Lexus ES300 (2002 year). Manual — part 279

D25088

Same terminal as
a male terminal

D20024

WRONG

CORRECT

D01557

WRONG

Z17004

C

Sensor

OPEN

1

2

B

1

2

1

2

1

2

A

Fig. 1

ECU

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2002 LEXUS ES300 REPAIR MANUAL (RM911U)

(3)

Checking of the contact pressure of the terminal:
Prepare the same terminal as a male terminal.
By inserting it to a female terminal, check the en-
gaged condition and sliding load.

(d)

REPAIR METHOD OF CONNECTOR TERMINAL
(1)

In case that there is any soil at the contact point,
clean the contact point using an air gun or shop rag.
At this time, never polish the contact point using a
sand paper as the platings may come off.

(2)

In case of abnormal contact pressure, replace the
female terminal. At this time, if a male terminal is
gold-plated (gold color), use gold-plated female
terminals and if it is silver-plated (silver color), use
silver-plated female terminals.

(e)

HANDLING OF WIRE HARNESS
(1)

In case of removing the wire harness, check the wir-
ing and clamping condition before the work so as to
restore it correctly.

(2)

Never twist, pull or slack off the wire harness more
than necessary.

(3)

Never make the wire harness come into contact
with a high-temperature part, rotating, moving, vi-
brating or acute-angled part (edge of the panel, tip
of the screw, etc.).

(4)

When installing parts, never sandwich the wire har-
ness between them.

(5)

Never cut or break the cover of the wire harness. If
it is cut or broken, replace it or securely repair it with
a vinyl tape.

2.

CHECK OPEN CIRCUIT

(a)

For the open circuit in the wire harness in Fig. 1, perform
”(b) Check the continuity” or ”(c) Check the voltage” to lo-
cate the section.

Z17005

Fig. 2

Sensor

C

B

A

ECU

1

2

1

2

2

1

B04722

Fig. 3

Sensor

B2

A

1

2

1

2

2

1

C

B1

1

2

ECU

Z17007

Fig. 4

Sensor

C

B

A

1

2

1

2

2

1

5V

5V

0V

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

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2002 LEXUS ES300 REPAIR MANUAL (RM911U)

(b)

Check the continuity.
(1)

Disconnect the connectors ”A” and ”C” and mea-
sure the resistance between them.

Resistance: 1

Ω

or less

HINT:
Measure the resistance while lightly shaking the wire harness
vertically and horizontally.

In the case of Fig. 2:
Between terminal 1 of connector ”A” and terminal 1
of connector ”C”

→

No continuity (open)

Between terminal 2 of connector ”A” and terminal 2
of connector ”C”

→

Continuity

Therefore, it is found out that there is an open circuit
between terminal 1 of connector ”A” and terminal 1
of connector ”C”.

(2)

Disconnect the connector ”B” and measure the re-
sistance between the connectors.
In the case of Fig. 3:
Between terminal 1 of connector ”A” and terminal 1
of connector ”B1”

→

Continuity

Between terminal 1 of connector ”B2” and terminal
1 of connector ”C”

→

No continuity (open)

Therefore, it is found out that there is an open circuit
between terminal 1 of connector ”B2” and terminal
1 of connector ”C”.

(c)

Check the voltage.
(1)

In a circuit in which voltage is applied (to the ECU
connector terminal), an open circuit can be checked
by conducting a voltage check.
As shown in Fig. 4, with each connector still con-
nected, measure the voltage between the body
ground and terminal 1 of connector ”A” at the ECU
5V output terminal, terminal 1 of connector ”B”, and
terminal 1 of connector ”C”, in that order.

(2)

If the results are:
5 V: Between terminal 1 of connector ”A” and body
ground
5 V: Between terminal 1 of connector ”B” and body
ground
0 V: Between terminal 1 of connector ”C” and body
ground
Then it is found out that there is an open circuit in
the wire harness between terminal 1 of ”B” and ter-
minal 1 of ”C”.

Z17008

C

SHORT

1

2

B
1

2

1

2

A

Fig. 5

Z17009

Fig. 6

Sensor

C

B

A

ECU

1

2

1

2

2

1

Z17808

Fig. 7

Sensor

B2

A

1

1

1

C

B1

1

ECU

2

2

2

2

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

34

2002 LEXUS ES300 REPAIR MANUAL (RM911U)

3.

CHECK SHORT CIRCUIT

(a)

If the wire harness is ground shorted as in Fig. 5, locate
the section by conducting a ”continuity check with the
body ground”.

(b)

Check the continuity with the body ground.
(1)

Disconnect connectors ”A” and ”C” and measure
the resistance between terminal 1 and 2 of connec-
tor ”A” and the body ground.

Resistance: 1 M

Ω

or higher

HINT:
Measure the resistance while lightly shaking the wire harness
vertically and horizontally.

In the case of Fig. 6:
Between terminal 1 of connector ”A” and body
ground

→

Continuity (short)

Between terminal 2 of connector ”A” and body
ground

→

No continuity

Therefore, it is found out that there is a short circuit
between terminal 1 of connector ”A” and terminal 1
of connector ”C”.

(2)

Disconnect connector ”B” and measure the resis-
tance between terminal 1 of connector ”A” and body
the ground, and terminal 1 of connector ”B2” and
the body ground.
In the case of Fig. 7:
Between terminal 1 of connector ”A” and body
ground

→

No continuity

Between terminal 1 of connector ”B2” and body
ground

→

Continuity (short)

Therefore, it is found out that there is a short circuit
between terminal 1 of connector ”B2” and terminal
1 of connector ”C”.

IN0383

Example

Ground

IN0384

Ground

ECU Side

W/H Side

Ground

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HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

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2002 LEXUS ES300 REPAIR MANUAL (RM911U)

4.

CHECK AND REPLACE ECU

NOTICE:

Start an inspection of the connector from the back-
side of the connector at the wire harness side with the
connector connected to the ECU.

When no measuring condition is specified, perform
the inspection with the engine stopped and also the
ignition switched ON.

(a)

First check the ECU ground circuit. If it is faulty, repair it.
If it is normal, the ECU could be faulty. So, replace the
ECU with a normal functioning one and check if the symp-
toms appear.

(1)

Measure the resistance between the ECU ground
terminal and body ground.

Resistance: 1

Ω

or less

(2)

Disconnect the ECU connector, check the ground
terminals on the ECU side and wire harness side for
bend and check the contact pressure.