Checking the oxygen sensor with heater (2.7L engine) (Hyundai Sonata EF)

Contents: General information ⇓ Troubleshooting Guide ⇓ Checking with a tester ⇓ Checking with a voltmeter ⇓

General information

Models with a 2.7L engine are equipped with a titanium oxygen sensor (TiO2).

The oxygen sensor determines the concentration of oxygen in the exhaust gases and accordingly changes the voltage of the signal that goes to the electronic engine control unit. If the composition of the air-fuel mixture is richer than the stoichiometric ratio (i.e. if the concentration of oxygen in the exhaust gases is small), then the voltage of the sensor signal is approximately 0 V.

If the air-fuel mixture is leaner than the stoichiometric ratio (i.e. if the concentration of oxygen in the exhaust gases is high), then the sensor signal voltage is approximately 5 V. Based on this signal, the electronic engine control unit regulates the fuel supply to the cylinders so that the composition of the air-fuel mixture is as close as possible to the stoichiometric ratio.

The oxygen sensor is equipped with a heater, which ensures stable operation of the sensor in all modes.

Note: The images below show one option for the front and rear oxygen sensors (two sensors before the pre-catalytic converter and two after it), but there is another option with one front and one rear oxygen sensor.

Front sensor (left cylinder head).

Rear sensors.

Troubleshooting Guide

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

2. If the oxygen sensor signal (output voltage) differs from the nominal value after the test showed the sensor to be in good condition, then the cause of the malfunction is in the components of the air-fuel mixture control system:

a) Injector malfunction.
b) Air enters the intake manifold through a damaged gasket.
c) Malfunction of the air flow sensor, intake manifold air temperature sensor and coolant temperature sensor.

Checking with a tester

1. Perform an oxygen sensor test when the engine is warm (the air-fuel mixture will become leaner when the engine speed is reduced, and richer when the accelerator pedal is pressed).

a) Measure the nominal value under sudden deceleration from 4000 rpm.
Nominal value: 300-900 mV
b) Measure the nominal value with a rapid increase in crankshaft speed.
Nominal value: 4000-4800 mV

2. Perform an oxygen sensor test when the engine is warm (using signals from the oxygen sensor, check the composition of the air-fuel mixture and the quality of engine control (electronic control unit)).

a) Measure the nominal value at idle speed.
Nominal value: 300-4800 mV
b) Measure the nominal value at a crankshaft speed of 2000 rpm.
Nominal value: 300-4800 mV

Checking with a voltmeter

1. Disconnect the oxygen sensor connector and measure the resistance between terminals "3" and "4" of the sensor.

(The original text is published on the website HyundaiBook.ru)

Note: Before checking, warm up the engine until the coolant temperature reaches 80-95°C.

a) Check that the resistance is 4.0-5.2 Ohm at 23°C.
b) Check that the resistance is 8.2-11.1 Ohm at 400°C.

2. Connect the power supply (battery voltage) directly to terminals "3" and "4" of the sensor.

Note: Be careful when performing this operation. Incorrect power connection or short-circuiting of terminals will damage the oxygen sensor.

3. Connect a digital voltmeter between terminals "1" and "2" of the sensor.

4. Periodically pressing the accelerator pedal, measure the output voltage of the oxygen sensor.