Oxygen Sensor Heating
Oxygen sensor heating is activated by the ECU when the following conditions are met:
- – intake pressure is below a certain threshold depending on engine speed;
- – vehicle speed is below 135 km/h;
- – after the engine has been running for a certain period of time, determined depending on the TDC of the engine cylinders (if the accelerator pedal is not in the idle position) and the coolant temperature.
Oxygen sensor heating is deactivated when the following conditions are met:
- – vehicle speed is above 140 km/h (reference value);
- – high engine load.
Fuel Mixture Composition Correction
The value of parameter PR 138 "FUEL MIXTURE COMPOSITION CORRECTION VALUE" read on the diagnostic tool represents an average value entered by the ECU depending on the information about the fuel mixture composition transmitted by the oxygen sensor installed upstream of the catalytic converter (the oxygen sensor analyzes the oxygen content in the exhaust gases).
The correction value is 50% for the midpoint and 0 and 100% for the extreme positions:
- – a value below 50% indicates a request for a leaner mixture;
- – a value above 50% indicates a request for a richer mixture.
Start of Fuel Mixture Composition Control
1. Closed-loop control phase.
Fuel mixture composition control begins some time after the engine is started, if the coolant temperature is above 10°C (vehicles with a manual transmission) and 25°C (vehicles with an automatic transmission).
2. Open-loop control phase.
When regulating the fuel mixture composition, the ECU does not take into account the sensor signal voltage value in the following cases:
- – when the accelerator pedal is fully depressed;
- – under significant loads and high crankshaft rotational speed;
- – during deceleration, if there is information that the accelerator pedal has been released;
- – in the event of an oxygen sensor failure.
