1986 TOYOTA SUPRA catalytic converter
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See page EG±503.
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, 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 ratio.
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 concentration 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 electro-
motive force: 1 V).
The ECm judges by the electromotive force from the oxygen sensor whether the air±fuel ratio if RICH
or LEAN and controls the injection duration accordingly. However, if malfunction of the oxygen sensor
causes an output of abnormal electromotive force, the ECM is unable to perform accurate air±fuel ratio
control.
The main heated oxygen sensor include a heater which heats the Zirconia element. The heater is con-
trolled by the ECM. When the intake air volume is low (the temperature of the exhaust has is low) current
flows to the heater to heat the sensor for accurate oxygen concentration detection.)
Diagnostic Trouble Code Detecting ConditionDTC No.Trouble Area
(1) Open or short in heater circuit of main heated
oxygen sensor for 0.5 sec. or more.
(2) Main heated oxygen sensor signal voltage is
reduced to be 0.35 V and 0.70V for 60 sec.
under condition (a) ~ (d):
(2 trip detection logic)*1
(a) Engine coolant temp.: Between 80°C
(176°F) and 95°C (203°F)
(b) Engine speed: 1,500 rpm or more
(c) Load driving (Example A/T in
overdrive (5th for M/T), A/C ON, Flat
road, 80 km/h (50 mph))
(d) Main heated oxygen sensor signal
voltage: Alternating above and below
0.45V
Open or short in heater circuit of main heated
oxygen sensor
Main heated oxygen sensor heater
ECM
Main heated oxygen sensor circuit
Main heated oxygen sensor
DTC 21 Main Heated Oxygen Sensor Circuit
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±525
Page 175 of 878
CIRCUIT DESCRIPTION
To obtain a high purification rate for the Co, 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 pre-
cisely controlled so that it is always close to the stoichiometric air±fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoi-
chiometric air±fuel ratio. This characteristic is used to detect the oxygen concentration 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 sen-
sor 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: 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 duration accordingly. However, if malfunction of the oxygen sensor causes an output
of abnormal electromotive force, the ECM is unable to perform accurate air±fuel ratio control.
The main heated oxygen sensors include a heater which heats the Zirconia element. The heater is controlled
by the ECM. When the intake air volume is low t(the temperature of the exhaust has is low) current flows to
the heater to heat the sensor for accurate oxygen concentration detection.)
Flange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Heater*
1
Coating (Ceramic)
Ideal Air±Fuel Mixture
Richer Ð Air Fuel ratio Ð Leaner
Trouble AreaDTC No.Diagnostic Trouble Code Detecting Condition
Exhaust Gas
Output Voltage
(1)*1Open or snort in heater circuit of main heated
oxygen sensor for 0.5 sec. or more.
(2) (Main heated*1) 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)*
2
(a) Engine coolant temp.: Between 80°C
(176°F and 95°C (203°F)
(b) Engine speed: 1,500 rpm or more
(c) Load driving (Example A/T in Overdrive
(5th for M/T), A/C ON, Flat road, 80 km/h (50
mph))
(d) (Main heated*
1) oxygen sensor signal
voltage: Alternating above and below 0.45 V
Atmosphere
Open or short in heater circuit of main heated
oxygen sensor
Main heated oxygen sensor heater
ECM
(Main heated*
1) oxygen sensor circuit
(Main heated*1) oxygen sensor
HINT: Diagnostic trouble code ª21º is for the (main heated*1) oxygen sensor (Fr) circuit.
Diagnostic trouble code ª28º is for the (main heated*
1) oxygen sensor (Rr) circuit.
*1: Main heated oxygen sensor ONLY for California specification vehicles.
*2: See page EG±397.
DTC 21 28 (Main Heated*1) Oxygen Sensor Circuit
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±419
Page 546 of 878
EMISSION CONTROL SYSTEMS (2JZ±GTE)
SYSTEM PURPOSE
The emission control systems are installed to reduce the amount of CO, HC and NOx exhausted from the
engine ((3), (4) and (5)), to prevent the atmospheric release of blow±by gas±containing HC (1) and evapo-
rated fuel containing HC being released from the fuel tank (2).
The function of each system is shown in the following table.
System Abbreviation Function
(1) Positive Crankcase Ventilation
(2) Evaporative Emission Control
(3) Exhaust Gas Recirculation
(4) Three±way Catalytic Converter
(5) Sequential Multiport Fuel Injection*
PCV
EVAP
EGR
TWC
SFI
Reduces HC
Reduces evaporated HC
Reduces NOx
Reduces CO, HC and NOx
Injects a precisely timed, optimum amount of fuel for reduced
exhaust emissions
Remark: * For inspection and repair of the SFI system, refer to the SFI section this manual.
PREPARATION
RECOMMENDED TOOLS
09082±00050 TOYOTA Electrical Tester Set
EQUIPMENT
Tachometer
Torque wrench
Vacuum gauge
± ENGINEEMISSION CONTROL SYSTEMS (2JZ±GTE)EG±175
Page 547 of 878
EMISSION CONTROL SYSTEMS (2JZ±GTE)
SYSTEM PURPOSE
The emission control systems are installed to reduce the amount of CO, HC and NOx exhausted from the
engine ((3), (4) and (5)), to prevent the atmospheric release of blow±by gas±containing HC (1) and evapo-
rated fuel containing HC being released from the fuel tank (2).
The function of each system is shown in the following table.
System Abbreviation Function
(1) Positive Crankcase Ventilation
(2) Evaporative Emission Control
(3) Exhaust Gas Recirculation
(4) Three±way Catalytic Converter
(5) Sequential Multiport Fuel Injection*
PCV
EVAP
EGR
TWC
SFI
Reduces HC
Reduces evaporated HC
Reduces NOx
Reduces CO, HC and NOx
Injects a precisely timed, optimum amount of fuel for reduced
exhaust emissions
Remark: * For inspection and repair of the SFI system, refer to the SFI section this manual.
PREPARATION
RECOMMENDED TOOLS
09082±00050 TOYOTA Electrical Tester Set
EQUIPMENT
Tachometer
Torque wrench
Vacuum gauge
± ENGINEEMISSION CONTROL SYSTEMS (2JZ±GTE)EG±175
Page 555 of 878
THREE±WAY CATALYTIC CONVERTER
(TWC) SYSTEM
EXHAUST PIPE ASSEMBLY INSPECTION
1. CHECK CONNECTIONS FOR LOOSENSESS OR
DAMAGE
2. CHECK CLAMPS FOR WEAKNESS, CRACKS OR
DAMAGE
TWC INSPECTION
CHECK FOR DENTS OR DAMAGE
If any part of the protector is damaged or dented to the extent
that it contacts the TWC, repair or replace it.
HEAT INSULATOR INSPECTION
1. CHECK HEAT INSULATOR FOR DAMAGE
2. CHECK FOR ADEQUATE CLEARANCE BETWEEN
CATALYTIC CONVERTER AND HEAT INSULATOR
± ENGINEEMISSION CONTROL SYSTEMS (2JZ±GTE)EG±183
Page 559 of 878
EMISSION CONTROL SYSTEMS (2JZ±GE)
SYSTEM PURPOSE
The emission control systems are installed to reduce the amount of CO, HC and NOx exhausted from the
engine ((3), (4) and (5)), to prevent the atmospheric release of blow±by gas±containing HC (1) and evapo-
rated fuel containing HC being released from the fuel tank (2).
The function of each system is shown in the following table.
System Abbreviation Function
(1) Positive Crankcase Ventilation
(2) Evaporative Emission Control
(3) Exhaust Gas Recirculation
(4) Three±Way Catalytic Converter
(5) Sequential Multiport Fuel Injection*
PCV
EVAP
EGR
TWC
SFI
Reduces HC
Reduces evaporated HC
Reduces NOx
Reduces CO, HC and NOx
Injects a precisely timed, optimum amount of fuel for re-
duced exhaust emissions
Remark: * For inspection and repair of the SFI system, refer to the SFI section this manual.
PREPARATION
RECOMMENDED TOOLS
09082±00050 TOYOTA Electrical Tester Set
EQUIPMENT
Tachometer
Torque wrench
Vacuum gauge
± ENGINEEMISSION CONTROL SYSTEMS (2JZ±GE)EG±163
Page 560 of 878
EMISSION CONTROL SYSTEMS (2JZ±GE)
SYSTEM PURPOSE
The emission control systems are installed to reduce the amount of CO, HC and NOx exhausted from the
engine ((3), (4) and (5)), to prevent the atmospheric release of blow±by gas±containing HC (1) and evapo-
rated fuel containing HC being released from the fuel tank (2).
The function of each system is shown in the following table.
System Abbreviation Function
(1) Positive Crankcase Ventilation
(2) Evaporative Emission Control
(3) Exhaust Gas Recirculation
(4) Three±Way Catalytic Converter
(5) Sequential Multiport Fuel Injection*
PCV
EVAP
EGR
TWC
SFI
Reduces HC
Reduces evaporated HC
Reduces NOx
Reduces CO, HC and NOx
Injects a precisely timed, optimum amount of fuel for re-
duced exhaust emissions
Remark: * For inspection and repair of the SFI system, refer to the SFI section this manual.
PREPARATION
RECOMMENDED TOOLS
EQUIPMENT
Tachometer
Torque wrench
Vacuum gauge
± ENGINEEMISSION CONTROL SYSTEMS (2JZ±GE)EG±163
Page 568 of 878
THREE±WAY CATALYTIC CONVERTER
(TWC) SYSTEM
EXHAUST PIPE ASSEMBLY INSPECTION
1. CHECK CONNECTIONS FOR LOOSENSESS OR
DAMAGE
2. CHECK CLAMPS FOR WEAKNESS, CRACKS OR
DAMAGE
TWC INSPECTION
CHECK FOR DENTS OR DAMAGE
If any part of the protector is damaged or dented to the extent
that it contacts the TWC, repair or replace it.
HEAT INSULATOR INSPECTION
1. CHECK HEAT INSULATOR FOR DAMAGE
2. CHECK FOR ADEQUATE CLEARANCE BETWEEN
CATALYTIC CONVERTER AND HEAT INSULATOR
± ENGINEEMISSION CONTROL SYSTEMS (2JZ±GE)EG±171