Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Air mass control, basic function: Notes
- Driver requestÂ
The control module reads pedal potentiometer 1 and converts the voltage to air mass/combustion (mg/c). The value is sent to box 3.
- Cruise control requestÂ
When cruise control is active, the air mass/combustion required to maintain the set speed is calculated. The value is sent to box 3.
- Select highest valueÂ
The control module selects the highest of the two values. The value is sent to box 5.
- Engine torque limitationÂ
Maximum permissible air mass/combustion varies depending on the engine variant. During operation, the maximum permissible air mass/combustion must also be limited to protect the engine, gearbox, brakes or turbo.
External units, such as the automatic transmission, can also limit the maximum permissible air mass/combustion. Limitation can also take place in case of a system fault. The control module selects the lowest value. The value is sent to box 5.
- Select lowest valueÂ
The control module selects the lowest value and sends it to box 8.
- Compensation requestÂ
When the A/C compressor is on, and when the electrically heated rear window or radiator fan is on, the air mass/combustion required to compensate for the increased load is calculated. The value is sent to box 8.
- OTHER AIR REQUESTÂ Â
The control module calculates the air mass/combustion required for idle speed control. The value is sent to box 8.
- Totalling valuesÂ
The control module total all the values. The total is sent to box 9.
- Total system air requestÂ
This value is the total system air request. The value is sent to box 10.
- Throttle controlÂ
The requested air mass/combustion is converted to requested voltage for throttle position sensor 1. The charge air pressure and intake air temperature are used to correct this conversion. The throttle motor rotates the throttle until the current voltage for throttle position sensor 1 corresponds with the requested voltage.
NOTE: The system regulates the current air mass/combustion so that it corresponds with the requested value. It is completely normal for the throttle not to be fully open despite the accelerator pedal being fully depressed. - Current air mass/combustionÂ
The requested air mass/combustion is also compared with the current air mass/combustion (current MAF value/combustion). If necessary, the requested voltage for throttle sensor 1 is finely adjusted.
- Turbo controlÂ
If the requested air mass/combustion is too high to be handled by the throttle control alone, the turbo control will take over. The excess is converted to a PWM, which controls the charge air control valve. The absolute atmospheric pressure is used to correct this conversion.
- Current air mass/combustionÂ
The requested air mass/combustion is compared with the current air mass/combustion and the charge air control valve PWM is finely adjusted if necessary.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.