Technical Description 59
Vehicle speed
µp
lJlJUlJU
39
The speedometer sends a speed signal to pin 39 of
the Trionic control module. This signal is a square
wave which varies between 0 V and battery positive
voltage (B+). At 19 mph (30 km/h) the frequency is
about 20 Hz.
This speed signal is used to:
• Ascertain which gear is engaged at the time
• Activate the SHIFT UP lamp
• Limit boost pressure in 1st gear (all turbo versions
except B234E)
• Activate speed limitation by limiting boost pressure
when maximum speed is attained (all turbo ver-
sions except B234E)
• Prevent adaptation of idle speed control when the
car is in motion.
If there is no speed signal the above functions
·
are
dropped
and boost pressure is limited to the lowest
gear-dependentpressure.
Saab9000
I
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