Toyota 2GR-FE Manual page 338

ES–182
*
: The TWC has the capability to store oxygen. The OSC and the emission purification capacity of the
TWC are mutually related. The ECM determines whether the catalyst has deteriorated, based on the
calculated OSC value (See page ES-249).
HO2 SENSOR CIRCUIT LOW VOLTAGE (P0137 and P0157: OPEN):
Active air-fuel
ratio control
Target air-fuel ratio
ES
HO2 sensor
voltage
HO2 SENSOR CIRCUIT HIGH VOLTAGE (P0138 and P0158: SHORT):
Active air-fuel
ratio control
Target air-fuel ratio
HO2 sensor
voltage
Interrelation between temperature of
element and impedance:
DTC Detection Area
15,000
1,000
100
Ω
10
5
300 400
(572) (752) (932)
2GR-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
Stoichiometric
Air-Fuel Level
Stoichiometric
Air-Fuel Level
500 600 700 800
(1,112) (1,292) (1,472)
°C (°F)
A076841E09
Off
Normal
0.21 V
Off
0.59 V
4. High or Low Impedance of Heated Oxygen (HO2)
Sensor (DTCs P0136 and P0156 or P0137 and P0157)
During normal air-fuel ratio feedback control, there are
small variations in the exhaust gas oxygen
concentration. In order to continuously monitor the slight
variation of the HO2 sensor signal while the engine is
running, the impedance
the ECM. The ECM determines that there is a
malfunction in the sensor when the measured
impedance deviates from the standard range.
*
: The effective resistance in an alternating current
electrical circuit.
HINT:
• The impedance cannot be measured using an
ohmmeter.
15 to 20 seconds
Operation
Abnormal
Rich
Abnormal
Operation
Lean
*
of the sensor is measured by
Normal
Abnormal
A080024E11