Based on the control of the A/F sensor heater, a stabilized oxygen concentration is detected even at low exhaust temperatures, and feedback control of fuel injection even at cold engine start is made possible for improved cold temperature exhaust emission performance.
Both emission performance and sensor protection have been improved by duty control of the heater according to engine operation conditions (exhaust gas temperature).
A pre-heat has been adopted to prevent water, produced from the exhaust system when the engine is started, from adhering to the sensor and damaging it.
The A/F sensor heater is operated at a duty ratio of approx. 15% within the specified time directly after the engine is started.
The PCM operates the A/F sensor based on the following control conditions:
| Output duty ratio | Control condition |
| 0% |
|
| 0―100% (Duty ratio determined by measuring the element temperature by the A/F sensor heater element impedance) |
|