Lexus ES300 (1997 year). Manual - part 490

IN–24

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED 
SYSTEMS

24

1997 LEXUS ES300   (RM511U)

5.

PROBLEM SYMPTOMS TABLE

The suspect circuits or parts for each problem symptom are shown in the table below. Use this table to trou-
bleshoot the problem when a ”Normal” code is displayed in the diagnostic trouble code check but the prob-
lem is still occurring. Numbers in the table indicate the inspection order in which the circuits or parts should
be checked.
HINT:
When the problem is not detected by the diagnostic system even though the problem symptom is present,
it is considered that the problem is occurring outside the detection range of the diagnostic system, or that
the problem is occurring in a system other than the diagnostic system.

Symptom

Suspect Area

See page

Engine does not crank (Does not start)

No initial combustion (Does not start)

No complete combustion (Does not start)

1. Starter and starter relay

1. ECM power source circuit

2. Fuel pump control circuit

3. Engine control module (ECM)

1. Starter signal circuit

2. Fuel pump control circuit

1. Fuel pump control circuit

ST–12,13

DI–124

DI–127

IN–30

PROBLEM SYMPTOMS TABLE

1. Compression

2. Fuel pump control circuit

1. A/C signal circuit

2. Fuel pump control circuit

1. A/C signal circuit (Compressor circuit)

2. ECM power source circuit

1. Starter signal circuit

2. Fuel pump control circuit

1. Starter signal circuit

2. Fuel pump control circuit

3. Compression

idling)

High engine idle speed (Poor idling)

Hot engine

Cold engine (Difficult to start)

Engine cranks normally (Difficult to start)

AC–54

DI–124

DI–121

DI–127

DI–121

DI–127

EM–3

DI–127

DI–121

DI–127

 Problem Symptom

 Page 

   Indicates the page where the flow chart for each circuit 
   is located.

 Circuit Inspection, Inspection Order

   Indicates the circuit which needs to be checked for each problem 
   symptom. Check in the order indicated by the numbers.

 Circuit or Part Name

   Indicates the circuit or part which needs to be checked.

V08423

Knock Sensor 1

GR

ECM

KNK

E1

12
E6

WIRING DIAGRAM

 Wiring Diagram

   This shows a wiring diagram of the circuit.
  Use this diagram together with ELECTRICAL
   WIRING DIAGRAM to thoroughly understand the
    circuit. 
   Wire colors are indicated by an alphabetical code.
    B = Black, L = Blue, R = Red, BR = Brown, 
    LG = Light Green, V = Violet, G = Green, 
    O = Orange, W = White, GR = Gray, P = Pink, 
    Y = Yellow 
   The first letter indicates the basic wire color and
   the second letter indicates the color of the stripe.

DTC

P0325

Knock Sensor 1 Circuit Malfunction

CIRCUIT DESCRIPTION

Knock sensor is fitted to the cylinder block to detect engine knocking. This sensor contains a piezoelectric element which

generates a voltage when it becomes deformed, which occurs when the cylinder block vibrates due to knocking. If engine

knocking  occurs, ignition timing is retarded to suppress it.

DTC No.

DTC Detecting Condition

Trouble Area

P0325

No knock sensor 1 signal to ECM with engine speed, 

1,200 rpm or more.

 Open or short in knock sensor1 circuit

 Knock sensor 1 (looseness)

 ECM

If the ECM detects the above diagnosis conditions, it operates the fall safe function in which the corrective retard angle

value is set to the maximum value.

 Diagnostic Trouble Code No. and Detection Item

 Circuit Description

   The major role and operation, etc. of the circuit 
   and its component parts are explained.

 Indicates the diagnostic trouble code, diagnostic 

   trouble code set parameter and suspect area of 
   the problem.

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED 
SYSTEMS

IN–25

25

1997 LEXUS ES300   (RM511U)

6.

CIRCUIT INSPECTION

How to read and use each page is shown below.

V08425

LOCK

KNK

E6 Connector

(a) Remove the glove compartment (See page SF–37).
(b) Disconnect the E6 connector of ECM.

INSPECTION PROCEDURE

Replace knock sensor.

1

Check continuity between terminal KNK of ECM connector and body ground.

OK:

Check knock sensor (See page SF–34).

Measure resistance between terminal KNK of ECM connector 
and body ground.

Resistance: 1 M

Ω

 or higher

Connector being checked is connected.

 Indicates the condition of the connector of ECU during the check.

PREPARATION:

CHECK:

2

Go to step 3.

OK

OK

NG

 Indicates the position of the ignition switch during the check.

Check from the connector back side.
(with harness)

Ignition Switch LOCK (OFF)

Ignition Switch START

LOCK

Ignition Switch ON

Ignition Switch ACC

START

ON

ACC

 Inspection Procedure

  Use the inspection procedure to determine
  if the circuit is normal or abnormal, and if
 it is abnormal, use it to determine whether
  the problem is located in the sensors, 
  actuators, wire harness or ECU.

 Indicates the place to check the voltage or resistance.

 Indicates the connector position to be checked, from the front or back side.

Connector being checked is disconnected.

Check from the connector front side. (without harness)
In this case, care must be taken not to bend the terminals.

E6 Connector

KNK

Wire Harness

E6 Connector

KNK

A00255

AB0117
A00265

IN–26

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED 
SYSTEMS

26

1997 LEXUS ES300   (RM511U)

IN028–02

FI0046

FI0047

FI0048

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED 
SYSTEMS

IN–27

27

1997 LEXUS ES300   (RM511U)

HOW TO USE THE DIAGNOSTIC
CHART AND INSPECTION
PROCEDURE

1.

CONNECTOR CONNECTION AND TERMINAL IN-
SPECTION

For troubleshooting, diagnostic trouble code charts or
problem symptom charts are provided for each circuit with
detailed inspection procedures on the following pages.

When all the component parts, wire harnesses and con-
nectors of each circuit except the ECU are found to be
normal in troubleshooting, then it is determined that the
problem is in the ECU. Accordingly, if diagnosis is per-
formed without the problem symptoms occurring, refer to
step 8 to replace the ECU, even if the problem is not in the
ECU. So always confirm that the problem symptoms are
occurring, or proceed with inspection while using the
symptom simulation method.

The instructions ”Check wire harness and connector” and
”Check and replace ECU” which appear in the inspection
procedure, are common and applicable to all diagnostic
trouble codes. Follow the procedure outlined below
whenever these instructions appear.

OPEN CIRCUIT:
This could be due to a disconnected wire harness, faulty con-
tact in the connector, and a connector terminal pulled out, etc.
HINT:

It is rarely the case that a wire is broken in the middle of
it. Most cases occur at the connector. In particular, care-
fully check the connectors of sensors and actuators.

Faulty contact could be due to rusting of the connector
terminals, to foreign materials entering terminals or a de-
formation of connector terminals. Simply disconnecting
and reconnecting the connectors once changes the
condition of the connection and may result in a return to
normal operation. Therefore, in troubleshooting, if no ab-
normality is found in the wire harness and connector
check, but the problem disappears after the check, then
the cause is considered to be in the wire harness or con-
nectors.

SHORT CIRCUIT:
This could be due to a contact between wire harness and the
body ground or to a short circuit occurred inside the switch etc.
HINT:
When there is a short between the wire harness and body
ground, check thoroughly whether the wire harness is caught
in the body or is clamped properly.