Component Description

WARNING: This page is about a different car, the 2005 Nissan Xterra. However, it is still accessible from the selected car via links, so may be relevant.

The air fuel ratio (A/F) sensor 1 is a planar dual-cell limit current sensor. The sensor element of the air fuel ratio (A/F) sensor 1 is the combination of a Nemst concentration cell (sensor cell) with an oxygen-pump cell, which transports ions. It has a heater in the element.

The sensor is capable of precise measurement "LAMPBDA" = 1, but also in the lean and rich range. Together with its control electronics, the sensor outputs a clear, continuous signal throughout a wide "LAMPBDA" range (0.7 < "LAMPBDA" < air).

Fig 1: Identifying Air Fuel Ratio (A/F) Sensor

Courtesy of NISSAN MOTOR CO., U.S.A.

The exhaust gas components diffuse through the diffusion gap at the electrode of the oxygen pump and Nemst concentration cell, where they are brought to thermodynamic balance.

An electronic circuit controls the pump current through the oxygen-pump cell so that the composition of the exhaust gas in the diffusion gap remains constant at "LAMPBDA" = 1. Therefore, the air fuel ratio (A/F) sensor 1 is able to indicate air/fuel ratio by this pumping of current. In addition, a heater is integrated in the sensor to ensure the required operating temperature of 700 - 800°C (1, 292 - 1, 472°F).

Fig 2: Air Fuel Ratio (A/F) Sensor Output Voltage Graph

Courtesy of NISSAN MOTOR CO., U.S.A.