### Oxygen Sensor

#### INSPECTION AND REPLACEMENT

Fig. 1: Oxygen sensor location — 200SX

Fig. 2: Exhaust gas sensor testing procedure

An exhaust gas sensor warning light will illuminate on the instrument panel when the car has reached 30,000 miles This is a signal that the oxygen sensor must be replaced. It is important to replace the oxygen sensor every 30,000 miles, to ensure proper monitoring and control of the engine air/fuel mixture. Refer to "Maintenance Reminder Lights'' section.

The following service procedure is recommend by Nissan Motor Company for all models to 1987 year, after this point complete Engine Self-Diagnosis is necessary. The oxygen sensor can be inspected using the following procedure:

1. Start the engine and allow it to reach normal operating temperature.
2. Run the engine at approximately 2,000 rpm under no load. Block the front wheels and set the parking brake.
3. An inspection lamp has been provided on the bottom of the control unit, which is located in the passenger compartment (refer to the illustrations for location of control unit). If the oxygen sensor is operating correctly, the inspection lamp will go on and off more than 9 times in 10 seconds. The inspection lamp can be more easily seen with the aid of a mirror.
4. If the lamp does not go on and off as specified, the system is not operating correctly. Check the battery, ignition system, engine oil and coolant levels, all fuses, the fuel injection wiring harness connectors, all vacuum hoses, the oil filler cap and dipstick for proper seating, and the valve clearance and engine compression. If all of these parts are in good order, and the inspection lamp still does not go on and off at least 9 times in 10 seconds the oxygen sensor is probably faulty. However, the possibility exists that the malfunction could be in the fuel injection control unit. The system should be tested by a qualified technician (ASE certified) with specific training in the "Mixture Ratio Feedback System''.

   To replace the oxygen sensor:

5. Disconnect the negative battery cable and the sensor electrical lead. Unscrew the sensor from the exhaust manifold.
6. Coat the threads of the replacement sensor with a nickel base anti-seize compound. Do not use other types of compounds, since they may electrically insulate the sensor. Do not get compound on sensor housing. Install the sensor into the manifold. On models through 1987, installation torque for the sensor is 18–25 ft. lbs.; on 1988 and later models, torque is 30–37 ft. lbs. (Note, the 1987 200SX model oxygen sensor torque is also 30–37 ft. lbs.) Connect the electrical lead. Be careful handling the electrical lead. It is easily damaged.
7. Reconnect the battery cable.

   NOTE: The oxygen sensor is installed in the exhaust manifold and is removed in the same manner as a spark plug. Exercise care when handling the sensor do not drop or handle the sensor roughly. Care should be used not to get compound on the sensor itself.