HINT
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that does not include cylinder No. 1.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
MONITOR DESCRIPTION
- The ECM uses information from the air fuel ratio sensor to regulate the air fuel ratio and keep it close to the stoichiometric level. This
maximizes the ability of the three way catalytic converter to purify the exhaust gases.
- The air fuel ratio sensor 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 is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage
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 will be
inaccurate, as a result, the ECM will be unable to regulate air fuel ratio properly.
- When the current in the air fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the
sensor heater and sets a DTC.
- Example:
- The ECM sets DTC P0032 or P0052 when the current in the air fuel ratio sensor heater is fail. Conversely, when the heater current is less
than 0.8 A, DTC P0031 or P0051 is set.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
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