General Information

P0135 O2 Sensor Heater Circuit (Bank 1 / Sensor 1)

General Information

Component Location





General Description

The heated oxygen sensors are mounted on the front side and the rear side of Catalytic Converter (warm-up catalytic converter), which detects the oxygen concentration in the exhaust gas. The front HO2S signal is used to control air/fuel ratio (closed loop fuel control) and the rear HO2S signal is used to monitor front HO2S and catalyst for proper operation. The heated oxygen sensor (HO2S) produces a voltage that varies between 0 V and 1 V. When the air/fuel ratio is lean, the oxygen concentration in the exhaust gas increases and the front HO2S outputs a low voltage (approximately 0 - 0.1 V).
When the air/fuel ratio is rich, the oxygen concentration in the exhaust gas decreases and the front HO2S output a high voltage (approximately 0.8 - 1 V). The ECM constantly monitors the HO2S and increases or decreases the fuel injection duration by using the HO2S signal, which is called closed-loop fuel control operation.

DTC Description

If ECM detects that the internal resistance of heater is out of threshold value, ECM sets DTC P0135.

DTC Detecting Condition





** S1 : upstream oxygen sensor / S2 : downstream oxygen sensor

Specification





Diagnostic Circuit Diagram





Signal Waveform & Data




The HO2S requires a minimum temperature to provide a closed loop fuel control system. So the HO2S contains a heater element to reduce its warm-up time and ensure its performance during all driving conditions. The HO2S heater is controlled ON after engine start except for Cold condition and high speed acceleration. The ECM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the ECM provides a ground circuit for activating the heater.