Lexus ES300 (2002 year). Manual — part 361
Ie-4-2-D
A30590
HT
+B
E1
OX
A52108
A56997
Bank 1
Bank 2
HT
+B
OX
E1
HT
+B
OX
E1
A54408
E2
HT2B
HT1B
E8
05-64
-
DIAGNOSTICS
SFI SYSTEM (1MZ-FE)
217
2002 LEXUS ES300 REPAIR MANUAL (RM911U)
2
INSPECT OXYGEN NO.2 SENSOR
(a)
Disconnect the oxygen sensor connector.
(b)
Measure resistance between the terminals HT and +B of
the oxygen sensor.
Resistance: 11 - 16
Ω
(20
C)
NG
REPLACE OXYGEN NO.2 SENSOR
OK
3
CHECK HARNESS AND CONNECTOR(ECM - OXYGEN SENSOR)
(a)
Disconnect the oxygen sensor connector.
(b)
Disconnect the ECM E8 connector.
(c)
Check for open between the terminals HT of the oxygen
sensor connector and HT1B, HT2B of the ECM connec-
tor.
Resistance: 1
Ω
or less
(d)
Check for short between the terminals HT1B, HT2B and
E2 of the ECM connector.
Resistance: 1 M
Ω
or more
NG
REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
A59656
5
A56997
Bank 1
Bank 2
HT
+B
OX
E1
HT
+B
OX
E1
-
DIAGNOSTICS
SFI SYSTEM (1MZ-FE)
05-65
218
2002 LEXUS ES300 REPAIR MANUAL (RM911U)
4
CHECK HARNESS AND CONNECTOR(OXYGEN SENSOR - E.F.I. ECU RELAY)
(a)
Disconnect the battery negative (-) terminal.
(b)
Disconnect the oxygen sensor connector.
(c)
Check for open between the terminals 5 of the E.F.I. ECU
relay side connector and +B of the oxygen sensor con-
nector.
Resistance: 1
Ω
or less
NOTICE:
Do not insert the tester leads hard in the procedure (c), or
the holder may be damaged.
NG
REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
CHECK CHECK FOR ECM POWER SOURCE CIRCUIT
05-66
-
DIAGNOSTICS
SFI SYSTEM (1MZ-FE)
219
2002 LEXUS ES300 REPAIR MANUAL (RM911U)
DTC
P0171
SYSTEM TOO LEAN(FUEL TRIM)(BANK1)
DTC
P0172
SYSTEM TOO RICH(FUEL TRIM)(BANK1)
DTC
P0174
SYSTEM TOO LEAN (FUEL TRIM)(BANK2)
DTC
P0175
SYSTEM TOO RICH (FUEL TRIM)(BANK2)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared against the basic injection time. Fuel trim
includes short-term fuel trim and long-term fuel trim.
Short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at its ideal
theoretical value. The signal from the heated oxygen sensor indicates whether the air-fuel ratio is RICH or
LEAN compared to the ideal theoretical value, triggering a reduction in fuel volume if the air-fuel ratio is rich,
and an increase in fuel volume if it is lean.
Long-term fuel trim is overall fuel compensation carried out long-term to compensate for continual deviation
of the short-term fuel trim form the central value due to individual engine differences, wear over time and
changes in the usage environment.
If both the short-term fuel trim and long-term fuel trim are LEAN or RICH beyond a certain value, it is de-
tected as a malfunction and the check engine warning (MIL) lights up.
DTC No.
DTC Detecting Condition
Trouble Area
P0171
P0174
When air fuel ratio feedback is stable after warming up engine,
fuel trim is considerably in error on RICH side
(2 trip detection logic)
Air intake (hose loose)
Fuel line pressure
Injector blockage
Open or short in A/F sensor circuit
A/F sensor malfunction
Intake air flow meter
E.F.I. engine coolant temperature sensor
Gas leakage on exhaust system
PCV hose connection
P0172
P0175
When air fuel ratio feedback is stable after warming up engine,
fuel trim is considerably in error on LEAN side
(2 trip detection logic)
Air induction system
Fuel line pressure
Injector blockage
Open or short in A/F sensor circuit
A/F sensor malfunction
Intake air flow meter
E.F.I. engine coolant temperature sensor
Gas leakage on exhaust system
PCV hose connection
HINT:
If the total of the short-term fuel trim value and long-term fuel trim value is within
±
25 %, the system is func-
tioning normally.
WIRING DIAGRAM
Refer to DTC P0125 on page
051X8-06
-
DIAGNOSTICS
SFI SYSTEM (1MZ-FE)
05-67
220
2002 LEXUS ES300 REPAIR MANUAL (RM911U)
INSPECTION PROCEDURE
HINT:
Read freed frame data using hand-held tester. Because freeze frame records the engine conditions when
the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was run-
ning or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.
1
CHECK AIR INDUCTION SYSTEM (See page
NG
REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK
2
CHECK CONNECTION OF PCV HOSE
NG
REPAIR OR REPLACE PCV HOSE
OK
3
INSPECT FUEL INJECTOR ASSY (See page
NG
REPLACE FUEL INJECTOR ASSY
OK
4
INSPECT INTAKE AIR FLOW METER SUB-ASSY (See page
)
NG
REPLACE INTAKE AIR FLOW METER
SUB-ASSY
OK
5
INSPECT E.F.I. ENGINE COOLANT TEMPERATURE SENSOR
(See page
)
NG
REPLACE E.F.I. ENGINE COOLANT
TEMPERATURE SENSOR
OK
6
CHECK FOR SPARK AND IGNITION (See page
NG
GO TO IGNITION SYSTEM
OK
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