CIRCUIT DESCRIPTION
To obtain a high purification rate for the C0, HC and NOx components of the exhaust gas, a three±
way catalytic converter is used, but for most efficient use of the three±way catalytic converter, the
air±fuel ratio must be precisely controlled so that it is always close to the stoichiometric air±fuel ra-
tio. The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the
vicinity of the stoichiometric air±fuel ratio. This characteristic is used to detect the oxygen con-
centration in the exhaust gas and provide feedback to the computer for control of the air±fuel ratio.
When the air±fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the
oxygen sensor informs the ECM of the LEAN condition (small electromotive force; 0 V).
When the air±fuel ratio is RICHER than the stoichiometric air±fuel ratio the oxygen concentration in
the exhaust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large
electromotive force: 1 V). The ECM judges by the electromotive force from the oxygen sensor
whether the air±fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if
malfunction of the oxygen sensor causes output of abnormal electromotive force, the ECM is un-
able to perform accurate air±fuel ratio control.
Main oxygen sensor signal voltage is reduced to
between 0.35 V and 0.70 V for 60 sec. under
conditions (a) ± (d).
(2 trip detection logic) *
(a) Engine coolant temp. : 80C (176F) or more.
(b) Engine speed : 1,500 rpm or more.
(c) Load driving (EX. A/T in overdrive (5th for
M/T), A/C ON, Flat road, 50 mph (80km/h)).
(d) Main oxygen sensor signal voltage :
Alternating above and below 0.45 V.Diagnostic Trouble Code Detecting Condition
wMain oxygen sensor circuit.
wMain oxygen sensor.
*See page EG1±307Trouble Area
DTC 21 Main Oxygen Sensor Circuit
DTC No.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±352
DI00H±08
FI0534
S05331
TOYOTA Hand±Held Tester
DLC3
± DIAGNOSTICSENGINE (5S±FE)
DI±3
238 Author: Date:
PRE±CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect to the vehicle the OBD II scan
tool complying with SAE J1978 or TOYOTA hand±
held tester, and read off various data output from
the vehicle's ECM.
OBD II regulations require that the vehicle's on±
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the emission control
system / components or in the powertrain control
components which affect vehicle emissions, or a
malfunction in the computer. In addition to the MIL
lighting up when a malfunction is detected, the ap-
plicable Diagnostic Trouble Code (DTC) prescribed
by SAE J2012 are recorded in the ECM memory.
(See page DI±16)
If the malfunction does not reoccur in 3 consecutive trips, the
MIL goes off automarially but the DTCs remain recorded in the
ECM memory.
To check the DTCs, connect the OBD II scan tool or
TOYOTA hand±held tester to Data Link Connector
3 (DLC3) on the vehicle. The OBD II scan tool or
TOYOTA hand±held tester also enables you to
erase the DTCs and check freezed frame data and
various forms of engine data (For operating instruc-
tions, see the OBD II scan tool's instruction book.)
DTCs include SAE controlled codes and manufac-
turer controlled codes. SAE controlled codes must
be set as prescribed by the SAE, while manufactur-
er controlled codes can be set freely by the
manufacturer within the prescribed limits. (See DTC
chart on page DI±16)
DI07A±06
FI0534
A06134
TOYOTA Hand±Held Tester
± DIAGNOSTICSENGINE (1MZ±FE)
DI±197
432 Author: Date:
PRE±CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect to the vehicle the OBD II scan
tool complying with SAE J1978 or TOYOTA hand±
held tester, and read off various data output from
the vehicle's ECM.
OBD II regulations require that the vehicle's on±
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the emission control
system/components or in the powertrain control
components which affect vehicle emissions, or a
malfunction in the computer. In addition to the MIL
lighting up when a malfunction is detected, the ap-
plicable Diagnostic Trouble Codes (DTC) pre-
scribed by SAE J2012 are recorded in the ECM
memory (See page DI±211).
If the malfunction does not reoccur in 3 consecutive trips, the
MIL goes off but the DTCs remain recorded in the ECM memory.
To check the DTC, connect the OBD II scan tool or
TOYOTA hand±held tester to Data Link Connector
3 (DLC3) on the vehicle. The OBD II scan tool or
TOYOTA hand±held tester also enables you to
erase the DTC and check freezed frame data and
various forms of engine data (For operating instruc-
tions, see the OBD II scan tool's instruction book.).
DTC include SAE controlled codes and manufac-
turer controlled codes. SAE controlled codes must
be set as prescribed by the SAE, while manufactur-
er controlled codes can be set freely by the
manufacturer within the prescribed limits (See DTC
chart on page DI±211).
DI02W±02
FI0534
S05335
TOYOTA hand±held tester
DLC3
± DIAGNOSTICSAUTOMATIC TRANSAXLE (A140E)
DI±389
624 Author: Date:
PRE±CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect an OBD II scan tool complying
with SAE J1987 or TOYOTA hand±held tester to the
vehicle, and read off various data output from the
vehicle's ECM.
OBD II regulations require that the vehicle's on±
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the computer itself or
in drive system components which affect vehicle
emissions. In addition to the MIL lighting up when
a malfunction is detected, the applicable DTCs pre-
scribed by SAE J2012 are recorded in the ECM
memory (See page DI±16).
If the malfunction only occurs in 3 trips, the MIL goes
off but the DTCs remain recorded in the ECM
memory.
To check the DTCs, connect an OBD II scan tool or
TOYOTA hand±held tester to DLC3 on the vehicle.
The OBD II scan tool or TOYOTA hand±held tester
also enables you to erase the DTCs and check
freeze frame data and various forms of engine data
(For instruction book).
DTCs include SAE controlled codes and Manufac-
turer controlled codes.
SAE controlled codes must be set as the codes pre-
scribed by the SAE, while Manufacturer controlled
codes can be set freely by the manufacturer within
the prescribed limits.
(See DTC chart on page DI±401)
FI0534
DI02E±02
S05335
TOYOTA hand±held tester
DLC3
DI±438
± DIAGNOSTICSAUTOMATIC TRANSAXLE (A541E)
673 Author: Date:
PRE±CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect to the vehicle an OBD II scan
tool complying with SAE J1987 or TOYOTA hand±
held tester, and read off various data output from
the vehicle's ECM.
OBD II regulations require that the vehicle's on±
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the computer itself or
in drive system components which affect vehicle
emissions. In addition to the MIL lighting up when
a malfunction is detected, the applicable DTCs pre-
scribed by SAE J2012 are recorded in the ECM
memory. (See page DI±211)
If the malfunction only occurs in 3 trips, the MIL goes
off but the DTCs remain recorded in the ECM
memory.
To check the DTCs, connect an OBD II scan tool or
TOYOTA hand±held tester to DLC3 on the vehicle.
The OBD II scan tool or TOYOTA hand±held tester
also enables you to erase the DTCs and check
freeze frame data and various forms of engine data
(For instruction book).
DTCs include SAE controlled codes and Manufac-
turer controlled codes.
SAE controlled codes must be set as prescribed by
the SAE, while Manufacturer controlled codes can
be set freely by the manufacturer within the pre-
scribed limits (See DTC chart on page DI±449).