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The electronic speedometer is used to display vehicle speed. The speedometer is driven by a stepper motor.
Measuring the vehicle speed
The instrument cluster receives from the ESP control unit (N47-5) the wheel speeds required for the
computation of vehicle speed via the Controller Area Network (data bus/CAN bus) (CAN). The tire size is
taken into account when calculating the speed. Coding takes place using STAR DIAGNOSIS.
Assessment of wheel speed signals:
The wheel speed signals are compared against each other and thus checked in terms of plausibility. If
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there are no significant deviations, the vehicle speed is calculated from the rotational speed of the left
front wheel.
If the individual wheel speed signals vary substantially, the speed signals may be faulty or the vehicle
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may be cornering. If, by comparing the wheel speeds on both sides of the vehicle, the instrument
cluster determines that the car is cornering, the vehicle speed is calculated from the mean value of the
front wheel speeds.
If the comparisons indicate one or more faulty wheel speed signals, the vehicle speed is then
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calculated on the basis of highest wheel speed. This also applies if an error message is received
instead of a wheel speed signal.
The travel distance is determined as for the vehicle speed.
Instrument cluster, component description
ESP control unit, component description
DISPLAY OPERATING CONDITIONS, FUNCTION - GF54.30-P-3041MCU
MODEL 451.3/4
Shown on code (K07) Speedometer (miles)
Fig. 65: Identifying Indicator Displays
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Gear indicator in manual mode
The gear indicator displays the current gear engaged.
GF54.30-P-6000MCU
A1
GF42.45-P-5118MCU
N47-5
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