Throttle Plate - PFI: Description and Operation

Throttle actuator
The electromotive throttle actuator is secured to the intake plenum.

A throttle valve is necessary for all diesel engines equipped with a particulate filter system. The throttle valve chokes the intake air to ensure that the necessary increased exhaust-gas temperatures required for regeneration of the particulate filter are reached.

The throttle-valve actuator closes when the engine is switched off. This counteracts the engine's tendency to vibrate during the shutdown phase.

Yet another function is preventing the engine from overrevving. When the DDE Digital Diesel Electronics system detects increases in engine speed although no corresponding rises in the injection quantity have occurred, it responds by closing the throttle valve to limit engine speed.

Functional description
The DDE control unit opens and closes the throttle valve actuator electrically. The throttle valve's precise current position must be registered at all times to as a condition for optimal control. This function is discharged by the throttle-valve sensor, which provides contactless monitoring of the throttle valve's position within the throttle-valve actuator.







When no power is being applied spring force holds the throttle valve open within the throttle-valve actuator.

Structure and inner electrical connection
The servo-motor employed to adjust the position of the throttle valve is a DC motor. The throttle-valve sensor is a Hall-effect device. The hall effect sensor determines the revolutions of the servomotor. This provides the basis for calculating the position of the throttle valve.







Signal shape and set point values
The DDE furnishes the 5-volt power and the earth connection for the throttle-valve actuator.

A bridge circuit (H bridge) is used to activate the servomotor. This permits activation of the servomotor in the opposite direction. Diagnostic technology monitors the bridge circuit. The H-bridge is an electrical circuit in which 5 switching elements are linked in the form of a capital letter H.







Please note the following specifications for the throttle-valve actuator:

Size Value
Servomotor supply voltage 12 Volts
Activation frequency for 1300 Hz
servomotor
Blocking current for servomotor 4 A
Electrical power supply for 4.5 to 5.5 V
throttle-valve sensor
Current draw of throttle-valve 10 mA
sensor
Operating temperature range for -40 °C to 140 °C
throttle-valve sensor and
servo-motor

Diagnosis instructions

Failure of the component
Should the throttle-valve sensor fail the following symptoms can be expected:
- Fault entry in the engine control unit
- Emergency operation with substitute value (limited engine torque)
- Check Control message

If the servomotor fails, the following behavior is to be expected:
- Fault entry in the engine control unit
- The throttle-valve assumes its mechanical emergency-air position
- Check Control message

We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.