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Check and replacement of the oxygen gauge (l-probe)
general information
Located in the exhaust path of the engine l-probe monitors the oxygen content of the exhaust stream. Upon contact with molecular O 2 sensor probe generates a sensor signal amplitude in the range of 0.1 to 0.9 V, depending on the oxygen concentration. Moreover, the value of 0.1 V corresponds to a high content of O 2 (lean mixture), and the value of 0.9 V - low (rich mixture). Verhnepotochny oxygen sensor outputs in the PCM control module supplies the residual O 2 content in the exhaust system. PCM continuously monitors the incoming signal from the oxygen sensor, if necessary, issuing commands to the adjustments of the air-fuel mixture by changing the duration of opening of injectors of injection. The optimum mixing ratio of the combustible mixture that ensures minimum fuel consumption with the most efficient functioning of the catalytic converter is 14.7 parts of air to 1 part fuel - is its control module, and continuously strives to support, focusing on coming with l-probe information.
Nizhnepotochny l-probe does not affect the build process control module air-fuel mixture. By construction and operation of the sensor is identical verhnepotochnomu. By comparing the level of oxygen in the exhaust tract areas above and below the catalytic converter PCM determines the efficiency of the latter. Note: On models 1993 and 1994 Vol. It uses only one oxygen sensor (verhnepotochny). On models since 1995 Vol. There are two verhnepotochnyh l-probe (one for each of the series of cylinders) and one nizhnepotochny.
It should be noted that the oxygen sensor is capable of producing a signal voltage only being warmed up to normal operating temperature (318 ?� C). While the sensor is cold, the PCM operates in open-loop control arrangement implementing an air-fuel mixture on the basis laid down in a basic parameters. Serviceability of functioning of the oxygen sensor depends on the aggregate performance of some specific conditions:
a) Power parameters: Stability generated sensor signal of low voltage amplitude to a large extent depend on the quality of contact connections chain l-probe, and which should be checked first in the event of a problem;
b) intake air: l-probe design provides for the free circulation of ambient air within the sensor. When installing the probe always check the patency of air passages;
c) Working temperature: PCM starts to respond to a request by l-probe information only after the sensor is warmed up to normal operating temperature (about 320 ?� C). This fact should not be overlooked when checking serviceability of functioning of the probe;
d) Quality of fuel: The correct functioning l-probe, it is possible only if the application for vehicle refueling unleaded fuel!
In addition to those listed in the previous section, the conditions for maintenance l-probe should observe some special precautions:
a) The oxygen sensor is equipped with a tightly fitted with built-in pin connector wiring segment, the implementation attempts to disconnect that can lead to irreversible damage of the exit of the probe;
b) Try to avoid contact with the sensor or its shutters electric socket of dirt and grease;
c) Do not use an oxygen sensor for cleaning, no solvents;
d) Seek a l-probe very carefully, do not drop it, and try not to shake;
e) Silicone Protective Case should dress to the sensor in a certain way, not to be molten and not break up serviceability of functioning of the probe.
In case the serviceability of functioning l-probe or a PCM circuit becomes open-loop mode, ignoring the information coming from the sensors and supporting structure of the air-fuel mixture at a predetermined level ensuring sufficient engine efficiency impact. CHECK |
 | Oxygen sensors are extremely sensitive to the electrical circuit overload. To connect a voltmeter to the connector l-probe use fuses equipped with a jumper wire. Avoid extreme caution to enter the meter probes to the connector on the back of his hand (see chap. Onboard electric equipment). Use to test the sensor only digital gauges.
Perform the following procedure may result in a memorized OBD fault, which will be displayed control lamp "Check up the engine". Upon completion of inspection and corresponding regenerative repair do not forget to clean the system memory (see. Section System of onboard diagnostics (OBD) - a principle of functioning and codes of malfunctions). |
 | 1. Locate the sensor electrical connector. On the reverse side of the connector, connect the positive lead of the voltmeter to the terminal white wire (see chap. Onboard electric equipment). The negative probe to ground. Start the engine and warm it up to normal operating temperature. According to the testimony of the voltmeter and determine the value of the signal voltage of the sensor:
a) The amplitude of the signal generated by sensor verhnepotochnym should lie in the range from 100 to 900 mV, actively changing the limits shown.
b) Nizhnepotochny sensor must generate a voltage signal in the same range (an average of 400 mV), but no active modification. |
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2. Check the supply voltage to the sensor battery. Rate the quality of the grounding. Disconnect the sensor wiring and connect the positive lead of the voltmeter to the terminal green-black (1993 and 1994) / red-black (1995) connector (see. The wiring diagram at the end of the Head the Onboard electric equipment). The negative wire to terminal blue / blue and yellow wires. Ignition device must register the voltage close to the voltage of the battery.
3. Check the resistance of the heating element of the oxygen sensor. Connect ohmmeter to the two terminals of the heating element in the electrical connector l-probe (the part of the latter). Note: A built-in sensor wiring harness usually has no color-coding.
Required resistance is:
a) For the models 1993 and 1994 Vol. - 3.0 ÷ 1000 Ohm;
b) For the models 1995 and 1996 Vol. - 2.3 ÷ 4.3 Ohm (verhnepotochnye sensors) and 5.2 ÷ 8.2 nizhnepotochny;
c) For the models from 1997 MY. - 2.3 ÷ 4.3 Ohm.
4. In the event of termination, or at excessively high measurement results. Replace the appropriate sensor.  | At positive results the above checks should be checked for breakage and short circuit electroconducting on a chain site between the sensor and the PCM. If any deviations can not be identified, the car should be driven away on a car repair shop for more detailed diagnostics. |
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REPLACEMENT | 1. Screwing out l-probe on a cold engine can be very difficult due to the thermal contraction of the metal exhaust manifold / pipe exhaust system. To avoid the risk of damage to the components, before proceeding with the removal of the sensor warm up the engine for a couple of minutes - be careful not to burn yourself on the heated surface during the procedure:
a) Oxygen sensors are equipped with built-cable harness to the pin. Damage to harness this leads to an irreversible sensor fails - be careful;
b) Try to avoid contact with the connector and sensor shutters oil, grease, dirt, moisture, etc .;
c) in any case, do not use the sensor for cleaning any solvents;
d) Do not drop sharply and did not shake sensor.
2. Poddomkratte car and establish it on props.
3. Carefully Disconnect the oxygen sensor wiring connector.  | 4. Use the special key gently remove the probe from the relevant section of the exhaust system. |
5. Before screwing sensor lubricate threaded portion antiprihvatyvayuschim sealant.
6. Screw the sensor on the regular place and strongly tighten it.
7. Lower the car to the ground and connect the sensor wiring.
8. Make car trial runs. Check the memory of the control unit for the presence of fault codes. |
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