Diag. Code
21
Main Oxygen Sensor and Heater Signal
CIRCUIT DESCRIPTION
The main oxygen sensor is located in the exhaust manifold. It indirectly determines whether the fuel
mixture is rich or lean by detecting the concentration of oxygen present in the exhaust gas.
The main oxygen sensor is provided with a heater. The heater is controlled by the ECU. When the
intake air volume is low (the temperature of the exhaust gas is low) current flows to the heater to heat
the sensor for accurate detection.
Code No.
Diagnosis
Trouble Area
(1) Open or short in heater circuit of main oxygen
sensor for 0.5 sec. or more (HT).
•
Open or short in heater circuit of
main oxygen sensor
•
Main oxygen sensor heater
•
ECU
21
(2) At normal driving speed (below 60 mph and
engine speed is above 1,500 rpm), amplitude
of oxygen sensor signal (OX1) is reduced to
between 0.35–0.70 V continuously for 60
sec. or more
(2 trip detection logic)*
•
Open or short in main oxygen sen-
sor circuit
•
Main oxygen sensor
•
ECU
*: See page
TR–36
–
ENGINE TROUBLESHOOTING
Circuiit Inspection
Summary of Contents for 2VZ-FE
Page 1: ...ENGINE MECHANICAL EM 1 ENGINE MECHANICAL Description Operation ...
Page 31: ...CYLINDER HEADS COMPONENTS EM 29 ENGINE MECHANICAL Cylinder Heads ...
Page 63: ...CYLINDER BLOCK REMOVAL OF ENGINE EM 61 ENGINE MECHANICAL Cylinder Block ...
Page 64: ...EM 62 ENGINE MECHANICAL Cylinder Block ...
Page 71: ...COMPONENTS EM 69 ENGINE MECHANICAL Cylinder Block ...
Page 106: ...EFI SYSTEM FI 1 ...
Page 107: ...DESCRIPTION FI 2 EFI SYSTEM Description ...
Page 111: ...OPERATION System Circuit FI 4 EFI SYSTEM Operation System Circuit ...
Page 121: ...FUEL SYSTEM Fuel Pump EFI SYSTEM Fuel System Fuel Pump FI 15 ...
Page 141: ...Fuel Tank and Lines COMPONENTS EFI SYSTEM Fuel System Fuel Tank and Lines FI 35 ...
Page 172: ...EXHAUST SYSTEM EXHAUST SYSTEM REPAIR INSTRUCTIONS EX 1 ...
Page 174: ...EMISSION CONTROL SYSTEMS EC 1 ...
Page 186: ...COOLING SYSTEM CO 1 ...
Page 205: ...LUBRICATION SYSTEM LUBRICATION SYSTEM Description Operation LU 1 ...
Page 224: ...IGNITION SYSTEM IG 1 ...
Page 237: ...SERVICE SPECIFICATIONS IG 14 IGNITION SYSTEM ServiceSpecifications ...
Page 238: ...ENGINE TROUBLESHOOTING TR 1 ...