Speedometer with odometer and trip meter
| Speedometer with odometer and trip meter |
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 0V. The main instrument supplies the current and the ABS control module grounds the output. 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 powered and controlled by the main instrument unit control module, which converts the frequency modulated signal to km/h or mph. A correction is made depending on the programmed tyre size, whereby the speed information is put on the bus.
| Odometer/trip meter |
The main instrument unit control module stores the distance driven and shows it on the odometer display. The display contains a six-digit counter which the control module continuously updates from 000000 to 999999 km (or miles). The trip meter has a four-digit counter which starts at 000.0 and runs to 999.9 km (or miles). With the ignition ON, the trip meter is zeroed with the reset button. The display will be activated for 20 seconds if the reset button is pressed with the ignition OFF. An odometer reading is then obtained.
Information on the driven distance is put on the bus by the main instrument unit. The information is used by SID, among others.
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.
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