Heated Oxygen Sensor (HO2S)

HEATED OXYGEN SENSOR (HO2S)

The oxygen sensor detects the oxygen concentration in the exhaust gas and changes the signal voltage accordingly, which is sent to the engine control module. If the air-fuel mixture is richer than the stoichiometric ratio (i.e., the oxygen concentration in the exhaust gas is low), the sensor signal voltage is approximately 800 mV. If the air-fuel mixture is leaner than the stoichiometric ratio (i.e., the oxygen concentration in the exhaust gas is high), the sensor signal voltage is approximately 100 mV. Based on this signal, the engine control module adjusts fuel delivery so that the air-fuel mixture is as close as possible to the stoichiometric ratio.

CIRCUIT DIAGRAM - HEATED OXYGEN SENSOR (HO2S)

TROUBLESHOOTING HINTS

1. If the oxygen sensor is faulty, the exhaust gas will contain an increased amount of toxic substances.

2. If the oxygen sensor signal (output voltage) differs from the specified value after the sensor has been confirmed to be serviceable, the cause of the malfunction is in the air-fuel ratio control system components:

• Faulty injector • Air leaking into the intake manifold through a damaged gasket • Faulty manifold absolute pressure (MAP) sensor, evaporative emission purge solenoid valve, or engine coolant temperature sensor.

• Poor connection or incorrectly connected connectors.

INSPECTION USING A VOLTMETER OR HI-SCAN (PRO) SCAN TOOL

If the accelerator pedal is released quickly while the engine is running at 4000 rpm, the fuel supply will be cut off for a short time, and the HI-SCAN (Pro) scan tool will show an oxygen sensor signal voltage of 200 mV or less.

If the accelerator pedal is depressed quickly, the air-fuel mixture will be enriched and the tester will show an oxygen sensor signal voltage of 600 - 1000 mV.

If the engine is running at idle, the oxygen sensor signal voltage will fluctuate between 200 mV or lower and 600 - 1000 mV. In this case, the oxygen sensor can be considered normal.

WIRING INSPECTION (FOR 1.6L I4 ENGINE)

WIRING INSPECTION (FOR 1.8/2.0L I4 ENGINES)

SENSOR INSPECTION

1. Before inspection, warm up the engine until the engine coolant temperature reaches 80 - 95 °C.

2. Use a high-precision digital voltmeter when taking measurements.

If the oxygen sensor is faulty, replace it.

Oxygen sensor tightening torque: 50 - 60 N·m