Nissan Maxima QX

since 1993 release

Repair and operation of the car

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

General information

The l-probe located in a final path 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). The Verkhnepotochny oxygen sensor gives out on RSM supplies the module of management of information on the residual maintenance _{of O2} in system of production of the fulfilled gases. RSM 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.

The Nizhnepotochny l-probe does not exert impact on configuration process by the module of management of air-fuel mix. On a design and the principle of functioning the sensor is identical to verkhnepotochny. By comparison of level of content of oxygen on sites of the final highway is higher and below the RSM catalytic converter defines efficiency of functioning of the last. Remark: On models 1993 and 1994 of of the issue only one oxygen sensor is used (verkhnepotochny). On models since 1995 the issue provided two verkhnepotochny l-probes (on one on each of ranks of cylinders) and one nizhnepotochny.

It should be noted that the oxygen sensor is capable to develop alarm tension only being warmed up up to the normal working temperature (318 °C). While the sensor is in a cold state, RSM works in the mode of the OPENED CONTOUR, exercising control of configuration of air-fuel mix on the basis of the basic parameters put in it. 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: RSM 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 built in in it by the electrical wiring piece equipped with the contact plug which performance of attempts of a detachment can be led to an irreversible exit of the probe 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 the l-probe extremely carefully, 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.

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

CHECK

PERFORMANCE ORDER

Oxygen sensors are extremely sensitive to electric overloads of a chain. For connection of the voltmeter to the socket of the l-probe use the wires crossing points equipped with safety locks. Try to enter extremely carefully measuring instrument probes to the contact socket from its reverse side (see the Head Onboard electric equipment). Use only digital measuring instruments for check of sensors.

Implementation of the procedure described below can lead to entering in memory of OBD of malfunction which will be highlighted by a control lamp "Check the engine". Upon completion of check and the corresponding recovery repair do not forget to clear memory of system (see the Section System of Onboard Diagnostics (OBD) - the principle of functioning and codes of malfunctions).

1. Find the electric socket of the sensor. From a reverse side of the socket connect the positive probe of the voltmeter to the plug of a white wire (see the Head Onboard electric equipment). Ground the negative probe. Start the engine and warm up it up to the normal working temperature. Determine the size of alarm tension of the sensor by indications of the voltmeter:

a) Amplitude of the signal developed by the verkhnepotochny sensor has to lie in the range from 100 to 900 mV, actively changing in the specified limits.
b) The Nizhnepotochny sensor has to develop alarm tension in the same range (on average 400 mV), however without active changes.

2. Check serviceability of giving for the battery tension sensor. Estimate quality of grounding. Disconnect an electrical wiring from the sensor and connect the positive probe of the voltmeter to the plug of green-black (1993 and 1994) / red-black (since 1995) the contact socket (see schemes of electric connections at the end of the Head Onboard electric equipment). A negative wire connect to the plug blue / сине-желтого wires. At the included ignition the device has to register tension close to battery tension.
3. Check resistance of a heating element of the oxygen sensor. Connect an ohmmeter to two plugs of a heating element in the l-probe electrical wiring socket (from the last). Remark: The electrical wiring plait which is built in in the sensor usually has no color marking.
The required resistance makes:

a) For models 1993 and 1994 of of the issue - 3.0 ÷ 1000 Ohms;
b) For models 1995 and 1996 of of the issue - 2.3 ÷ 4.3 Ohms (verkhnepotochny sensors) and 5.2 ÷ 8.2 nizhnepotochny;
c) For models since 1997 of the issue - 2.3 ÷ 4.3 Ohms.
4. In case of break identification, or at excessively good results of measurements. Replace the corresponding sensor.

At positive results of the checks described above it is necessary to check for break and short circuit an electrical wiring on the site of a chain between the sensor and RSM. If it is not possible to reveal any deviations, the car should be driven away on car repair shop for more detailed diagnostics.

REPLACEMENT

PERFORMANCE ORDER

1. 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:

a) Oxygen sensors are equipped with the built-in electrical wiring plait with the contact socket. Damage of this plait leads to an irreversible exit of the sensor out of operation, - be careful;
b) Try not to allow hits on the contact socket and blinds of the sensor of oil, lubricant, dirt, moisture, etc.;
c) Do not apply any solvents to cleaning of the sensor at all;
d) Try not to drop and sharply not to shake the sensor.
2. The car also establish to Poddomkratta it on props.
3. Accurately disunite the socket of an electrical wiring of the oxygen sensor.

4. By means of a special key carefully turn out the probe from the corresponding section of system of production of the fulfilled gases.

5. Before a vvorachivaniye of the sensor grease its carving part with the anti-taking sealant.
6. Screw the sensor on the regular place and strongly tighten it.
7. Lower the car on the earth and connect an electrical wiring to the sensor.
8. Make the car trial runs. Check memory of the module of management for existence of codes of malfunctions.