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System overview, automatic transmission

System overview, automatic transmission


The AF 22 (B204L/B234i/B258i) is an electronically controlled 4-speed automatic transmission which, in combination with different engine versions, is fitted in the Saab 900.

The transmission is controlled by an electronic system in which a transmission control module continually processes input signals and information received from a number of sensors. On the basis of the results obtained, it controls the automatic transmission's hydraulic system.

Compared with conventional hydraulically controlled transmissions, the AF22 has the following advantages:


Improved shifting performance and smoother shifting as torque is reduced when shifting takes place.

Improved fuel economy thanks to driving programmes optimized to fuel consumption.

Selection of varying driving programmes: NORMAL, SPORT, WINTER.

Reduced mechanical load on the entire transmission.

Self-diagnosis and storage of diagnostic trouble codes.