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Additive adaptation

Additive adaptation



If the closed loop continually corrects a deviation in the fuel system it will be adapted. Adaptation occurs every five minutes and takes 30 seconds. The additive adaptation is always added to the fuel amount, which is 0.000 mg fuel/combustion when the control module is new or has been de-energized. The additive adaptation occurs when idling. During adaptation the purging is interrupted because no other sources affecting the fuel may be present.

The amount of fuel is added or subtracted until the closed loop value oscillates around 1.00 (0%). The reason that additive adaptation is necessary is because air leakage when idling leads to a major fault, which cannot be adapted multiplicatively since the amount of fuel would then be too great as soon as the load is increased.

The limit values for the additive adaptation are minus 5 and 5 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 so that the additive adaptation is able to occur:


• Closed loop active.

• No purging in progress; this takes place for 4 minutes and 30 seconds during each 5-minute period.

• Engine coolant temperature exceeds 78 °C.

• Engine speed 750-950 rpm.

• Engine load 85-235 mg/c.

• Car stationary.


Diagnostics


• When the additive value reaches +5 mg fuel/combustion, diagnostic trouble code P1181 will be generated.

The most probable causes are:

- Air leak after the throttle.

- Low fuel pressure.



• When the additive value reaches -5 mg fuel/combustion, diagnostic trouble code P1182 will be generated.

The most probable causes are:

- Purge valve stuck open.

- Air leak before the throttle.