Lexus SC300 / Lexus SC400. Service manual — part 666

Diag. Code 13

RPM Signal Circuit (No.2)

CIRCUIT DESCRIPTION

Refer to RPM signal circuit (No. 1) on page

TR–48

.

Code No.

Diagnostic Code Detecting Condition

Trouble Area

No NE signal to ECU for 0.1 sec. or more at
1,000 rpm or more.

•

Open or short in engine speed sensor

•

circuit.

•

Engine speed sensor

•

ECU

13

No 12 pulses of NE to ECU during the interval
between G1 and G2 pulses.

•

Open or short in engine speed sensor

•

circuit.

•

Mechanical system malfunction (skipping
teeth of timing belt, belt stretched)

•

Engine speed sensor

•

ECU

Deviation in G (G1, G2) and NE signal contin-
ues for 1 sec. during idling (throttle fully
closed) after engine warmed up.

•

Mechanical system malfunction (skipping
teeth of timing belt, belt stretched)

•

No. 1, No. 2 cam position sensor

•

ECU

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Inspect sensor installation. Check if any teeth of NE
signal plate are broken

Check valve timing (Check for loose and jumping teeth

of timing belt (See page

EM–51

)).

Tighten the sensor.
Replace signal plate.

Adjust valve timing
(Repair or replace timing belt).

HINT: Perform troubleshooting of diag. code 12 first. If no trouble is found, troubleshoot the

following mechanical systems.

Check for momentary interruption

(See page

TR–23

).

TR–52

–

ENGINE TROUBLESHOOTING

Circuit Inspection

MEMO –

ENGINE TROUBLESHOOTING

TR–53

Diag. Code 14, 15

Ignition Signal Circuit

CIRCUIT DESCRIPTION

The ECU determines the ignition timing, turns on Tr1 at a predetermined angle (

°

CA) before the desired

ignition timing and outputs an ignition signal (IGT) ”1” 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 Tr2 turns on.
When it reaches the ignition timing, the ECU turns Tr1 off and outputs the IGT signal ”O”.
This turns Tr2 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 ECU.
The ECU stops fuel injection as a fail safe function when the IGF signal is not input to the ECU.

Code No.

Diagnostic Code Detecting Condition

Trouble Area

14

No IGF1 signal to ECU for 8–11 consecutive
IGT1 signal.

•

Open or short in IGF1 and IGT1 circuit from
No. 1 igniter – ECU.

•

No. 1 igniter

•

ECU

15

No IGF2 signal to ECU for 8–11 consecutive
IGT2 signal.

•

Open or short in IGF2 and IGT2 circuit from
No. 2 igniter – ECU.

•

No. 2 igniter

•

ECU

HINT: No. 1 igniter is for left bank and No. 2 igniter is for right bank.

WIRING DIAGRAM

TR–54

–

ENGINE TROUBLESHOOTING

Circuit Inspection

DIAGNOSTIC CHART

DIAGNOSTIC CHART

Refer to inspection procedure in details.
HINT: If diag. code 14 is displayed, check No. 1 igniter circuit.

If diag. code 15 is displayed, check No. 2 igniter circuit.

Check for spark.

Check for open and short in IGF signal circuit
between igniter and ECU.

Check voltage of terminal IGF.

Check and replace ECU.

Check voltage of terminal IGT.

Check voltage of igniter power source.

Check for open and short in primary coil circuit.

Check ignition coil.

Replace igniter.

Check and repair igniter power source circuit.

Check voltage of terminal IGT
(Disconnect igniter connector).

Check and repair igniter power source circuit.

Repair or replace harness or
connector.

Replace igniter.

Repair or replace harness or
connector

Replace ignition relay.

Replace ignition relay.

Check for open and short in IGT signal circuit
between igniter and ECU.

Check and replace ECU.

Repair or replace harness or
connector

Replace igniter.

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–55