P0135

DTC P0135 O2 Sensor (Bank 1, Sensor 1) 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

DTC Detection Condition:

Circuit Diagram:

Part 1:

Part 2:

TEST PROCEDURE