Idle speed control
| Idle speed control |
The system governs the opening of the idle speed control valve when the throttle is closed and the vehicle speed is zero so that the current idling speed corresponds with the requested. The degree of opening of the valve 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 coolant temperature. The value at -30 °C will be 1200 rpm and is gradually reduced to 900 rpm as the engine warms up.
The control module will increase the valve opening slightly when the A/C compressor starts or when DRIVE is engaged to compensate for the increase in the air required to maintain idling speed.
Changing the air flow is not fast enough to compensate for rapid changes in idling speed. For this reason, ignition control at idling speed is designed to maintain the engine speed.
The single coil idle speed control valve is powered from the main relay. The valve is controlled from control module pin 49 with a 500 Hz PWM. The valve opens more the longer the control module keeps pin 49 grounded.
If there is a break in the circuit to the idle speed control valve, the valve opening will be governed by a spring so that idling speed is at least 1000 rpm with warm engine.
| Diagnosis |
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There is no diagnosis for the electrical circuit to the idle speed control valve.
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