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Other air request

Other air request





Idle speed control

When the accelerator is completely released and the vehicle speed is zero, the system will then govern the air mass/combustion necessary to make the current idling speed correspond with the requested. The air requirement is stored in the control module memory (adaptation). The requested idling speed is stored in a table in the control module memory and depends on the engine coolant temperature.

The value is 1200 rpm at -30°C and the requested engine speed gradually drops to 825 rpm as the engine warms up.

TCM sends bus information "Selector lever position”, unit P, R, N, D, 3, 2 or 1. The value is used by Trionic T7.

When any value other than P or N is selected, the requested air mass/combustion is increased to compensate for the impending increase in load. This is to fully compensate for the increased engine torque requirement of the automatic transmission so that a rapid decrease of the idling speed is avoided before the idle speed control has time to compensate. The air requirement in any other position than P or N is stored in the control module memory (adaptation).



As soon as the car is in motion, the idle speed control is disengaged and the engine receives the adapted air quantity.

Diagnostics


• If the idling speed is too high, diagnostic trouble code P0507 will be generated.

If the idling speed is too low, diagnostic trouble code P0506 will be generated.

• The difference between the requested idling speed and the current idling speed can be read with the diagnostic tool, as can whether idle speed control is active.