Lexus SC300 / Lexus SC400. Manual - part 914

OK

NG

INSPECTION PROCEDURE

1

Check engine speed sensor, No. 1, No. 2 cam position sensor

C

OK

P

For engine speed sensor.

(2) Remove engine under cover.

(2) Disconnected engine speed sensor connector.

For No.1, No. 2 cam position sensor,

(2) Disconnect No. 1, No. 2 cam poisition sensor con-

nectors.

Measure resistance of engine speed sencor, No. 1 and
No. 2 cam position sensor.

Replace engine speed sensor, No. 1, No. 2 cam poistion
sensor.

TR–50

–

ENGINE TROUBLESHOOTING

Circuit Inspection

OK

NG

OK

NG

2

Check for open and short in harness and connector between engine & ECT ECU and each sen-
sor (See page 

IN–27

).

Repair or replace harness or connector.

3

Inspect sensor installation and teeth of signal plate.

Tighen the sensor.
Replace signal plate.

Check and replace engine and ECT ECU.

–

ENGINE TROUBLESHOOTING

Circuit Inspection

TR–51

Diag. Code 13

RPM Signal Circuit (No. 2)

CIRCUIT DESCRIPTION

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

TR–46

.

Code No.

Diagnostic Code Detecting Condition

Trouble Area

13

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

Open or short in NE circuit

Distributor

13

No 12 pulses of NE to ECU during the interval

Distributor

ECU

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

ECU

DIAGNOSTIC CHART

This code indicates that a momentary interruption of the RPM signal from the distributor to the ECU has
occurred, but that it is returned to normal. Note that although this problem may not necessarily appear
at the time of inspection, it cannot be ignored because this diagnostic code is output, indicating that there
is or was a malfunction in the RPM signal circuit; this ”malfunction” is usually a loose connector.
The distributor connector and the NE terminal of the ECU connector must therefore be checked for the
following:

1. Loose 

connectors

2. 

Dirty connector terminals

3. 

Loose connector terminals

TR–50

–

ENGINE TROUBLESHOOTING

Circuit Inspection

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