distributor 
 
 
13 
 
 
NE signal does not pulse 12 times to ECM
during the interval between G1 and G2 pulses
 
 
 

Distributor

ECM
DIAGNOSIS
This code indicates that a intermittent problems of the G, NE signal from the distributor to the ECM has occurred,
but that it has returned to normal. Note that although this problem may not necessarily appear at the time of
inspection, it cannot be ignored because this diagnostic trouble code is output, indicating that there is or was
a malfunction in the G, NE signal circuit; this ºmalfunctionº is usually a loose connector.
The distributor connector and the NE terminal of the ECM connector must therefore be checked for the following:
1. Loose connectors
2. Dirty connector terminals
3. Loose connector terminals EG±412
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

DTC 14 Ignition Signal Circuit
CIRCUIT DESCRIPTION
The ECM determines the ignition timing, turns on Tr1 at a predetermined angle (°CA) before the desired ignition
timing and outputs an ignition signal (IGT) º1º to the igniter.
Since the width of the IGT signal is constant, the dwell angle control circuit in the igniter determines the time
the control circuit starts primary current flow to the ignition coil based on the engine rpm and ignition timing one
revolution ago, that is, the time the Tr
2 turns on.
When it reaches the ignition timing, the ECM turns Tr
1 off and outputs the IGT signal ºOº.
This turns Tr
2 off, interrupting the primary current flow and generating a high voltage in the secondary coil which
causes the spark plug to spark. Also, by the counter electromotive force generated when the primary current
is interrupted, the igniter sends an ignition confirmation signal (IGF) to the ECM.
The ECM stops fuel injection as a fail safe function when the IGF signal is not input to the ECM.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble Area 
 
14
 
  No IGF signal to ECM for 6 consecutive IGT
 
 
Open or short in IGF OR IGT circuit from igniter
to ECM
 
 
14 
 
No IGF signal to ECM for 6 consecutive IGT
signals 
 
to ECM

Igniter

ECM
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±413

INSPECTION PROCEDURE
(See page IN±30).
(See page EG±404)
Check for spark.
Disconnect the high±tension cord from the distributor, hold its end about 12.5 mm (1/2º) from
the ground, see if spark occurs while the engine is being cranked.
Spark should be generated.
To prevent excess fuel being injected from the injectors during this check. Don't crank the engine
for more than 1 Ð 2 seconds at a time.
Check for open and short in harness and connector in IGF signal circuit
between engine control module and igniter (see page IN±30).
Disconnect igniter connector and check voltage between terminal IGF
of engine control module connector and body ground.
Repair or replace harness or connector.
Replace igniter.
Check and replace engine control module.
(1) Disconnect igniter connector.
(2) Connect SST (check harness ªAº).
See page EG±404)
SST 09990±01000
(3) Turn ignition switch ON.
Measure voltage between terminal IGF of engine
control module connector and body ground.
Voltage: 4.5 ~ 5.5 V EG±414
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

(See page EG±397).
CIRCUIT DESCRIPTION
The EGR system is designed to recirculate the exhaust gas, controlled according to the driving condi-
tions, back into the intake air±fuel mixture. It helps to slow down combustion in the cylinder and thus
lower the combustion temperature which, in turn, reduces the amount of NOx emission. The amount
of EGR is regulated by the EGR vacuum modulator according to the load.
If even one of the following conditions is fulfilled,
the VSV is turned ON by a signal from the ECM.
This results in atmospheric air acting on the EGR
valve, closing the EGR valve and shutting off the
exhaust gas (EGR cut±OFF).

Engine coolant temp. below 50°C (122°F)

During deceleration (Throttle valve closed)

Light engine load (amount of intake air very
small).

Engine speed over 5,200 rpm

Traction control is operating
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble Area
EGR gas temp. is 70°C (158°F) or less for 1 ~
4 min. under conditions (a) and (b):
(2) trip detection logic)*
(a) Engine coolant temp.: 63°C (145°F) or
more
(b) EGR operation possible (Example A/T in
3rd speed (5th for M/T), A/C ON, 96
km/h (60 mph), Flat road)

Open in EGR gas temp. sensor circuit

Short in VSV circuit for EGR

EGR hose disconnected, valve stuck

Clogged EGR gas passage

ECM
DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
(b) To check that the malfunction is corrected when the repair is completed by confirming that diag±
nostic trouble code is no longer detected.
DTC 71 EGR System Malfunction
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±453

INSPECTION PROCEDURE
(EG±463).
Check output condition of diagnostic trouble code 51.
*: Before the STA signal is input (ST is not ON),
diagnostic trouble code 43 is also output.
Diagnostic trouble code 42 is output with vehicle
speed 5 km/h (3 mph) or below.
Setting the test mode.
(1) Turn ignition switch OFF.
(2) Connect terminals TE2 and E1 of DLC2.
(3) Turn ignition switch ON.
(For checking terminal IDL, disconnect the
vacuum hose from the throttle body, then apply
vacuum to the throttle opener (See page
EG±219)).
(For checking terminal A/C, start the engine.)
(4) Connect terminals TE1 and E1 of DLC1 or
DLC2.
Check if code ª51º is output by the malfunction indi-
cator lamp.
Proceed to next circuit inspection shown on matrix
chart (See page EG±408).
IDL1...Go to step [2].
PNP....Go to page EG±463.
A/C....Go to step [3].
Condition
Throttle Position
Park/Nuetral Posi±
Code
tion Switch (PNP)
P or N position
released
R,D, 2 or L position
Accelerator pedal
Accelerator pedal
depressed
A/C SW ON
A/C SW OFFA/C Switch (A/C)
Sensor (IDL1)
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±461