4.2 Zero Fuel Quantity Calibration
P02CD, P02D5, P02D1, P02D7, P02CF, P02D3
P02CC, P02D4, P02D0, P02D6, P02CE, P02D2
General description
The injection quantity of an injector is defined by a certain energizing time at a certain rail pressure. The zero fuel quantity calibration compensates pilot injection drifts to ensure correct injection quantities over lifetime by evaluating corrections for the energizing time for each injector.
During the calibration phase (overrun, injection quantity=0), the zero fuel calibration performs pilot test injections (="zero fuel quantity") at one single cylinder. The injections cause a speed increase in the crankshaft signal which is evaluated. If the speed increase is above or below a threshold the energizing time of the calibrated injector is decreased or increased until the desired threshold is reached. The evaluated energizing time correction is filtered and written into the ECU EEPROM and so it is considered at the next engine start. This process is executed for every cylinder at several rail pressure calibration points.
If any of the evaluated energizing time corrections is above or below a threshold a preliminary DTC is stored. If this fault is detected the MIL is illuminated.
The ZFC is enabled only in warm engine conditions to ensure stable combustion of test injections.
These conditions are
- Minimum engine coolant temperature reached
- Limited uninterrupted overrun-time because of cooling down of combustion chamber
Because of noise on the crankshaft signal caused from the drive train in lower gears the ZFC is activated in gear 3 to 6 and in a defined engine speed range.
Flowchart
Scheme 79
5.1.2.4 Lambda Offset Calibration Value (P0607)
General description
To compensate the offset of the LSU signal over lifetime, an offset calibration is triggered by ECU. To detect this offset, the difference between the expected and the actual pump current is determined in the triggered operation points.
This offset of the pump current is monitored for signal range. A fault is detected and a preliminary fault code is stored, if the sensor offset voltage calibration value exceeds the upper signal range threshold or falls below the lower signal range threshold. If this fault is detected a preliminary DTC is stored. If this fault is detected in two consecutive driving cycles, the MIL is illuminated.
Flowchart
