Intrusive Turbo Position And Response Monitoring

The 6.7L engine is equipped with an oil pressure actuated, variable vane turbocharger. The variable geometry turbo (VGT) does not have a position sensor, so the position is inferred using a duty cycle to position transfer function. To verify actual position based on the nominal transfer function, an intrusive monitor sweep is performed. When entry conditions are met, the intrusive monitor for VGT closes the EGR valve, opens the throttle and then commands the output PWM to open and closed position for a calibratable duration. Typical values are 85%, then 25%. The minimum and maximum MAP values are saved and compared to a threshold. If the desired separation in MAP pressure isn't achieved, a fault is detected. If the desired separation in MAP is achieved, the test is considered a pass.

Courtesy of FORD MOTOR CO.

In the example above, at 1871 seconds, the EGR valve is commanded closed, after 3 seconds with EGR off and turbocharger at 85% position, the turbocharger is opened up to. 25% position. The 25% position is held for 4 seconds. If desired separation of 2 kpa at sea level is achieved the test is considered a pass. If desired separation isn't achieved the test is completed and failed.

NOTE: This monitor also serves to monitor for a slowly responding boost pressure system due to the time component of the threshold.

NOTE: On 3.2L engine, there is variable geometry turbo control and position.

VGT MONITOR

DTCs	P132B - Turbocharger/Supercharger Boost Control "A" Performance
Monitor Execution	Once per driving cycle
Sensors OK	ECT, MAP, VS, VGTP
Typical Monitoring Duration	7 seconds for full VGT monitoring cycle if pressure abort threshold hasn't been reached

TYPICAL VGT MONITOR ENTRY CONDITIONS

Entry Condition	Minimum	Maximum
Engine speed for learning	500 rpm	760 rpm
Pedal position allowed for learning		0.5%
Engine coolant temperature for learning	70 deg C	124 deg C
Fuel quantity allowed for learning		20 mg/stoke
Vehicle speed for learning		3 mph
Time at idle	5 sec
Barometric Pressure	67 kPa	102 Kpa
Time after engine start	120 seconds
Battery voltage	10V	16V
Engine operating mode	Normal (no post injection)

TYPICAL VGT MONITOR MALFUNCTION THRESHOLDS

Response from 25% VGT position to 85% VGT position in 4 seconds results in a change in manifold pressure of 2 kPa or greater at sea level or 1.25 kPa at 8000 feet.