Speedometer, odometer and trip meter (TC/ABS)
| Speedometer, odometer and trip meter (TC/ABS) |
The main instrument unit has an electronic speedometer. The TC/ABS control module receives vehicle speed data from all wheel sensors. The information is processed and transmitted continuously on the P bus. The main instrument unit reads the speed information from the rear left wheel and converts this to km/h.
The information to the TC/ABS from the wheel sensors is in the form of a square wave that varies between B+ and 0 v 29 times per wheel revolution.
With the wheels stationary, the voltage may be either B+ or 0 V.
The speedometer is supplied with current and is controlled by the main instrument unit control module, which also sends information on the speed to the bus.
| 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, 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.
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