Def System Pressure Control

DEF pressure is maintained via feedback knowledge of sensed pressure. Pressure control is closed loop based on the voltage of the DEF pressure sensor. If a pressure increase is desired, the reductant pump motor speed is increased by increasing the PWM output. Pressure decreases are analogous; as the system has a backflow throttle, pressure will decrease to 0 unless the pump motor in run continuously. Once the set point pressure (500 kPa) is reached the following diagnostics are enabled.

REDUCTANT PRESSURE CONTROL (NORMAL) FUNCTIONAL CHECK OPERATION

DTCs	P20E8 - Reductant Pressure Too Low P20E9 - Reductant Pressure Too High
Monitor Execution	Continuous
Monitor Sequence	P20E8 & P20E9 are inhibited by active P204b, P204C or P204D codes
Sensors/Actuators OK	reductant pump pressure sensor, reductant pump motor, reductant injector
Monitoring Duration	> 10 sec (resp. > 60 sec, see below)

TYPICAL REDUCTANT PRESSURE CONTROL (NORMAL) FUNCTIONAL CHECK ENTRY CONDITIONS

Entry Condition	Minimum	Maximum
DEF system pressure in closed loop control previously	True

TYPICAL REDUCTANT PRESSURE CONTROL (NORMAL) FUNCTIONAL CHECK MALFUNCTION THRESHOLDS

P20E8: < 400 kPa for 60 sec respectively < 300 kPa for 10 sec
P20E9: > 650 kPa for 10 sec respectively > 790 kPa for 1 sec

Reductant Metering Unit Functional Check Operation

DTCs	P20FE - Reductant Metering Unit Performance P20FF - Reductant Control Module Performance
Monitor Execution	Continuous
Monitor Sequence	P007C, P007D - P20FE
Sensors/Actuators OK	CACT1 (P007C, P007D)
Monitoring Duration	P20FE - 5 sec, P20FF - continuously

TYPICAL REDUCTANT METERING UNIT FUNCTIONAL CHECK ENTRY CONDITIONS

Entry Condition	Minimum	Maximum
P20FE:
Engine Off Time	6 hrs
CAC Downstream Temperature	-20 deg C	80 deg C

TYPICAL REDUCTANT METERING UNIT FUNCTIONAL CHECK MALFUNCTION THRESHOLDS

P20FE: If difference between reductant coil temperature and CAC temperature > 20 deg C, code is set.
P20FF: Non-volatile memory corruption detected or reductant pump motor controller temperature >130 deg C

REDUCTANT PURGE CONTROL VALVE FUNCTIONAL CHECK OPERATION

DTCs	P20A0 - Reductant Purge Control Valve "A" Circuit /Open P20A2 - Reductant Purge Control Valve "A" Circuit Low P20A3 - Reductant Purge Control Valve "A" Circuit High
Monitor Execution	Continuous
Monitor Sequence	None
Sensors/Actuators OK
Monitoring Duration	Continuously

TYPICAL REDUCTANT PURGE CONTROL VALVE FUNCTIONAL CHECK MALFUNCTION THRESHOLDS

P20A0: voltage > 4.9 v
P20A2: voltage < 0.1 v
P20A3 voltage > 4.9 v

Reductant pressure is maintained via feedback knowledge of sensed pressure. A set point pressure is determined by engine operating conditions (500 kPa over exhaust backpressure). If a pressure increase is desired, the reductant pump motor speed is increased by increasing the PWM output. Pressure decreases are analogous; as the system has a backflow throttle, pressure will decrease to 0 unless the pump motor in run continuously.

DEF PUMP PRESSURE CONTROL (NORMAL) FUNCTIONAL CHECK OPERATION

DTCs	P20E8 (Reductant Pressure Too Low) P20E9 (Reductant Pressure Too high)
Monitor Execution	Continuous
Monitor Sequence	P204C and P204D must complete before setting P20E8 or P20E9
Sensors/Actuators OK	DEF pump pressure sensor, DEF pump motor, DEF injector
Monitoring Duration	> 60 sec

TYPICAL DEF PUMP PRESSURE CONTROL (NORMAL) FUNCTIONAL CHECK ENTRY CONDITIONS

Entry Condition	Minimum	Maximum
Reductant system pressurized and ready to inject

TYPICAL DEF PUMP PRESSURE CONTROL (NORMAL) FUNCTIONAL CHECK MALFUNCTION THRESHOLDS

P20E8: < 400 kPa
P20E9: > 950 kPa