Lexus SC300 / Lexus SC400. Manual - part 849

FAIL–SAFE CHART

If any of the following codes is recorded, the ECU enters fail–
safe mode.

Code No.

Fail–Safe Operation

Fail–Safe Deactivation Conditions

14

Fuel cut

1 IGF1 detected in consecutive 8 ignitions.

15

Fuel cut

1 IGF2 detected in consecutive 8 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 controlled between 10

°

 ~ 30

°

BTDC,
Injection time controlled between 3 msec. ~ 30 m
sec., in relation to:

•

Engine rpm

•

Throttle angle

•

ISC step value

KS input 15 times/sec. or more.

35

Atmospheric pressure is fixed at 760 mmHg.

Returned to normal condition.

The following 1 or 2 must be repeated at least 2

times consecutively.

41

VTA1 is fixed at 0

°

1

When IDL is ON

41

VTA1 is fixed at 0

°

1

When IDL is ON
0.25 V 

 VTA1 

 0.95 V

2

When IDL is OFF

2

When IDL is OFF
0.25 V 

 VTA1 

 4.9 V

The following 1 or 2 must be repeated at least 2

times consecutively.

47

Value of VTA1 is used

1

When IDL2 is ON

47

Value of VTA1 is used.

1

When IDL2 is ON
0.25 V 

 VTA2 

 0.95 V

2

When IDL2 is OFF

2

When IDL2 is OFF
0.25 V 

 VTA2 

 4.9 V

52

Max. timeing retardation.

IG switch OFF.

53

Max. timeing retardation.

Returned to normal condition.

55

Max. timeing retardation.

IG switch OFF.

Back–Up Function
If there is trouble with the program in the ECU and the ignition signals (IGT) are not output, the ECU 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 satrting signal (STA) and the throttle position signal
(IDL). Also, the ignition timing is fixed at the initial ignition timing, 5

°

 BTDC, without relation to the engine speed.

HINT: If the engine is controlled by the back–up function, the CHECK ENGINE light lights up to warn the driver
of the malfunction but the diagnostic code is not output.

TR–22

–

ENGINE TROUBLESHOOTING

Fail–Safe Chart

CHECK FOR MOMENTARY
INTERRUPTION

As described in the preceding paragraph, abnormality detection
ability in the test mode is increased compared to that in the normal
mode, so that when momentary interruptions or momentary shorts
occur in the ECU signal circuits (G1, G2, NE, THW, THA, VTA1,
VTA2) shown in the table below, the appropriate diagnostic code
is output.
Accordingly, when the diagnostic codes shown in the table below
(13, 22, 24, 41, 47) are output during the diagnostic code check,
and inspection of the appropriate circuits reveals no abnormality,
perform the check for momentary interruption as described below.
By performing the check for momentary interruption, the place
where momentary interruptions or momentary shorts are occur-
ring due to poor contacts can be isolated.

CLEAR DIAGNOSTIC CODES

See page 

TR–13

.

SET TEST MODE

1. 

With the ignition switch off, using SST, connect the terminals
TE2 and E1 of the TDCL.
SST 09843–18020

2.  Start the engine and check to see the ”CHECK” engine

warning light to go off.

PERFORM A SIMULATION TEST

Using the symptom simulation (See page 

IN–20

), apply vibration

to and pull lightly on the wire harness, connector or terminals in the
circuit indicated by the malfunction code.
In this test, if the ”CHECK” engine warning light lights up, it indi-
cates that the place where the wire harness, connector or termi-
nals being pulled or vibrated has faulty contact. Check that point
for loose connections, dirt on the terminals, poor fit or other prob-
lems and repair as necessary.
HINT: After cancelling out the diagnostic code in memory and set
the test mode, if the ”CHECK” engine warning light does not go off
after the engine is started, check thoroughly for faulty contact,
etc., then try the check again. If the ”CHECK” engine warning light
still does not go off, check and replace ECU.

–

ENGINE TROUBLESHOOTING

Check for Momentary Interruption

TR–23

YES

NO

NO

YES

YES

NO

OK

NG

BASIC INSPECTION

When the normal code is displayed in the diagnostic code check, troubleshooting should be performed in the
order for all possible circuits to be considered as the causes of the problems.
In many cases, by carrying out the basic engine check shown in the following flow chart, the location causing
the problem can be found quickly and efficiently. Therefore, use of this check is essential in engine troubleshoot-
ing.

1

Is battery voltage 11 V or more when engine is stopped?

Charge or replace battery.

2

Is engine cracnked?

Proceed to matrix to matrix chart of problem
symptoms on page 

TR–35

.

3

Does engine start?

Go to step [7]

4

Check air filter

C

Hint

P

Remove air filter

Visially check that the air cleaner element is not exces-
sively damaged or oily.

If necessary, clean element with compressed air.  First
blow from inside thoroughly, then blow off outside of ele-
ment.

Repair or replace

Go to Step [5].

TR–24

–

ENGINE TROUBLESHOOTING

Basic Inspection

OK

NG

OK

NG

5

Check idle speed.

C

OK

P

(1) Warm up engine at normal operating temperature.

(2) Switched off all accessories.

(3) Switched off air conditioner.

(4) Shift transmission into “N” range.

(5) Connect tachometer test probe to terminal IG 

 of

check connector, and set the tachometer to the
4–cylinder range.

Check idle speed.

Idle speed: 650 ~ 750 rpm

Caution:

NEVER allow tachometer test probe to touch
ground as it could result in damage to igniter
and/or coil.

As some tachometers are not compatible with
this ignition system, we recommended that you
confirm compatibility of your unit before use.

Proceed to matrix chart of problem symptoms on page

TR–35

.

6

Check ignition timing.

C

OK

P

(1) Warm up engine at normal operating temperture.

(2) Shift transmission into “N” range.

(3) Keep the engine speed at idle.

(4) Using SST, connect terminals TE1 and E1 of check

connector.

SST 09843–18020

(5) Using a timing light. connect the tester to No. 6

high–tension cord.

Check ignition timing.

Ignition Timing: 8–12



 BTDC at idle

Proceed to page 

IG–28

 and continue to troubleshoot.

Proceed to matix chart of problem symptoms on

page 

TR–35

.

–

ENGINE TROUBLESHOOTING

Basic Inspection

TR–25