Throttle Position Sensor: Description and Operation

Throttle Valve:

Function
The throttle valve actual value potentiometers advise the position of the throttle valve (closed throttle position up to wide open throttle) to the ME-SFI control module in order to detect the various load states.

A. Ignition "Off"
In the de-energized state the position of the throttle valve is determined by the spring capsule (3).

B. Ignition "On"
When ignition is switched on, the actuator motor in the throttle valve actuator is operated by the ME-SFI control module. The throttle valve adopts a position in line with the coolant temperature.

C. Idle speed range
In the idle speed range the actuator motor controls the idle speed by opening the throttle valve more (greater mixture) or closing it more (reduced mixture), depending on coolant temperature and engine load.
In this case, the throttle valve can be closed further by the actuator motor by overcoming the force of the spring capsule (mechanical end stop).
If the actuator is de-energized, the throttle valve is resting against the spring capsule. As a result, the throttle valve opening is a constant approx. 10 - 12°. At no load, this results in an engine speed of approx. 1800 rpm.

D. Driving mode
In the driving mode (part/full load) the actuator motor controls the throttle valve in line with the various load states or in accordance with the input signals supplied by the pedal value sensor (B37) in line with the position of the accelerator pedal.


NOTE: When voltage is first connected to circuit 30, the ME-SFI control module automatically performs an adaptation of the actuator (learning lower mechanical end stop and full throttle position of throttle valve).