Nissan Maxima QX

since 1993 of release

Repair and car operation

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

General information

Located in a final path of the engine the l-probe traces the content of oxygen in a stream of the fulfilled gases. At contact of molecules _О2 to a sensitive element of a probe the sensor develops a peak signal in a range from 0.1 to 0.9 In, depending on concentration of oxygen. And, to value 0.1 In there corresponds high contents _О2 (the grown poor mix), and to value 0.9 In - low (the enriched mix). The Verkhnepotochny oxygen sensor gives out on RSM supplies the module of management with information on residual contents _О2 in system of production of the fulfilled gases. RSM continuously supervises a signal arriving from the oxygen sensor, in case of need giving out commands for correction of structure of an air and fuel mix at the expense of change of duration of opening of injectors of injection. The optimum ratio of components of the 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 and tries to support constantly, being guided by information arriving from a l-probe.

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

It should be noted that the oxygen sensor is capable to develop alarm tension only being heated-up to normal working temperature (318°С). While the sensor is in a cold condition, RSM works in a mode of the OPENED CONTOUR, exercising administration of configuration of an air and fuel mix on the basis of the base 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 a peak signal of a low voltage developed by the sensor in big degree depends on quality of contact connections of a chain of a l-probe which should be checked first of all in case of problems;
b) Supply of external air: The design of a l-probe provides free circulation of external air in the sensor. At probe installation always check passableness of air channels;
c) Working temperature: RSM starts to react to information arriving from a l-probe only after the sensor will be heated-up to normal working temperature (near 320°С). It is necessary not to lose sight of this fact at check of serviceability of functioning of a probe;
d) Quality of fuel: Serviceable functioning of a l-probe becomes possible only under condition of application for filling of the car of UNLEADED fuel!

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

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

In case of violation of serviceability of functioning of a l-probe or its chain of RSM passes to a mode of the opened contour, ignoring information arriving from sensors and supporting structure of an air and 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 voltmeter connection to the socket of a l-probe use the equipped safety locks wires crossing points. Try to enter extremely carefully щупы a measuring instrument to the contact socket from its reverse side (see. Head Onboard electric equipment). Use for check of sensors only digital measuring instruments.

Performance described below procedure can lead to entering in memory of OBD of malfunction which will be highlighted by a control lamp “Check the engine”. On termination of check and the corresponding regenerative repair do not forget to clear memory of system (see. The section System of onboard diagnostics (OBD) - a principle of functioning and codes of malfunctions).

1. Find the electric socket of the sensor. From a reverse side of the socket connect positive щуп the voltmeter to the plug of a white wire (see. Head Onboard electric equipment). Negative щуп earth. Start the engine and warm up it to normal working temperature. By indications of the voltmeter determine size of alarm tension of the sensor:

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

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

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

At positive results described above checks it is necessary to check on break and short circuit electroconducting on a chain site 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 appear the extremely inconvenient in view of thermal compression of metal final collectors/pipes of system of release. In order to avoid risk of damage of components before starting sensor removal, warm up the engine during few minutes, - try not to burn about the warmed-up surfaces in the course of procedure performance:

a) Oxygen sensors are equipped with the built-in plait of electroconducting 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 a jalousie of the sensor of oil, greasing, dirt, moisture, etc.;
c) At all do not apply to sensor cleaning any solvents;
d) Try not to drop and sharply not to shake the sensor.
2. To Poddomkratta the car also establish it on props.
3. Accurately disunite the socket of electroconducting of the oxygen sensor.

4. By means of a special key carefully turn out a 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 anti-taking hermetic.
6. Screw the sensor on the regular place and strongly tighten it.
7. Lower the car on the earth and connect to the sensor electroconducting.
8. Make the car trial runs. Check memory of the module of management on existence of codes of malfunctions.