PRE-RELEASE
Speedometer with odometer and tripmeter.
| Speedometer with odometer and tripmeter. |
The main instrument unit is fitted with an electronic speedometer. The ESP control module receives the speed information from all wheel sensors. The information is processed and sent continuously on the P bus. The main instrument unit reads the information about the speed from the left rear wheel and converts this to km/h. If information from the left rear wheel is absent, information from the right rear wheel is used.
Information from the wheel sensors to the ESP control module is a square wave pulse which varies periodically between B+ and 0 V. This change occurs 29 times per wheel revolution.
With the wheels stationary, the voltage may be either B+ or 0 V.
The speedometer stepper motor is pulse-controlled and controlled internally from the main instrument unit control module which sends information on the speed to the bus.
| Odometer/tripmeter |
The main instrument unit's control module stores the distance driven and shows it on the information 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 odometer mileage can be read.
Information on the distance driven is sent out on the bus by the main instrument unit. This information is, for example, used by the SID control module.
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.
