GF54.30-P-3018Q Displaying Fuel Quantity, Function

GF54.30-P-3018Q Displaying Fuel Quantity, Function

Component Identification:

Function
The fuel level and reserve gauge (A1p2) is a 39-segment LCD bar graph indicator. The fuel level and reserve gauge (A1p2) is switched on and off by the instrument cluster (A1).
The display readings are shown immediately after "circuit 15 ON"; the display run-up is dampened, but the run-down is not. A hysteresis is implemented to prevent segment jittering of readings near the segment limits.
The fuel level sensor, left half of tank (B4/1) and fuel level sensor, right half of tank (B4/2) change their resistance according to the level of fuel in the tank. The fuller the tank, the lower the resistance.

The resistance of the fuel level sensors is read in by the rear SAM control unit with fuse and relay module (N10/2). This converts the resistance values into a percentage. (A full tank is 100 %.) This percentage value is relayed by the rear SAM control unit with fuse and relay module (N10/2) on the interior CAN.
The instrument cluster (A1) registers this percentage from the interior CAN and uses this information as the basis for controlling the fuel level and reserve gauge (A1p2) and the fuel reserve indicator lamp (A1e4) as required.

Fuel level display
If "circuit 15 ON" is set at the electronic ignition switch control unit (N73), the present tank content is displayed in the fuel level and reserve gauge (A1p2). If the tank is refilled when "circuit 15 ON" is set at the electronic ignition switch control unit (N73) then the system detects that the tank has been refilled (display updated) only after a quantity of at least 9 liters has been added. The display is updated when "circuit 15 ON" is set again. There is always a delay before the display is updated.
This inhibits fluctuations in the display, e.g. due to cornering.

Reserve range
The reserve range extends from 0 to Reserve. This corresponds to a quantity of 0 to approx. 9 l. When the reserve level is reached, the fuel reserve indicator lamp (A1e4) lights up in yellow when the engine is running. (To prevent the lamp from flickering the control signal is transmitted with a delay.)

The system responds to malfunctions by moving the needle in the fuel level and reserve gauge (A1p2) to "0." The fuel reserve indicator lamp (A1e4) does not come on.