9-5 Aero (9600) L4-2.3L Turbo (B235) HO (2000)
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Speedometer Head: Description and Operation
Speedometer With Odometer and Trip Meter
Speedometer
The main instrument unit is fitted with an electronic speedometer. The ABS control module receives information on vehicle speed from the rear left-hand
wheel speed sensor. This information is processed and conveyed continuously to terminal 10 (K12) of the main instrument unit's control module.
The information in the form of a square wave pulse varies periodically between B+ and 0 V. This takes place 29 times per wheel revolution.
With the wheels stationary, the voltage may be either B+ or 0 V.
The main instrument unit uses the frequency to calculate the vehicle speed.
The speedometer is supplied with current and controlled from the main instrument unit's control module, which also sends information on the vehicle
speed to the buses.
Odometer/trip meter
The main instrument unit's control module stores the distance driven and shows it on the odometer display. The display has a six-digit register which the
control module updates continuously from 000000 to 999999 km (or miles). The trip meter has a four-digit register which starts at 000.0 and runs to
999.9 km (or miles). When the ignition is ON, the trip meter can be zeroed with the reset button. If the reset button is pressed while the ignition is OFF,
the display lights up for 20 seconds and the mileage can be read.
Information on the distance driven is sent out on the bus by the main instrument unit. This information is used by the SID unit, for example.
Diagnostics
If the vehicle speed information exceeds 270 km/h, diagnostic trouble code B1705 is set.
The function has its own diagnostics in the sending system.
