Feedback Control

Zero Fuel Calibration

Zero Fuel Calibration (ZFC) is an algorithm used to compensate for deviations in individual injector performance from nominal. In an overrun/decel fuel shut-off condition, fuel rail pressure is set to 300 bar and small injections are made from a single injector. The observed acceleration in crankshaft speed is detected and a regression line generated to predict the fueling required to achieve the expected acceleration. If the calculated fueling required to generate the expected acceleration in crankshaft speed falls outside the allowable control limits for the system, an addition routine is called to very precisely learn the adjustment to injector energizing time required to achieve expected acceleration. This information is then used to adjust all pilot injections on that injector to ensure correct fuel delivery. If the absolute energizing time observed for the test injection to yield the expected acceleration exceeds minimum or maximum limits, a code is set.

FBC operates in closed-loop control in an engine speed range of 500-3000 rpm, and a commanded injection quantity of 3.5 - 90 mg/stroke. The maximum allowed correction in fuel quantity for an individual cylinder is given by the following table.

ZERO FUEL CALIBRATION (ZFC) MONITOR OPERATION

DTCs	P02CC - Cylinder 1 Fuel Injector Offset Learning at Min Limit P02CD - Cylinder 1 Fuel Injector Offset Learning at Max Limit P02CE - Cylinder 2 Fuel Injector Offset Learning at Min Limit P02CF - Cylinder 2 Fuel Injector Offset Learning at Max Limit P02D0 - Cylinder 3 Fuel Injector Offset Learning at Min Limit P02D1 - Cylinder 3 Fuel Injector Offset Learning at Max Limit P02D2 - Cylinder 4 Fuel Injector Offset Learning at Min Limit P02D3 - Cylinder 4 Fuel Injector Offset Learning at Max Limit P02D4 - Cylinder 5 Fuel Injector Offset Learning at Min Limit P02D5 - Cylinder 5 Fuel Injector Offset Learning at Max Limit P02D6 - Cylinder 6 Fuel Injector Offset Learning at Min Limit P02D7 - Cylinder 6 Fuel Injector Offset Learning at Max Limit P02D8 - Cylinder 7 Fuel Injector Offset Learning at Min Limit P02D9 - Cylinder 7 Fuel Injector Offset Learning at Max Limit P02DA - Cylinder 8 Fuel Injector Offset Learning at Min Limit P02DB - Cylinder 8 Fuel Injector Offset Learning at Max Limit
Monitor Execution	Continuous
Monitor Sequence	None
Sensors OK
Typical Monitoring Duration	all DTCs 30 sec

Typical Zero Fuel Calibration (ZFC) Monitor Entry Conditions

Entry Condition	Minimum	Maximum
P02CC, P02CD, P02CE, P02CF, P02D0, P02D1, P02D2, P02D3, P02D4, P02D5, P02D6, P02D7, P02D8, P02D9, P02DA, P02DB:
Intake Air Temperature	0 deg C
Fuel Temperature	10 deg C	75 deg C
Engine Coolant Temperature	50 deg C
System Voltage	10 V
Time in overrun/decel fuel shut-off		30 sec
Engine Speed	890 rpm	1610 rpm
Boost Pressure	750 mbar
Accelerator Pedal		2%
Transmission Gear (no gear change)	4 th	6 th
Torque Converter Locked
Fuel Balance Control wheel learn complete
NOTE: these are the entry conditions for the base function. The monitor runs whenever the base function runs.

Typical Zero Fuel Calibration (ZFC) Monitor Malfunction Thresholds

P02CC, P02CE, P02D0, P02D2, P02D4, P02D6, P02D8, P02DA:
If the observed energizing time for the test injection is 156 us or more lower than the target 430 us energizing time for the given injector, the code is set.

P02CD, P02CF, P02D1, P02D3, P02D5, P02D7, P02D9, P02DB:

If the observed energizing time for the test injection is 254 us or more higher than the target 430 us energizing time for the given injector, the code is set.