Speedometer with odometer/tripmeter
| Speedometer with odometer/tripmeter |
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, with the main instrument unit supplying the current to the output and the ABS control module grounding it. 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 converts the frequency modulated signal to km/h or mph. The value is corrected for the tyre size and then the information is sent to the buses.
| Odometer/tripmeter |
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 tripmeter has a four-digit register which starts at 000.0 and runs to 999.9 km (or miles). When the ignition is ON, the tripmeter 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, for example.
Diagnosis
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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