Lexus ES300 (1997 year). Service manual — part 489
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–20
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INTRODUCTION
HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
20
1997 LEXUS ES300 (RM511U)
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.
V07268
VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
WIRE HARNESS
PARTS AND SENSOR
1
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
malfunction 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–21
21
1997 LEXUS ES300 (RM511U)
3.
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 condition 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 ex-
ternal 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 of course 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 symp-
toms 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 symp-
toms at the same time. Refer to the matrix chart of problem symptoms for each system to narrow down the
possible causes of the symptom.
V07469
HEAT METHOD: When the problem seems to occur when the suspect area is heated.
2
NOTICE:
(1) Do not heat to more than 60
°
C (140
°
F). (Temperature
is limited not to damage the components.)
(2) Do not apply heat directly to parts in the ECU.
3
WATER SPRINKLING METHOD:
NOTICE:
(1) Never sprinkle water directly into the engine
compartment, but indirectly change the temperature and
humidity by applying water spray onto the radiator front
surface.
(2) Never apply water directly onto the electronic
components.
4
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.
ON
(Service 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
IN–22
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INTRODUCTION
HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
22
1997 LEXUS ES300 (RM511U)
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–26)
P0101
(DI–31)
Mass Air Flow Circuit
Range/Performance Problem
Mass air flow meter
P0115
(DI–37)
Open or short in intake air temp. sensor circuit
Intake air temp. sensor
ECM
Intake Air Temp. Circuit Malfunction
P0110
(DI–32)
Engine Coolant Temp. Circuit
Range/Performance Problem
Open or short in engine coolant temp. sensor circuit
Engine coolant temp. sensor
ECM
P0120
(DI–43)
Throttle/ Pedal Position Sensor/Switch
”A” Circuit Range/Performance
P0116
(DI–41)
Throttle/Pedal Position Sensor/Switch
”A” Circuit Malfunction
Insufficient Coolant Temp. for Closed
Engine coolant temp. sensor
Cooling system
Engine Coolant Temp. Circuit
Malfunction
Open or short in throttle position sensor circuit
Throttle position sensor
ECM
Throttle position sensor
Open or short in heated oxygen sensor circuit
Heated oxygen sensor
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.
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INTRODUCTION
HOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMS
IN–23
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1997 LEXUS ES300 (RM511U)
4.
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.
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