Toyota 2GR-FE Manual page 509

DTC P2195
DTC P2196
DTC P2197
DTC P2198
DESCRIPTION
HINT:
• Although the DTC titles include oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
• Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and
located near the engine assembly.
The A/F sensor generates voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is
used to provide the ECM with feedback so that it can control the air-fuel ratio. The ECM determines the
deviation from the stoichiometric air-fuel ratio level, and regulates the fuel injection time. If the A/F sensor
malfunctions, the ECM is unable to control the air-fuel ratio accurately.
The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte
(zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust
gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate
oxygen concentration detection. In addition, the sensor and heater portions are narrower than the
conventional type. The heat generated by the heater is conducted to the solid electrolyte through the
alumina, therefore the sensor activation is accelerated.
A three-way catalytic converter (TWC) is used in order to convert the carbon monoxide (CO), hydrocarbon
(HC), and nitrogen oxide (NOx) into less harmful substances. To allow the TWC to function effectively, it is
necessary to keep the air-fuel ratio of the engine near the stoichiometric air-fuel ratio.
*: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is
converted to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors
will show a constant voltage.
2GR-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1
Sensor 1)
Oxygen (A/F) Sensor Signal Stuck Rich (Bank 1
Sensor 1)
Oxygen (A/F) Sensor Signal Stuck Lean (Bank 2
Sensor 1)
Oxygen (A/F) Sensor Signal Stuck Rich (Bank 2
Sensor 1)
ES–353
ES