Idle speed control

WARNING: This page is about a different car, the 2003 Saab 9-3 and 2002 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

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.