Comfort Displays, Function - GF54.30-P-3043RD

Model 172.4 

Function requirements, general 

• Instrument cluster (A1) activated Comfort displays in general

The comfort displays provide a fast overview of the information, which is not required to operate the vehicle.

The comfort display function includes the following subfunctions:

• Function sequence for displaying outside temperature
• Function sequence for displaying the time
• Function sequence for scale illumination of instrument cluster

Function sequence for displaying outside temperature

The outside temperature is detected by the outside temperature sensor (B14). The front SAM control unit with fuse and relay module (N10/1) reads in the signal from the outside temperature sensor directly, uses this signal to calculate the outside temperature and sends the outside temperature via the interior CAN (CAN B) to the instrument cluster.

The outside temperature is displayed in °C or °F in the instrument cluster's multifunction display (A1 p13) corresponding to the country coding.

The following parameters must also be taken into account to determine a correct value of outside temperature:

• Vehicle speed (falsification of value through air stream)
• Coolant temperature (falsification of value through radiant heat) The vehicle speed is calculated on the basis of the wheel speeds. The Electronic Stability Program control unit (N30/4) transmits information about the wheel speeds to the instrument cluster via chassis CAN 1 (CAN E1), the front SAM control unit and chassis CAN 2 (CAN E2) as of 01.03.2016 and via the chassis CAN (CAN E) up to 29.02.2016.

The CDI control unit (N3/9) (with diesel engine) or the ME-SFI control unit (N3/10) (with gasoline engine) transmits information about the coolant temperature to the instrument cluster via chassis CAN 1, the front SAM control unit and chassis CAN 2 as of 01.03.2016 and via the chassis CAN up to 29.02.2016.

The coolant temperature has an influence on the outside temperature indicator as follows:

• Coolant temperature T < 60°C:

The current outside temperature value is always shown.

• Coolant temperature T > 60°C and "Engine running" or "Drive train operational" signal is set:

At vehicle speeds of v < 20 km/h (with vehicle deceleration), the outside temperature display is only changed if the measured outside temperature value drops. At vehicle speeds of v = 20 and 45 km/h, rising outside temperatures are displayed after a delay period of t = 3 min.

At vehicle speeds of v > 45 km/h rising outside temperatures are displayed after a delay period of t = 90 s.

The CDI control unit or the ME-SFI control unit sends the "engine running" or "drivetrain operational" signal to the instrument cluster via chassis CAN 1, the front SAM control unit and chassis CAN 2 as of 01.03.2016 and via the chassis CAN up to 29.02.2016.

If the vehicle speed signal is faulty, rising outside temperatures are updated every t = 10 min in an attenuated manner.

• Coolant temperature T > 60°C and "Engine running" or "Drive train operational" signal is not set:

A delay period of maximum t = 1 h prevents an apparent increase in outside temperature from being displayed that is caused by heat dissipated from the engine. A rise in display value is not permitted during this delay period. With circuit 15 OFF, the last measured outside temperature value is stored and then displayed when the circuit is reactivated.

If, in the meantime, the measured outside temperature has dropped below the stored value, the currently measured temperature is displayed after t = 8 seconds.

The electronic ignition lock control unit (N73) sends the status of circuit 15 to the instrument cluster via the interior CAN as of 01.03.2016 and via the chassis CAN up to 29.02.2016.

The display range for the outside temperature is between T = -40 and

+85°C or between T = -40 and +185°F.

If the instrument cluster receives implausible values or no values at all for coolant temperature, the display of outside temperature is controlled as if the coolant temperature were T > 60°C.

Function sequence for displaying the time

The time is shown in the multifunction display and for vehicles with code 246 (Analog clock), also on the analog clock (A70/1).

The time can either be entered manually in the system settings or it is updated automatically through the received GPS data (with code 522

(Audio 20 radio) or code 531 (COMMAND APS)). The radio (A2) (with code 505 (Radio 20 NTG5, non-navigation-capable) or code 522 (Audio 20 radio)) or the COMMAND controller unit (A40/3) (with code 531 (COMMAND APS)) transmits information about the time by a dedicated protocol via the interior CAN to the instrument cluster (time synchronization). The instrument cluster adopts the time and, in vehicles with code 246 (Analog clock), sends it via the interior CAN to the front SAM control unit. The front SAM control unit actuates the analog clock over the instrument panel LIN (LIN 1) accordingly.

Detailed information on changing system settings is available in a separate document.

Function sequence for scale illumination of instrument cluster

Switching on the standing light (circuit 58) (except model 172.475) or the circuit 15R activates the scale illumination on the instrument cluster.

For model 172.475 the scale illumination for the instrument cluster is always activated as from circuit 15R ON.

The instrument cluster receives this information and switches on the scale illumination.

The brightness is automatically adjusted to suit the lighting conditions in the vehicle interior by a phototransistor integrated in the instrument cluster. The brightness can also be personalized by actuating the brightness control instrument illumination (A1r1).

The front SAM control unit sends the status of the standing lights actuation (circuit 58) over the interior CAN to the instrument cluster. The electronic ignition lock control unit sends the status of circuit 15 via the interior CAN as of 01.03.2016, and via the chassis CAN up to 29.02.2016, to the instrument cluster.

If the instrument cluster was activated by the driver door being opened, it only switches on the default screen of the multifunction display. This switches off again after t = 30 s. If an active warning is displayed, this run-on time extends to t = 120 s.

If the ambient illumination function is activated using the instrument cluster, this is automatically switched on when the vehicle is unlocked by radio or infrared. This causes the "standing lights actuation active" status (circuit 58 ON) to be set, thereby also activating the scale illumination of the instrument cluster. If the driver door is then opened, the ambient illumination goes off. The "Standing lights actuation active" status (circuit 58 ON) is canceled and the instrument cluster deactivates the scale illumination.

	Electrical function schematic of instrument cluster, comfort display	Model 172.4 as of model year 2017	PE54.30-P-2056-97TAB
		Model 172.4 up to model year 2017	PE54.30-P-2056-97TAA
	Overview of system components, instrument cluster (IC) component description		GF54.30-P-9996RD