Heated oxygen sensors

Heated oxygen sensors are switched on by the ECU under the following conditions:

  • – intake pressure is below a certain threshold, depending on 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 the idle position) and the temperature of the coolant.

Oxygen sensor heating is 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

The scan tool readout value for PR 138 ENGINE RATIO CORRECTION VALUE is the average value supplied by the ECU based on the mixture information provided by the oxygen sensor upstream of the catalytic converter (the oxygen sensor analyzes the oxygen content in the exhaust gas). gases).

Correction value for midpoint 50% and for end positions 0 and 100%:

  • – value below 50% request for lean mixture;
  • – value above 50% request to enrich the mixture.

Start of adjusting the composition of the working mixture

1. Phase "closed circuit control".

Adjusting the composition of the working mixture begins some time after the engine is started, if the coolant temperature is above 10 ° C (vehicles with a manual transmission) and 25 ° С (vehicles with an automatic transmission).

2. Phase "breaking the control circuit".

When adjusting 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.