GF54.30-P-3025SX Display Speed, Function

GF54.30-P-3025SX Display Speed, Function

Component Identification:

General
The electronic speedometer is used to display vehicle speed. The electronic speedometer is displayed in the multifunction display. The electronic speedometer can be displayed as follows:
^ Ring speedometer
^ Strip speedometer (on vehicles with code (610) Night View Assist)
In addition to the electronic speedometer an additional speedo can be faded in in the multifunction display.

Measuring the vehicle speed
The wheel speeds from the following sensors are evaluated to calculate the vehicle speed:
^ Left front rpm sensor (L6/1/)
^ Right front rpm sensor (L6/2/)
^ Left rear rpm sensor (L6/3/)
^ Right rear rpm sensor (L6/4/)

Additional speedometer shown on model 221 up to 31.8.06

Function
The additional speedometer indicates the speed of the vehicle in a digital numerical display in the lower left multifunction display. The dimensional unit of speedometer scale of the electronic speedometer is as follows in relation to the dimensional unit of the additional speedometer:
^ If the dimensional unit of the speedometer scale of the electronic speedometer is kilometers, the additional speedo is displayed in miles.
^ If the dimensional unit of the speedometer scale of the electronic speedometer is miles, the additional speedo is displayed in kilometers.

Component Identification:

Switching on or off additional speedometer
The additional speedometer is switched on or off as follows:
^ use the system selection button (S110s3) of the left multifunction steering wheel button group (S110) to select the "Settings" menu item.
^ Using the scroll forward/back button (S110s1) of the Left multifunction steering wheel button group select the "additional speedometer" menu item and confirm with the OK button (S110s6).
^ Use the OK button to switch the additional speedo on or off.
^ The displayed function is stored and exited using the "Back" and SBS off button (S110s4).

Evaluating the wheel speed signals
Since the wheels do not always rotate at the same speed, all 4 wheel speeds must be evaluated. As the evaluation procedure is very complex, a simplified version is described here:
^ The individual wheel speeds are compared and submitted to a plausibility check. If there are no significant differences, the vehicle speed is determined using the rotational speed of the left front wheel.
^ If the individual wheel speed signals differ considerably, the speed signals may be faulty or the vehicle may be cornering.
^ If appropriate comparison of the wheel speeds (between the two sides of the vehicle) by the instrument cluster indicates that the vehicle is cornering, the speed is determined from the mean value of the front wheel speeds.
^ If the comparisons indicate one or more incorrect wheel speeds, the speed is calculated from the highest wheel speed. This also applies if an error message is received instead of a rotational wheel speed. In this case a corresponding fault message is also output.
If error messages are received for all wheel speeds, the speed 0 km/h or 0 mph is displayed (speed display pointer at start of scale).

Component Identification:

Information flow and networking
Reading in the data for the vehicle speed signal:
^ The left front rpm sensor, right front rpm sensor, left rear rpm sensor and right rear rpm sensor are read in by the ESP control unit.
^ The ESP control unit places the rpm sensor signals on the chassis CAN.
^ The central gateway control unit reads in the signals from the chassis CAN and places them on the central CAN.
^ The instrument cluster reads in the signals from the central CAN and calculates the vehicle speed from them. The instrument cluster indicates the vehicle speed as a ring or strip speedometer (only on code (610) Night View Assist) in the electronic speedometer and places the vehicle speed signal on the central CAN.

Cruise control display
For the cruise control function the speedometer scale in the multifunction display is displayed in the form of a segment band in the ring speedometer or band speedometer of the electronic speedometer. The individual segments symbolize various vehicle speed ranges and can be actuated individually with different brightness and color.
The brightened segments are shown as follows:
^ The cruise control without limiter is displayed with a brightened segment above the speed to be regulated by the cruise control.
^ The cruise control with limiter (except code (494) USA version) is displayed with a brightened segment between the cruise control speed and limiter speed.
^ The cruise control with Distronic (with code (219) Distronic (DTR)) or cruise control with Distronic Plus (with code (233) Distronic Plus) is displayed by a brightened segment between the measured speed of the vehicle driving in front and the adjusted speed.

Limiter, except code (494) USA version
With the functionality of the limiter a maximum speed below the maximum speed of the vehicle actually achievable or (if switched on) up to the adjusted speed of the "Permanent Limiters". If the vehicle gets close to the adjusted speed, the limiter ensures that the adjusted maximum vehicle speed is maintained by engine intervention. The limiter is adjustable in the range from 30 km/h up to the maximum speed. The adjustment takes place via the CC [TPM] switch (S40/4) in steps of ten and one (km/h or mph). In the electronic speedometer in the multifunction display the segments of the ring speedometer or the strip speedometer then light up from the scale start up to the adjusted value.

Permanent Limiter, except code (494) USA version
A permanent speed limit (adjustable in 10-km/h steps of 160 km/h to 240 km/h or in 10-mph steps from 100 mph to 150 mph) can be adjusted via the "Settings" menu and the "Speedtronik" submenu item in the multifunction display. The adjustment takes place via the buttons of the left multifunction steering wheel button group and the "Back" and VCS [SBS] off button. The permanent speed limit is displayed by a segment band above the electronic speedometer from the start of the scale up to the adjusted speed limit value. Correspondingly a warning message appears in the multifunction display and a warning chime is output when the adjusted vehicle speed is exceeded.