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O2 Sensor (Bank 1, Sensor 2) Heater Circuit Malfunction
DTC
P0141
O2 Sensor (Bank 1, Sensor 2) Heater Circuit Malfunction - Heater
Open or Short
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 the most efficient use of the three-
way catalytic converter, the ratio of the air must be precisely controlled so that it is
always close to the stoichiometric air-fuel ratio. The HO2S 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 HO2S
informs the ECU of the LEAN condition. When the air-fuel ratio is RICHER than the
stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and
the HO2S informs the ECU of the RICH condition.
The ECU determines by the electromotive force from the HO2S whether the air-fuel
ratio is RICH or LEAN and controls the injection time accordingly. However, if
malfunction of the HO2S causes output of abnormal electromotive force, the ECU is
unable to perform an accurate air-fuel ratio control. The HO2S include a heater which
heats the sensing element. 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 oxygen concentration detection.
* HO2S : Heated Oxygen Sensor, O2 Sensor
TROUBLESHOOTING GUIDE
DTC detection condition
Background
a. ECU checks whether the heater current is within a
specified range when the heater is energized.
Check Area
a. Battery voltage is between 12 and 16V.
Judgment Criteria
a. The heater current of the front HO2S heater (Bank 1
Sensor 1 and Bank 2 Sensor 1) has continued to be
0.2 A or less, or 3.5 A or higher for 6 sec.
Diagnostic item
a. Open or shorted HO2S
heater circuit
b. Open circuit in HO2S
heater
c. ECU failed
Probable cause
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