Lexus ES300 (1997 year). Manual — part 488
IN026–02
IN–16
–
INTRODUCTION
HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
16
1997 LEXUS ES300 (RM511U)
HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
GENERAL INFORMATION
A large number of ECU controlled systems are used in the LEXUS ES300. In general, the ECU controlled
system is considered to be a very intricate system requiring a high level of technical knowledge and expert
skill to troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, troubleshoot-
ing of these systems is not complex. If you have adequate understanding of the system and a basic knowl-
edge of electricity, accurate diagnosis and necessary repair can be performed to locate and fix the problem.
This manual is designed through emphasis of the above standpoint to help service technicians perform ac-
curate and effective troubleshooting, and is compiled for the following major ECU controlled systems:
System
Page
1. Engine
2. Automatic Transaxle
3. Electronic Modulated Suspension
4. Anti–Lock Brake System
5. ABS & Traction Control System
6. Supplemental Restraint System
7. Theft Deterrent System
8. Wireless Door Lock Control System
9. Cruise Control System
10. Air Conditioning System
The troubleshooting procedure and how to make use of it are described on the following pages.
FOR USING OBD SCAN TOOL OR LEXUS HAND–HELD TESTER
Before using the OBD scan tool or LEXUS hand–held tester, the OBD scan tool’s instruction book
or LEXUS hand held–tester’s operator manual should be read throughly.
If the OBD scan tool or LEXUS hand–held tester cannot communicate with ECU controlled systems
when you have connected the cable of the OBD scan tool or LEXUS hand–held tester to DLC3,
turned the ignition switch ON and operated the scan tool, there is a problem on the vehicle side or tool
side.
(1)
If communication is normal when the tool is connected to another vehicle, inspect the diagnosis
data link line (Bus
line) or ECU power circuit of the vehicle.
(2)
If communication is still not possible when the tool is connected to another vehicle, the problem
is probably in the tool itself, so perform the Self Test procedures outlined in the Tester Operator’s
Manual.
IN027–02
Vehicle Brought Workshop
Customer Problem
Analysis
Symptom Confirmation
and Diagnostic Trouble
Code Check
Symptom Simulation
Diagnostic Trouble
Code Chart
Matrix Chart of Problem
Symptoms
Circuit Inspection or Parts
Inspection
Repair
Confirmation Test
End
1
2
4
3
5
6
7
8
Ask the customer about the conditions and the
environment when the problem occurred.
1
Confirm the symptoms and the problem conditions,
and check the diagnostic trouble codes.
(When the problem symptoms do not appear
during confirmation, use the symptom simulation
method described later on.)
2, 3
Check the results obtained in Step 2, then confirm
the inspection procedure for the system or the part
which should be checked using the diagnostic
trouble code chart or the matrix chart of problem
symptoms.
4, 5, 6
Check and repair the affected system or part in
accordance with the instructions in Step 6.
7
After completing repairs, confirm that the problem
has been eliminated.
(If the problem is not reproduced, perform the
confirmation test under the same conditions and
in the same environment as when it occurred for
the first time.)
8
–
INTRODUCTION
HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
IN–17
17
1997 LEXUS ES300 (RM511U)
HOW TO PROCEED WITH TROUBLESHOOTING
Carry out troubleshooting in accordance with the procedure on the following page. Here, only the basic pro-
cedure is shown. Details are provided in each section, showing the most effective methods for each circuit.
Confirm the troubleshooting procedures first for the relevant circuit before beginning troubleshooting of that
circuit.
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
Datas Problem
Constant
Sometimes ( times per day/month)
Inspector’s
Name
CUSTOMER PROBLEM ANALYSIS CHECK
IN–18
–
INTRODUCTION
HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
18
1997 LEXUS ES300 (RM511U)
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 judgement. 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 the troubleshooting section for each
system for your use.
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–19
19
1997 LEXUS ES300 (RM511U)
2.
SYMPTOM CONFIRMATION AND DIAGNOSTIC TROUBLE CODE CHECK
The diagnostic system in the LEXUS ES300 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 LEXUS
ES300.
System
Diagnostic Trouble
Code Check
Input Signal Check
(Sensor Check)
Other Diagnosis
Function
Engine
Automatic Transmission
Anti–Lock Brake System (& Traction Control)
Supplemental Restraint System
Cruise Control
(with Test Mode)
(with Test Mode)
Diagnostic Test
Mode
Diagnostic Test
Mode
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 below. If this is not done, it may, depending on the case, result in unnecessary troubleshooting
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.
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