Multiplicative adaptation
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Multiplicative adaptation
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If the closed loop system continuously corrects an irregularity in the fuel system, it will be adapted. Adaptation is carried out every five minutes and takes 30 seconds.
The fuel quantity is always multiplied by a multiplicative adaptation factor which is 1.00 when the control module is new or disconnected. Multiplicative adaptation takes place under conditions of partial load. Purging is stopped during adaptation because no other factor which can affect the fuel must be active.
The entire closed loop departure from 1.00 is added to the multiplicative adaptation factor. This means that the right fuel quantity is injected even if the closed loop is not active, e.g. during cold starting or full load running. After the engine starts, multiplicative adaptation must always take place before additive adaptation. The limits for multiplicative adaptation are 0.75 and 1.25.
The following conditions must be fulfilled for multiplicative adaptation to take place:
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The closed loop system must be active.
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No purging may occur; this takes place for 4 minutes and 30 seconds every 5-minute period. However, adaptation will be carried out immediately the first time the other conditions are fulfilled.
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Engine coolant temperature must exceed 75°C.
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Engine speed must be 1500-2750 rpm.
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The load must correspond to 175-350 mg/c.
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If the correction factor reaches 1.25 (25%), diagnostic trouble code P0171 will be generated.
The fault may have been caused by:
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Faulty mass air flow sensor.
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If the correction factor reaches 0.75 (-25%), diagnostic trouble code P0172 will be generated.
The fault may have been caused by:
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Air leakage between compressor and throttle.
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Faulty mass air flow sensor.
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