WHAT DOES IT DO?

The heated oxygen sensor in the Skylines is used to measure the amount of oxygen in the exhaust gases, and sends this information to the ECU to assist in adjusting the air-fuel mixture to ensure correct emissions are output and also to maximise fuel economy.

	What does it look like? - R33 Series II RB25DET Oxygen Sensor

HOW DOES IT WORK?

The oxygen sensor has oxygen-ion conductive ceramic material in the tip of the device. Once the tip is over ~300 degrees Celsius, the atmospheric oxygen levels (measured through a vent in the sensor to the atmosphere) are compared to the oxygen levels in the exhaust gas, and a voltage generated proportional to the difference between the oxygen levels.

The output voltage should vary between 0.1 volt (lean) to 1.0 volt (rich) once the sensor has reached its operating temperature of above 300 degrees Celsius.

Skylines use a heated 3-wire sensor which offer better start and cold running performance and more stable hot running performance. The three wires are:

• Supply for heater element (12v)
• Oxygen sense (0.1 to 1.0v)
• Earth return (0v)

WHAT ARE THE SYMPTOMS FOR WEAR OR FAILURE?

A faulty oxygen sensor can generate some of the following symptoms:

• Poor fuel economy
• Failure of emissions tests
• Drive-ability problems including surging
• Unburned fuel being visible as smoke/vapour from exhaust under heavy acceleration

HOW IS IT MAINTAINED?

The oxygen sensor cannot be maintained or repaired. Once the sensor no longer functions, it should be replaced. Nissan recommends an inspection and replace if necessary every 40,000 km (24,000 Miles). Repco recommends it should be replaced at 50,000 km (30,000 Miles)

HOW CAN IT BE TESTED?

The sensor should be checked using an oscilloscope, however it can also be tested using a digital multimeter for a go/no go comparison.

The engine should be warmed up first so that the exhaust is at standard operating temperature. Do not disconnect the sensor during testing. Connect test lead to read the voltage from the sense line. Measurements are referenced to 0 volts (Ground).

Test using oscilloscope

• Set time base to 500mS per division and vertical to 0.2 volts per division (x1 probe).
• Connect probe to sense line.
• Maintain engine rpm at approximately 2000 rpm.
• A correctly operating sensor will indicate a fluctuating voltage of approximately 0.2 to 0.8 volts. The lean-to-rich and rich-to-lean response times should be less than 300mS. Anything slower than this will indicate that the sensor should be replaced.

Test using digital multimeter

• Set digital multimeter to 2 volts DC range.
• Connect probe to sense line.
• With engine at idle, give a small increase in throttle and return to idle.
• A correctly operating sensor will indicate a fluctuating voltage of approximately 0.1 to 0.6 volts. Beware that it is not possible to measure the response time using this method so a fluctuating voltage does not necessarily mean the sensor is working. The only thing that can be determined is that if there is no fluctuation in voltage, then the sensor is faulty and should be replaced.

WHERE IS IT LOCATED?

In the exhaust between the manifold and the catalytic converter.

	What does it look like?

WHAT IS THE PART NUMBER AND COST?

R33 Series II RB25DET Oxygen Sensor

• Part number on the body of the sensor reads BOSCH A24-A21 139 6X171
• Nissan part number ???
• Cost NZ$250+ ???