Contents: Examination ↓ Replacement ↓
Oxygen sensor
1. Seat connector; 2. Secondary sensor connector; 3. Cover; 4. Clamp; 5. First sensor
The oxygen sensor is designed to generate a signal, based on which the computer determines the oxygen content in the exhaust gases and maintains the stoichiometric composition of the combustible mixture (14.7 parts air to 1 part gasoline) by changing the duration of fuel injection. A low-level signal (0.1 V) from the sensor corresponds to a lean mixture, and a high-level signal (0.9 V) to a rich mixture.
The vehicles in question are equipped with 2 oxygen sensors - at the input and output of the catalytic converter. If the sensor temperature is below 340°C, there is no signal from the sensor and until the engine warms up, the sensor-computer system operates in the open-loop mode. If after the engine warms up the signal does not exceed 0.45 V at speeds above 1500 rpm, the open-loop mode is maintained, and for processing, instead of the signal from the sensor, the default data stored in the computer memory is used.
Attention! When checking the sensor, it is prohibited to disconnect the flexible conductor from it, twist the wiring, and also subject the sensor to sharp mechanical impacts. It is prohibited to use solvents to clean the sensor.
Examination
1. Insert the voltmeter needle probes into the sensor connector, to terminals 3 (positive terminal of the voltmeter) and 4 (negative terminal) - in a 4-cylinder engine. Raise the front of the car. To access the second sensor connector, you will need to remove the front seat.
2. Start the engine and monitor the voltmeter readings as the engine warms up. On a cold engine, the voltage should be 0.1–0.2 V. On a warm engine, the voltage should begin to fluctuate within 0.1–0.9 V (closed loop mode is activated). If the closed loop mode does not turn on, or turns on with a long delay, replace the sensor.
3. Check the serviceability of the sensor heater by measuring the resistance between the HT and B+ terminals of the connector, which should be 11–16 Ohms.
(Publication Reprinted from a web portal: «ToyotaMan.ru»)
4. Check for battery voltage between the B+ terminal on the computer side of the connector and ground (the ignition must be on).
Replacement
1. Run the engine for 1-2 minutes. Disconnect the battery from the ground and lift the car.
2. Carefully disconnect the connector from the sensor and unscrew the sensor using a notched open-end wrench.