SAAB WIS ONLINE

Additive adaptation

Additive adaptation



If the closed loop system continuously corrects a variation in the fuel system, it will be adapted. Adaptation takes place every five minutes and takes 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 been disconnected. The additive adaptation takes place 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 leaks occur at idling speed they 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 raised.

The limits 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 for additive adaptation to take place:


• 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 80°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 is 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 is generated.

The most probable causes are:

- Purge valve stuck open.

- Air leak before the throttle.