Monitor Description

The air fuel ratio sensor (sensor 2) detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of platinum-coated zirconia and includes an integrated heating element.

The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies this voltage generation.

The air fuel ratio sensor (sensor 2) is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful current signals without supplementary heating. The ECM regulates the supplementary heating using a duty-cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the air fuel ratio sensor (sensor 2) becomes inaccurate. As a result, the ECM is unable to regulate the air fuel ratio properly.

Air Fuel Ratio Sensor (Sensor 2) Heater Range Check (P0036-12 and P0036-13): 

1. The ECM monitors the current applied to the air fuel ratio sensor (sensor 2) heater to check the heater for malfunctions.

   If the heater current is outside the normal range, the signal transmitted by the air fuel ratio sensor (sensor 2) becomes inaccurate. When the current in the air fuel ratio sensor (sensor 2) heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

Air Fuel Ratio Sensor (Sensor 2) Heater Performance (P102A-9E): 

1. When the air fuel ratio sensor (sensor 2) heater terminal voltage is the specified value or less while the heater is not operating, the ECM determines that there is a malfunction in the sensor heater and stores DTC.