Heated sensors
Heated oxygen sensors are switched on by the command of 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 a certain time of engine operation according to the program, depending on TDC (without taking into account the operating time with the accelerator pedal released) and coolant temperature.
Oxygen sensor heating stops:
- if the vehicle speed is over 140 km/h (reference value),
- under heavy engine load.
Upper sensor signal voltage
Read parameter value: «upper sensor signal voltage» on the scan tool: this is the amount of voltage that is sent to the computer by the oxygen sensor upstream of the catalytic converter. The voltage value is expressed in millivolts. When the motor is running in closed loop, the voltage should fluctuate rapidly between two values:
- 100 mV±100 lean;
- 800 mV±100 for a rich operating mixture.
The smaller the difference between the minimum and maximum values. the less accurate the information from the sensor (usually this difference is at least 500 mV).
Note. If this difference is small, check the sensor heating.
Lower sensor signal voltage
It is necessary to read the parameter value: «lower sensor signal voltage» on the diagnostic tool. This is the amount of voltage that is transmitted to the ECU by the oxygen sensor installed after the catalytic converter. The voltage value is expressed in millivolts.
This sensor is designed to diagnose the catalytic converter and repeat, more accurate, control of the composition of the mixture (slow control loop). This function is activated only after the engine has been running for a while.
When the motor is running in closed loop, the voltage should change in the range of 600 mV±100. When the speed decreases, the voltage should be below 200 mV.
Do not take into account the voltage value read from the scan tool at idle.
Correction of the composition of the working mixture
Parameter value «correction of the composition of the working mixture», scan tool readout is an average value provided by the ECU based on the mixture information provided by the oxygen sensor upstream of the catalytic converter (in fact, the oxygen sensor analyzes the oxygen content in the exhaust gases).
The average value of the correction is 128, and the extreme ones are 0 and 225.
Value below 128: lean request.
Value greater than 128: enrichment request.
Commencement of fuel mixture regulation
Phase «closing the control loop»
The regulation of the composition of the working mixture begins after a time delay after starting the engine no more than 0 s. if the coolant temperature is above 0 *C for the F4P engine and Yu'C for the K4M engine.
Phase «control loop opening»
When adjusting the composition of the working mixture, the ECU does not take into account the voltage value of the sensor signal 8 in the following cases:
- when you press the accelerator pedal all the way;
- during hard acceleration:
- when decelerating, if there is information about the released accelerator pedal;
- when the oxygen sensor fails.
Standby mode in case of failure of the oxygen sensor
If the signal voltage of the oxygen sensor during the regulation of the composition of the working mixture is incorrect (changes very little or not at all), then the ECU will only go into standby mode if the fault has been declared present for 3 minutes. Only in this case, information about the malfunction will be entered into the memory of the computer. In this case, the parameter value «correction of the composition of the working mixture» equals 128.
If an oxygen sensor malfunction is detected, if information about the malfunction is already stored in the memory, the ECU immediately switches the engine to work with an open control loop.