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Speedometer with odometer and trip meter, Trionic T7

Speedometer with odometer and trip meter, Trionic T7

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 is in the form of a square pulse which varies periodically between B+ and 0 V. The main instrument unit supplies the output with current and the ABS control module grounds 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 by the main instrument unit's control module which converts the frequency modulated signal into km/h or mph. A correction, depending on the programmed tyre size, is performed and the speed information is sent out on 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 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 zeroized 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 distance driven is sent out on the bus by the main instrument unit. This information is used by the SID and other units.

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.