Toyota Sequoia (2005). Manual - part 8

V07268

VIBRATION METHOD: When vibration seems to be the major cause.

CONNECTORS

WIRE HARNESS

PARTS AND SENSOR

Slightly shake the connector vertically and horizontally.

Slightly shake the wire harness vertically and horizontally.
The connector joint, fulcrum of the vibration, and body
through portion are the major areas to be checked thorough-
ly.

Apply slight vibration with a finger to the part of the sensor
considered to be the problem cause and check that the mal-
function occurs.

Shake Slightly

Swing Slightly

Vibrate Slightly

HINT:
Applying strong vibration to relays may result in open relays.

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

IN–29

SYMPTOM SIMULATION

The most difficult case in troubleshooting is when there are no problem symptoms occurring. In such cases,
a thorough customer problem analysis must be carried out, then simulate the same or similar conditions and
environment in which the problem occurred in the customer’s vehicle. No matter how much experience a
technician has, or how skilled he may be, if he proceeds to troubleshoot without confirming the problem
symptoms he will tend to overlook something important in the repair operation and make a wrong guess
somewhere, which will only lead to a standstill. For example, for a problem which only occurs when the en-
gine is cold, or for a problem which occurs due to vibration caused by the road during driving, etc., the prob-
lem can never be determined so long as the symptoms are confirmed with the engine hot or the vehicle at
a standstill. Since vibration, heat or water penetration (moisture) is likely cause for problem which is difficult
to reproduce, the symptom simulation tests introduced here are effective measures in that the external
causes are applied to the vehicle in a stopped condition.
Important Points in the Symptom Simulation Test:
In the symptom simulation test, the problem symptoms should be confirmed, but the problem area or parts
must also be found out. To do this, narrow down the possible problem circuits according to the symptoms
before starting this test and connect a tester beforehand. After that, carry out the symptom simulation test,
judging whether the circuit being tested is defective or normal and also confirming the problem symptoms
at the same time. Refer to the problem symptoms table for each system to narrow down the possible causes
of the symptom.

B02389

B02390

HEAT METHOD: When the problem seems to occur when the suspect area is heated.

NOTICE:

WATER SPRINKLING METHOD:

(1)

(2)

OTHER: When a malfunction seems to occur when electrical load is excessive.

When the malfunction seems to occur on a rainy day or in a
high–humidity condition.

Heat the component that is the likely cause of the malfunction
with a hair dryer or similar object. Check to see if the malfunction
occurs.

Sprinkle water onto the vehicle and check to see if the malfunc-
tion occurs.

Turn on all electrical loads including the heater blower, head
lights, rear window defogger, etc. and check to see if the mal-
function occurs.

HINT:
If a vehicle is subject to water leakage, the leaked water may
contaminate the ECU. When testing a vehicle with a water leak-
age problem, special caution must be taken.

M a l f u n c-

tion

Do not heat to more than 60

C (140

F). (Temperature

is limited not to damage the components.)
Do not apply heat directly to parts in the ECU.

(1)

(2)

Never sprinkle water directly into the engine compart-
ment, but indirectly change the temperature and hu-
midity by applying water spray onto the radiator front
surface.
Never apply water directly onto the electronic compo-
nents.

NOTICE:

IN–30

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

DTC No.

Indicates the diagnostic trouble code.

Page or Instructions

Indicates the page where the inspection procedure
for each circuit is to be found, or gives instructions
for checking and repairs.

Detection Item

Indicates the system of the problem or
contents of the problem.

Trouble Area

Indicates the suspect area of the
problem.

Mass Air Flow Circuit Malfunction

Detection Item

Open or short in mass air flow meter circuit

Mass air flow meter

ECM

DTC No.

(See page)

Trouble Area

MIL*

Memory

P0100

(DI–24)

P0101

(DI–28)

P0115

(DI–33)

Open or short in intake air temp. sensor

circuit

Intake air temp. sensor

ECM

Intake Air Temp. Circuit

Malfunction

P0110

(DI–29)

Open or short in engine coolant temp. sensor circuit

Engine coolant temp. sensor

ECM

Throttle/ Pedal Position Sensor/Switch

”A” Circuit Malfunction

Engine Coolant Temp.

Circuit Malfunction

Open or short in throttle position sensor circuit

Throttle position sensor

ECM

DTC CHART (SAE Controlled)

HINT:
Parameters listed in the chart may not be exactly the same as your reading due to the type of instrument or other
factors.

If a malfunction code is displayed during the DTC check mode, check the circuit for that code listed in the table
below. For details of each code, turn to the page referred to under the ”See page” for the respective ”DTC No.”
in the DTC chart.

Mass Air Flow Circuit

Range/ Performance Problem

Mass air flow meter

Throttle position sensor

Throttle/ Pedal Position Sensor/ Switch

”A” Circuit Range / Performance Prob-

lem

P0116

(DI–37)

Engine Coolant Temp.

Circuit Range/ Performance Problem

Engine coolant temp. sensor

Cooling system

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

IN–31

DIAGNOSTIC TROUBLE CODE CHART

The inspection procedure is shown in the table below. This table permits efficient and accurate troubleshoot-
ing using the diagnostic trouble codes displayed in the diagnostic trouble code check. Proceed with trouble-
shooting in accordance with the inspection procedure given in the diagnostic chart corresponding to the
diagnostic trouble codes displayed. The engine diagnostic trouble code chart is shown below as an example.

IN–32

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

PROBLEM SYMPTOMS TABLE

The suspected circuits or parts for each problem symptom are shown in the table below. Use this table to
troubleshoot the problem when a ”Normal” code is displayed in the diagnostic trouble code check but the
problem 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

DI–147

DI–151

IN–29

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–88

DI–144

DI–151

EM–3

DI–151

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.

ST–2
ST–17

DI–144

DI–151

DI–144

DI–151

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