Toyota Sequoia (2005). Manual — part 7

Important Points in the Customer Problem Analysis

What ––––– Vehicle model, system name

When ––––– Date, time, occurrence frequency

Where ––––– Road conditions

Under what conditions? ––––– Running conditions, driving conditions, weather conditions

How did it happen? ––––– Problem symptoms

(Sample) Engine control system check sheet.

ENGINE CONTROL SYSTEM Check Sheet

Customer’s Name

Driver’s Name

Data Vehicle
Brought in

License No.

Model and Model
Year

Frame No.

Engine Model

Odometer Reading

km
miles

Problem Symptoms

Engine does
not Start

Difficult to
Start

Poor Idling

Poor
Drive ability

Engine Stall

Others

Engine does not crank

No initial combustion

No complete combustion

Engine cranks slowly

Other

Incorrect first idle

Idling rpm is abnormal

High ( rpm)

Low ( rpm)

Rough idling

Other

Hesitation

Back fire

Muffler explosion (after–fire)

Surging

Knocking

Other

Soon after starting

After accelerator pedal depressed

After accelerator pedal released

During A/C operation

Shifting from N to D

Other

Data Problem

Constant

Sometimes ( times per day/month)

Inspector’s
Name

CUSTOMER PROBLEM ANALYSIS CHECK

–

INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

IN–25

25

1.

CUSTOMER PROBLEM ANALYSIS

In troubleshooting, the problem symptoms must be confirmed accurately and all preconceptions must be
cleared away in order to give an accurate judgment. To ascertain just what the problem symptoms are, it is
extremely important to ask the customer about the problem and the conditions at the time it occurred.
Important Point in the Problem Analysis:
The following 5 items are important points in the problem analysis. Past problems which are thought to be
unrelated and the repair history, etc. may also help in some cases, so as much information as possible should
be gathered and its relationship with the problem symptoms should be correctly ascertained for reference
in troubleshooting. A customer problem analysis table is provided in Diagnostics section for each system
for your use.

IN–26

–

INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

26

2.

SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK

The diagnostic system in the SEQUOIA fulfills various functions. The first function is the Diagnostic Trouble
Code Check in which a malfunction in the signal circuits to the ECU is stored in code in the ECU memory
at the time of occurrence, to be output by the technician during troubleshooting. Another function is the Input
Signal Check which checks if the signals from various switches are sent to the ECU correctly.
By using these check functions, the problem areas can be narrowed down quickly and troubleshooting can
be performed effectively. Diagnostic functions are incorporated in the following systems in the SEQUOIA.

System

Diagnostic Trouble

Code Check

Input Signal Check

(Sensor Check)

Diagnostic Test

Mode (Active Test)

1. Engine

(with Check

Mode)

2. Automatic Transmission

(with Check

Mode)

3. Air Suspension Control System

(with Check

Mode)

4. Tire Pressure Warning System

5. ABS with EBD & BA & TRAC & VSC System

6. Can Communication System

7. Supplemental Restraint System

(with Check

Mode)

8. Power Seat Control System

w/ Driving Position Memory

9. Cruise Control System

10.Engine Immobilizer System

11.Combination Meter System

12.Sliding Roof System

13.Body Control System

14.Driver Door Control System

15.Passenger Door Control System

16.Back Door Control System

17.Multiplex Communication System

18.Audio System

19.Rear Seat Audio System

20.Rear Seat Entertainment System

21.Air Conditioning System

In diagnostic trouble code check, it is very important to determine whether the problem indicated by the diag-
nostic trouble code is still occurring or occurred in the past but returned to normal at present. In addition,
it must be checked in the problem symptom check whether the malfunction indicated by the diagnostic
trouble code is directly related to the problem symptom or not. For this reason, the diagnostic trouble codes
should be checked before and after the symptom confirmation to determine the current conditions, as shown
in the table on the next page. If this is not done, it may, depending on the case, result in unnecessary trouble-
shooting for normally operating systems, thus making it more difficult to locate the problem, or in repairs not
pertinent to the problem. Therefore, always follow the procedure in correct order and perform the diagnostic
trouble code check.

DIAGNOSTIC TROUBLE CODE CHECK PROCEDURE

Diagnostic Trouble
Code Check (Make a
note of and then clear)

Confirmation
of Symptoms

Diagnostic Trouble
Code Check

Problem Condition

Diagnostic Trouble
Code Display

Problem symptoms
exist

Same diagnostic
trouble code is
displayed

Problem is still occurring in the diagnostic
circuit

Normal code is
displayed

The problem is still occurring in a place
other than in the diagnostic circuit
(The diagnostic trouble code displayed
first is either for a past problem or it is a
secondary problem)

No problem
symptoms exist

The problem occurred in the diagnostic
circuit in the past

Normal Code Display

Problem symptoms
exist

Normal code is
displayed

The problem is still occurring in a place
other than in the diagnostic circuit

No problem
symptoms exist

Normal code is
displayed

The problem occurred in a place other
than in the diagnostic circuit in the past

–

INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

IN–27

27

Diagnostic trouble code check

Making a note of and clearing of the diagnostic trouble codes displayed

Symptom confirmation

No problem symptoms
exist

Problem symptoms
exist

Simulation test using the symptom
simulation methods

Normal code displayed

Problem symptoms exist

Normal code displayed

No problem symptoms exist

Diagnostic trouble code check

Troubleshooting of problem indicated
by diagnostic trouble code

Diagnostic trouble code displayed

Problem symptoms exist

System Normal

Troubleshooting of each
problem symptom

If a diagnostic trouble code was
displayed in the initial diagnostic
trouble code check, it indicates
that the trouble may have occurred
in a wire harness or connector in
that circuit in the past. Therefore,
check the wire harness and con-
nectors (See page

IN–35

).

IN–28

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INTRODUCTION

HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS

28

Taking into account the above points, a flow chart showing how to proceed with troubleshooting using the
diagnostic trouble code check is shown below. This flow chart shows how to utilize the diagnostic trouble
code check effectively, then by carefully checking the results, indicates how to proceed either to diagnostic
trouble code troubleshooting or to troubleshooting of problem symptoms table.