Multiplicative adaptation
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Multiplicative adaptation
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If closed loop continuously corrects a deviation in the fuel system, it will be adapted. Adaptation occurs every five minutes and takes 30 seconds.
The fuel quantity is always multiplied by a multiplicative adaptation factor that is 1.00 when the control module is new or has been de-energized. The multiplicative adaptation takes place during partial load. Purging is interrupted during adaptation as no other sources affecting the fuel may be present.
The entire closed loop deviation from 1.00 is transferred to the multiplicative adaptation factor. This ensures that the correct fuel quantity is injected even when closed loop is not active, such as when cold starting or driving with a full load. After starting the engine, a multiplicative adaptation must take place before an additive. Limits for the multiplicative adaptation are 0.75 and 1.25 respectively.
The following conditions must be fulfilled before multiplicative adaptation can take place:
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Closed loop must be active.
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No purging in progress; this takes place for 4 minutes and 30 seconds during each 5-minute period. However, an adaptation will take place directly the first time the other conditions have been 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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Engine load must be the equivalent of 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 can be caused by:
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Defective 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 can be caused by:
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Air leak between the compressor and the throttle.
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Defective mass air flow sensor.
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