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.