8.12. Check of serviceability of a state and replacement of the oxygen sensor (l-probe)

The l-probe located in a final collector of the engine traces the content of oxygen in a stream of the fulfilled gases. At contact of the molecules O2 with a sensitive element of the probe the sensor develops an amplitude signal in the range from 0.1 to 0.9 V, depending on concentration of oxygen. And, to value 0.1 B there corresponds the high content of O2 (the grown poor mix), and to value 0.9 B – low (the enriched mix). ECM/PCM continuously controls the signal arriving from the oxygen sensor, in case of need issuing commands for correction of composition of air-fuel mix due to change of duration of opening of injectors of injection. The optimum ratio of components of gas mixture guaranteeing the minimum fuel consumption at the most effective functioning of the catalytic converter makes 14.7 parts of air on 1 part of fuel, – its module of management also tries to support constantly, being guided by information arriving from the l-probe.

It should be noted that the oxygen sensor is capable to develop alarm tension only being warmed up up to the normal working temperature (about 320 °C). While the sensor is in cold condition of ECM/PCM works in the mode of the OPENED CONTOUR.

If at the engine which is warmed up up to the normal working temperature and/or working within not less than two minutes the oxygen sensor develops a stable signal with an amplitude of 0.45 V (at turns not lower than 1500 a minute), the system of self-diagnostics brings in memory of ECM/PCM the corresponding code of malfunction (see Check of serviceability of a state and replacement of the sensor of VMT/provision of a cranked shaft / situation of pistons in cylinders of the engine (TDC/CKP/CYP)). The code is brought also in case of detection of malfunction in a sensor heater chain.

In case of violation of serviceability of functioning of the l-probe or its chain of ECM/PCM passes into the mode of the opened contour, ignoring information arriving from the sensor and supporting composition of air-fuel mix at some set level providing sufficient efficiency of return of the engine.

Serviceability of functioning of the oxygen sensor depends on performance of set of some certain conditions:

   a) Electric parameters: Stability of the amplitude signal of low voltage developed by the sensor to a large extent depends on quality of contact connections of a chain of the l-probe which should be checked first of all in case of problems;
   b) Supply of external air: The design of the l-probe provides free circulation of external air in the sensor. At installation of the probe always check passability of air channels;
   c) Working temperature: ECM/PCM begins to react to information arriving from the l-probe only after the sensor is heated-up up to the normal working temperature (about 320 °C). it is necessary not to lose sight of this fact when checking serviceability of functioning of the probe;
   d) Quality of fuel: Correct functioning of the l-probe becomes possible only on condition of application for gas station of the car of UNLEADED fuel!

In addition to the conditions listed in the previous paragraph at service of the l-probe it is necessary to observe some special precautionary measures:

   a) The oxygen sensor is equipped tightly with the electrical wiring piece which is built in in it and equipped with the contact plug which attempts of a detachment can lead to an irreversible exit of the sensor out of operation;
   b) Try not to allow hits in blinds of the sensor or its electric socket of dirt and lubricant;
   c) Do not use any solvents for cleaning of the oxygen sensor;
   d) Handle with the l-probe extremely with care, do not drop it and try not to shake;
   e) The silicone protective cover has to put on on the sensor strictly definitely not to be melted and not to break serviceability of functioning of the probe.

Check

 PERFORMANCE ORDER

1. Find the electric socket of the sensor. From a reverse side of the socket enter the unbent office paper clip into a nest of contact of an alarm wire (white or white-red) (see an accompanying illustration).

Identification of contact plugs of the socket can be made by means of schemes of electric connections (see the Head Onboard electric equipment). Connect the positive probe of the voltmeter to a paper clip, ground a negative conclusion.

Colors of isolation of an electrical wiring of the l-probe are given also in schemes of electric connections (see the Head Onboard electric equipment).

2. You monitor indications of the measuring instrument (mV) in the course of an engine warming up.
3. At the initial stage the cold sensor has to develop a constant signal with an amplitude of 0.1÷0.2 V (the mode of the opened contour). About two minutes later the engine will reach the normal working temperature and the indication of the sensor will begin to fluctuate ranging from 0.1 to 0.9 B (the mode of the closed contour). If the system does not pass into the mode of the closed contour, or passes with unacceptably big delay (the lazy sensor), replace the l-probe.
4. Check also serviceability of functioning of the heater of the oxygen sensor. Disunite the socket of an electrical wiring of the probe and connect an ohmmeter between heater plugs (see schemes of electric connections in the Head Onboard electric equipment of the present manual). Nominal resistance makes 10÷40 of Ohms.
5. Check serviceability of giving of food for the heater. Disunite the electric socket and measure tension on it from a plait (again address schemes of electric connections). At the included ignition (do not start the engine) the voltmeter has to fix battery tension. If food is absent, check a condition of an electrical wiring on the site of a chain between the main relay, ECM/PCM and the oxygen sensor.
6. At negative results of the listed above checks, replace the l-probe.

Replacement

 PERFORMANCE ORDER

The l-probe reversing on the cold engine can be extremely difficult in view of thermal compression of metal of a final collector / pipe of system of release. In order to avoid risk of damage of components before starting removal of the sensor warm up the engine during a couple of minutes – try not to burn about the warmed surfaces in the course of implementation of the procedure.

1. Disconnect a negative wire from the battery. The car also establish to Poddomkratta it on props.

If the stereosystem established on the car is equipped with a security code before disconnecting the battery make sure that you have the correct combination for input of the audio system in action!


2. Disunite the socket of an electrical wiring of the oxygen sensor.

3. Accurately turn out the probe from a final collector (see an accompanying illustration).

4. Before a sensor vvorachivaniye into place grease its carving part with the anti-taking sealant (new sensors are usually already covered by the corresponding structure).
5. Screw the sensor on the regular place and strongly tighten it.
6. Connect an electrical wiring.
7. Lower the car on the earth and make its trial runs. Check memory of the module of management for existence of codes of malfunctions.