Heated sensors
Heated oxygen sensors are switched on by the ECU under the following conditions:
- the intake pressure is below a certain threshold, depending on the engine speed;
- speed below 135 km/h;
- after the engine has been running for some time, determined depending on the TDC of the engine pistons (if the accelerator pedal is not in position «idling») and coolant temperature.
Heated oxygen sensors are disabled when the following conditions are met:
- vehicle speed above 140 km/h (reference value);
- high engine load.
Correction of the composition of the working mixture
Value of parameter PR 138 read on the diagnostic tool «MIXTURE CORRECTION VALUE» represents the average value introduced by the ECU depending on the information about the composition of the working mixture transmitted by the oxygen sensor installed before the catalytic converter (oxygen sensor analyzes the oxygen content in the exhaust gases).
Correction value for midpoint 50% and for end positions 0 and 100%:
- value below 50% lean request;
- value above 50% request for enrichment of the mixture.
The beginning of the regulation of the composition of the working mixture
1. Phase «closed loop regulation».
The regulation of the composition of the working mixture begins some time after the engine is started, if the temperature of the coolant is above 10°C (vehicles with manual transmission) and 25°С (vehicles with automatic transmission).
2. Phase «control circuit opening».
When regulating the composition of the fuel mixture, the ECU does not take into account the voltage value of the sensor signal in the following cases:
- when you press the accelerator pedal all the way;
- with significant loads and high crankshaft speed;
- when decelerating, if there is information about the released accelerator pedal;
- when the oxygen sensor fails.