Engine Idle Speed Control

Engine Idle Speed Control

The ATC (automatic temperature control) module signals the ECM (engine control module) to increase engine idle speed settings if a high current application is switched on or if low battery voltage is detected. The signal consists of a message transmitted via the K bus, instrument cluster and high speed CAN (controller area network) bus, and increases idle speed between 100 and 200 rev/min. The ATC (automatic temperature control) module requests the engine idle speed increase when the following high current applications are switched on:
^ HRW.
^ Blower, at speed 6 or 7.
^ Headlamp main beam.

The engine idle speed increase is also requested if battery voltage decreases to less than 11.4 V. The speed increase request is discontinued when battery voltage increases to more than 12.2 V again.