PEC idle speed control function

S07.52-3011-06

Task

 Controlling idle speed at different engine loads (e.g. power steering at full lock, gear engaged, AC compressor switched on).

Function

The idle speed control actuator (M33) controls the idle speed by altering the position of the throttle valve. It is actuated by the PEC control module (A13).

Design

A13 PEC control module

B60 Coolant temperature sensor

B73 Crankshaft position sensor

M33 Idle speed control actuator

S75 Starter lockout switch (if code G40 automatic transmission fitted)

Heating-up speed

Engine speed is increased for a certain time at low coolant temperatures each time the engine is started in order to more rapidly warm up the catalytic converter to its operating temperature. The engine speed increase is immediately canceled if a gear is engaged.

Idle seed

The ignition angle is slightly retarded or advanced from the computed specified speed in order to assist the idle speed control.



Altering the ignition angle provides more rapid control than altering the position of the throttle valve.

Engines with automatic transmission

When a gear is engaged, a lower engine speed is controlled in order to reduce the tendency of the vehicle to creep. The information "gear engaged/not engaged" is supplied by the starter lockout switch (S75) to the PEC control module (A13).

Engines with AC compressor

To avoid engine speed dropping in the idle speed range when the AC compressor is engaged, the AC control module (A13) before the AC compressor is engaged. As a result, the idle speed control actuator (M33) enlarges the opening cross-section of the throttle valve.