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Additive adaptation

Additive adaptation

If the closed loop continuously corrects a variation in the fuel system it will then become adapted. Adaptation takes place every five minutes and lasts for 30 seconds. The fuel quantity is always added by an additive adaptation factor, which is 0.000 mg fuel/combustion when the control module is new or disconnected. The additive adaptation occurs while idling. Purging is stopped during adaptation because no other factor that can affect the fuel must be active.

The fuel quantity is added or subtracted until the closed loop value fluctuates around 1.00 (0%). The reason additive adaptation is required, is that when air leakage occurs on idling it can lead to a major fault that must not be adapted multiplicatively, because the fuel quantity would then be too great as soon as the load is increased.

The limits for the additive adaptation are minus 4 and 4 mg fuel/combustion respectively.

After the engine has been started a multiplicative adaptation must always occur before an additive adaptation.

The following conditions must be fulfilled for additive adaptation to take place:




• Closed loop active.

• No purging may occur; this takes place for 4 minutes and 30 seconds every 5-minute period.

• Engine coolant temperature exceeds 75°C.

• Engine speed 750-950 rpm.

• Engine load 90-200 mg/c.

• Car stationary.


Diagnostics


• When the additive value reaches +4 mg fuel/combustion diagnostic trouble code P1181 is generated.

The most probable cause of the fault is:

- Air leakage after the throttle.

- Low fuel pressure.



• When the additive value reaches -4 mg fuel/combustion diagnostic trouble code P1182 is generated.

The most probable cause of the fault is:

- The purge valve has jammed in the open position.

- Air leakage before the throttle.