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Additive adaptation

Additive adaptation





If closed loop continuously corrects a deviation in the fuel system, it will be adapted. Adaptation occurs every 5 minutes and takes 30 seconds. An additive adaptation factor that is 0.000 mg fuel/combustion when the control module is new or has been de-energized is always added to the fuel quantity. The additive adaptation takes place at idling speed. Purging is interrupted during adaptation as no other sources affecting the fuel may be present.

The fuel quantity is added or subtracted until the closed loop value fluctuates around 1.00 (0%). Additive adaptation is required because an air leak at idling speed would lead to a major fault that must not be adapted multiplicatively, since the fuel quantity would be far too large once the load had increased.

Limits for additive adaptation are minus 4 and 4 mg fuel/combustion respectively.

After the engine has been started, a multiplicative adaptation must take place before an additive.

The following conditions must be fulfilled before an additive adaptation can be carried out:


• 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 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 will be generated.

The most probable causes are:

- Air leak after the throttle.

- Low fuel pressure.



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

The most probable causes are:

- Purge valve stuck open.

- Air leak before the throttle.