General description and verification
9. Oxygen sensor located in the exhaust manifold (see illustration), carries out current monitoring of the oxygen content in the exhaust gases. The oxygen contained in the exhaust gases interacts with the oxygen sensor, resulting in an output voltage that varies from 0.1 V (high oxygen content, lean mixture) up to 0.9 V (low oxygen, rich mixture). The ECM/PCM constantly analyzes this voltage to determine the air/fuel ratio in the mixture. The ECM/PCM changes the fuel/air ratio in the mixture by controlling the pulse width (opening time) fuel injectors. The ideal ratio in terms of minimizing harmful emissions and maximizing catalyst efficiency is 14.7 parts air to one part fuel. It is this ratio that the ECM/PCM, along with the oxygen sensor, tries to maintain constantly.
4.9. Make sure the engine is completely cool before removing the oxygen sensor from the exhaust manifold
10. The oxygen sensor will not output voltage if its temperature is below the normal operating temperature of approximately 320°C. During the initial warm-up period of the engine, the ECM/PCM operates in open loop mode.
11. If the engine warms up to normal operating temperature and/or runs for two minutes or more and if the oxygen sensor generates a constant voltage signal between 0.35-0.55 V even when the TPS throttle position sensor indicates that the engine is not idling, the ECM/PCM will set code 13.
12. A delay of 2 minutes or more between engine start and normal sensor operation, followed by a low voltage signal or a short circuit in the sensor circuit, will cause the ECM/PCM to set code 44. If a high voltage signal is generated, the ECM will set code 45.
13. When one of the above codes is set, the ECM/PCM operates in open loop mode, i.e. fuel management is not carried out using information from the oxygen sensor, but on the basis of a programmed mode.
14. The correct operation of the oxygen sensor depends on the fulfillment of four conditions:
- A) Electrical. The low voltages generated by the sensor depend on good, clean electrical connections, which should be checked whenever there is a suspicion or indication that the sensor is not working properly.
- b) Supply of external air. The design of the sensor is such that the gases circulate inside it. In all cases of removal, installation or replacement of the sensor, check that the channels are not clogged.
- V) Normal operating temperature. The ECM/PCM will not respond to the sensor signal until the sensor has reached a temperature of approximately 320°C. This factor must be taken into account when evaluating the characteristics of the sensor.
- G) Unleaded (free of tetraethyl lead) petrol. The sensor requires the use of unleaded fuel for proper operation.
15. In addition to fulfilling the conditions mentioned above, special care must be taken when servicing the sensor.
- A) The oxygen sensor has a non-removable flexible lead with an electrical connector, which must not be disconnected from the sensor. Damage to or disconnection of the pigtail or electrical connector from the sensor may adversely affect the operation of the latter.
- b) The sensor's electrical connector and slotted shank must be kept free of grease, dirt, and other foreign matter.
- V) Do not use any solvents to clean the oxygen sensor.
- G) Do not drop the sensor and handle it carefully.
- d) To prevent melting of the silicone sheath material and to ensure proper operation of the sensor, pay attention to the correct installation of the sheath.
Replacement
Note. Since the oxygen sensor is installed in the exhaust manifold or in the exhaust pipe, which shrink when cooled, it is quite difficult to remove it from a car with a cold engine. Therefore, in order to avoid the risk of damage to the sensor (if you plan to re-install it in a new manifold or exhaust pipe) start the engine and let it run for a minute or two, then turn it off and proceed to remove the sensor. When performing work, try not to touch hot parts to avoid burns.
16. Disconnect a wire from a negative conclusion of the storage battery.
17. Having lifted the car, establish it reliably on racks.
18. After loosening the latch, carefully disconnect the electrical connector from the sensor.
19. Carefully unscrew the sensor from the exhaust manifold.
Attention! Applying excessive force may damage the threads on the sensor body.
20. To make it easier to remove the sensor next time, an anti-corrosion compound should be applied to its threads. The thread on the new sensor is pre-coated with such a composition at the manufacturer; however, if you intend to reuse a sensor removed from the vehicle, re-coat.
21. After screwing the sensor into the manifold, tighten it tightly. Connect the electrical connector on the pigtail to the main wiring harness on the engine.
22. Lower the vehicle to the ground and connect the wire to the negative battery terminal.