Suzuki Samurai/Sidekick/Tracker 1986-1998 Repair Guide

Oxygen Sensor

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OPERATION



The 1996-98 1.6L MFI and 1.8L engines are equipped with two Heated Oxygen Sensors (HO2S): HO2S 1 is mounted in the exhaust manifold, HO2S 2 is mounted in the exhaust system after the catalytic converter.

The Oxygen Sensor (O2S) is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gases. Starting in 1991, electrically-heated oxygen sensors were used. Heated Oxygen Sensors (HO2S) reach operating temperature sooner, which allows earlier activation of the closed loop fuel control.

The O2S has the ability to produce a low voltage signal that feeds the information on the engine's exhaust content to the Engine Control Module (ECM). The O2S is constructed from a material (zirconium/platinum) that conducts electricity under certain conditions. At operating temperature (600°F/315°C), the element becomes a semiconductor. A platinum coating on the outer surface of the element stimulates further combustion of the exhaust gases right at the surface, which keeps sensor heated to the proper temperature. The O2S is constructed with an inner cavity, which is filled with atmospheric (reference) air. The atmosphere is composed of approximately 21% oxygen. In this electrical circuit, the inner cavity is the positive terminal. The outer surface of the sensor is exposed to the exhaust gas stream, and is the negative (ground) terminal. The oxygen concentration difference between the reference air and the exhaust gases produces a small voltage signal.

All oxygen sensors operate in the same manner. The voltage ranges differ from approximately 0.1 volt (high O2/lean mixture) to 0.9 volt (low O2/rich mixture). The voltages are monitored and used by the ECM to fine tune the air/fuel ratio mixture to achieve the ideal mixture desired. The ECM sends a reference signal of 450 millivolts. This reference serves to run the engine when it is in open loop mode of operation. When the air/fuel ratio is correct, the ECM will display 450 millivolts. When the engine is operating with a rich air/fuel mixture, there is a reduction of free oxygen in the exhaust stream and the oxygen voltage rises above the reference signal. When the engine is running lean, the voltage drops below the reference voltage due to excess oxygen in the exhaust gases. The 02S provides the feedback information for the closed loop operating mode of the fuel delivery system.

The oxygen sensor is located on the left-hand side of the engine, mounted in the upper side of the exhaust manifold.

TESTING



1.3L Carbureted Engine
  1. Perform a visual inspection of the connector to ensure that it is properly connected and all terminals are straight, tight and free from corrosion or damage.
  2.  
  3. Start the engine and allow it to reach normal operating temperature.
  4.  
  5. Detach the oxygen sensor connector from the wiring harness.
  6.  
  7. Set a Digital Volt-Ohmmeter (DVOM) to the voltmeter setting, then attach the positive lead to the oxygen sensor terminal and the ground lead to a good engine ground. Be sure to use a digital voltmeter, otherwise an inaccurate reading may occur.
  8.  


WARNING
Never apply voltage to the oxygen sensor, otherwise it may be damaged. Also, never connect an ohmmeter (or a DVOM set on the ohm function) to the oxygen sensor; it will damage the sensor.

  1. Run the engine at 1500-2000 rpm and turn the wide open micro-switch OFF by moving the lever with your finger. Measure the voltage of the oxygen sensor with the DVOM; the value should be approximately 0.8 volt.
  2.  
  3. Run the engine between 1000-1500 rpm and disconnect the Mixture Control Valve (MCV) solenoid vacuum hose from the intake manifold. Check the voltage of the oxygen sensor again, and ensure that it is below 0.2 volt.
  4.  
  5. If the oxygen sensor did not function as noted, replace it with a new one.
  6.  
  7. When done inspecting the oxygen sensor, reconnect the MCV solenoid vacuum hose to the intake manifold.
  8.  

1.3L and 1.6L TFI Engines

Before performing the oxygen sensor test procedures, ensure that the following items are in good working order:



The air cleaner is not clogged.
 
There are no vacuum leaks.
 
The spark plugs are in good condition.
 
The spark plug wires are in good condition.
 
The distributor cap and rotor are in good condition.
 
The ignition timing is correct.
 
Engine compression is satisfactory.
 

If a Diagnostic Trouble Code (DTC) No. 13 and another code are indicated together, the latter code takes priority over Code No. 13. Therefore, check and correct any other DTC components indicated by the ECM first, then perform the following tests.

PERFORMANCE TEST

CAUTION
When performing this procedure, be sure to keep out of the way of moving or hot engine components. Refrain from wearing loose clothing.

  1. Perform a visual inspection of the connector to ensure that it is properly connected and all terminals are straight, tight and free from corrosion or damage.
  2.  
  3. Start the engine and allow the engine to reach normal operating temperature.
  4.  
  5. Run the engine at 2000 rpm.
  6.  
  7. Detach the wiring harness connector from the O2 sensor.
  8.  
  9. Measure the voltage between the terminal on the sensor and a good ground (a metal part of the engine). The sensor voltage should fluctuate between 0-900 millivolts.
    1. If the voltage does not fluctuate, or reads 0 millivolts, replace the O2 sensor.
    2.  
    3. If the voltage does not fluctuate between 0-450 millivolts, skip to the next step.
    4.  

  10.  
  11. Observe the voltmeter and remove the MAP sensor vacuum line. The O2 sensor voltage should jump to 900 millivolts.
    1. If the voltage does not fluctuate between 0-450 millivolts, or jump to 900 millivolts, replace the O2 sensor.
    2.  
    3. If the voltage increases to 900 millivolts, the O2 sensor is functioning properly.
    4.  

  12.  

HEATING ELEMENT TEST

This test only applies to 1991 and later models; earlier models do not utilize an electrically-heated oxygen sensor.

  1. If the engine is warm, allow it to cool down.
  2.  
  3. Turn the ignition switch OFF .
  4.  
  5. Detach the wiring harness connector from the oxygen sensor.
  6.  
  7. Connect a Digital Volt-Ohmmeter (DVOM), set on the ohmmeter function, to the two heating element terminals of the oxygen sensor.
  8.  
  9. Measure the resistance of the heating circuit in the sensor. The resistance should be between 3.0-5.5 ohms at 68°F (20°C).
    1. If the ohm values are within specifications, the heating element if functioning properly.
    2.  
    3. If the ohm readings are not within the specified range, replace the HO2 sensor with a new one.
    4.  

  10.  

1.6L MFI Engine

  1. Perform a visual inspection of the connector to ensure that it is properly connected and all terminals are straight, tight and free from corrosion or damage.
  2.  
  3. Detach the wiring harness connector from the oxygen sensor, and check the resistance between terminals 1 and 4 of the sensor. Resistance should be between 10-15 ohms at 70°F (21°C). If the resistance is not within the specified range, replace the oxygen sensor with a new one.
  4.  
  5. If the resistance was within specification, check for battery (B+) between the wiring harness connector terminals 1 and 4 with the ignition switch ON . If battery positive voltage is not present at the connector, check oxygen sensor circuit continuity back to the ECM. If the circuits are good, the ECM may be defective.
  6.  
  7. Check the sensor voltage between terminal 2 and the sensor body with the ignition switch OFF . Voltage should be between 30-500 millivolts. If the voltage is not within specification, replace the sensor with a new one.
  8.  
  9. If the voltage was as specified, recheck the voltage after heating the engine to normal operating temperature. With the engine running at 1200 rpm, the sensor voltage should vary between 100-900 millivolts. If the voltage does not fluctuate, or is not within the specified range, replace the sensor with a new one.
  10.  
  11. If the voltage was within the specified range, check the oxygen sensor circuits back to the ECM. If the sensor and circuits are functional, the ECM is most likely defective.
  12.  

1.8L Engine

See Figure 1

  1. Start the engine and allow it to warm up to normal operating temperature.
  2.  
  3. Run the engine at 2000 rpm for at least 2 minutes.
  4.  
  5. Turn the ignition switch OFF , then disengage the wiring harness connector from the oxygen sensor.
  6.  
  7. Connect a Digital Volt-Ohmmeter (DVOM), set on the voltmeter function, to terminals 1 and 2 of the oxygen sensor.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Use a DVOM set on the voltmeter function to measure the oxygen sensor output voltage

  1. Start the engine and have an assistant repeatedly rev the engine while you observe the voltmeter. The oxygen sensor voltage should fluctuate from below 0.5 volt to above 0.5 volt.
  2.  
  3. If the oxygen sensor voltage never rises above 0.5 volt or falls below 0.5 volt, it is defective and should be replaced.
  4.  
  5. If the voltage does fluctuate between leff than 0.5 volt and greater than 0.5 volt, there is a defect in the wiring circuit. Inspect all connectors for a tight fit, the ECM for a malfunction, and the circuit for an open or poor connection.
  6.  

REMOVAL & INSTALLATION



See Figures 2 and 3

The 1996-98 1.6L MFI and 1.8L engines are equipped with two heated oxygen sensors: HO2S 1, mounted in the exhaust manifold, and HO2S 2, mounted in the exhaust system after the catalytic converter.

The oxygen sensor uses a permanently attached pigtail and connector. The pigtail should not be removed from the sensor. Damage or removal of the pigtail or connector could affect proper operation of the oxygen sensor.


WARNING
Take care when handling the oxygen sensor. The inline electrical connector and louvered end of the sensor must be kept free of grease, dirt or other contaminants. Also, avoid using cleaning solvents of any type on the sensor.

  1. Run the engine until it has warmed up to normal operating temperature.
  2.  
  3. If removing HO2S 2, raise and securely support the front of the vehicle on jackstands. Apply the parking brake and block the rear wheels.
  4.  



Click image to see an enlarged view

Fig. Fig. 2: All models are equipped with an oxygen sensor mounted in the exhaust manifold ...



Click image to see an enlarged view

Fig. Fig. 3: ... but the 1996-98 engines are equipped with a second oxygen sensor, mounted in the exhaust pipe after the catalytic converter


CAUTION
Be cautious when working on and around the hot exhaust system. Painful burns will result if naked skin is exposed to the exhaust system pipes or manifold.

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the wiring harness connector from the sensor connector.
  4.  


WARNING
The oxygen sensor may be difficult to remove when the engine temperature is below 120°F (48°C). Excessive force may damage the threads in the exhaust manifold or pipe.

  1. Carefully remove the oxygen sensor from the exhaust manifold or pipe. If may be necessary to use a socket that is designed specifically for this purpose.
  2.  

See Figures 4 through 6



Click image to see an enlarged view

Fig. Fig. 4: Using a flare nut wrench ...



Click image to see an enlarged view

Fig. Fig. 5: ... loosen the oxygen sensor from the manifold or exhaust pipe



Click image to see an enlarged view

Fig. Fig. 6: Remove the sensor, being careful not to damage the sensor tip

To install:

A special anti-seize compound is used on the oxygen sensor threads. The compound consists of a liquid graphite and glass beads. The graphite will burn away, but the glass beads will remain, making it easier to remove the sensor. New sensors will already have the compound applied to the threads. If a sensor is removed from an engine and is to be reinstalled, the threads must have an anti-seize compound applies prior to installation.

  1. Thread the sensor into the exhaust manifold or pipe, and tighten it to 29-36 ft. lbs. (40-50 Nm).
  2.  
  3. Reattach the wiring harness to the sensor connector.
  4.  
  5. If necessary, lower the vehicle and remove the rear wheel blocks.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. Start the engine and verify proper sensor operation.
  10.  

 
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