GF54.21-P-4170RC Central Gateway Control Unit, Component Description
GF54.21-P-4170RC Central Gateway Control Unit, Component Description
- MODEL 171.4 as of model year 09 /YoM 08 model refinement package
N93 Central gateway control unit
Location
The central gateway control unit is located in the driver footwell under the instrument panel trim.
Tasks
The central gateway control unit has the following tasks:
- Central gateway
- Data container
- Global variant coding
- Standardization of signals
Central gateway
The central gateway control unit serves as an interface between the following databus systems:
- Diagnostic CAN
- Interior CAN
- Engine compartment CAN
Diagnostic CAN
The primary purpose of the diagnostic CAN is to allow connection of an external diagnostic unit. This is used to diagnose control units. This is achieved via diagnosis request messages which the diagnostic unit sends to the control unit in question.
The central gateway control unit responds to these diagnosis request messages with diagnosis response messages. The emergency call system control unit (N123/4) is also connected to the diagnostic CAN (with code (359) TELE AID emergency call system). The emergency call system control unit receives information from the interior CAN and engine compartment CAN.
Interior CAN
The central gateway control unit routes the information from the control units connected to the interior CAN to the control units connected to the engine compartment CAN by placing the information on the engine compartment CAN or establishes a connection between the diagnostic CAN and interior CAN for diagnostic purposes.
The control units connected to the engine compartment CAN only transmit and receive information with circuit 15 ON.
Engine compartment CAN
The central gateway control unit routes the information from the control units connected to the engine compartment CAN to the control units connected to the interior CAN by placing the information on the interior CAN or establishes a connection between the diagnostic CAN and engine compartment CAN for diagnostic purposes.
The control units connected to the engine compartment CAN only transmit and receive information with circuit 15 ON.
Data container
The data container in the central gateway control unit is a non- volatile mobile data memory.
Benefits: During production, vehicle-specific, test location-specific and control unit-specific data (e.g. production number, test status, partial tests not completed) are stored in the data container.
These data can be used in the subsequent tests for test sequence control. The total size of the data memory is 128 bytes.
Global variant coding
The central gateway control unit forwards globally-relevant information (e.g. model series, engine, equipment and national version) to the networked control units via interior CAN and engine compartment CAN. These data can be read out with a diagnostic unit and changed if necessary.
Standardization of signals
The central gateway control unit modifies the following signals to comply with uniform standards:
- Reverse gear signal
- Refrigerant pressure signal with code (580) Automatic air conditioning or with code (581) Comfort automatic air conditioning)
- Crash signal
Reverse gear signal
On vehicles with automatic transmission (with transmission 722) the ETC [EGS] control unit (N15/3) (with transmission 722.6) or the fully integrated transmission control unit (VGS) (Y3/8n4) (with transmission 722.9) transmits the reverse gear signal on the engine compartment CAN. The central gateway control unit read the signal in and replaces it with a standardized reverse gear signal which can be read in by the corresponding control units on the interior CAN. On vehicles with manual transmission (with transmission 716), the reverse gear signal is read in discretely by the driver-side SAM control unit with fuse and relay module (N10/1) and made available on the interior CAN. The central gateway control unit read the signal in and replaces it with a standardized reverse gear signal which can be read in by the corresponding control units on the interior CAN.
Refrigerant pressure signal
The signal from the refrigerant pressure sensor (B12) is read in by the driver-side SAM control unit and made available on the interior CAN. This signal is 16 bits long and has a value range of p = 0 to 35 bar at a resolution of 0.1 bar. The central gateway control unit processes this signal and places it on the engine compartment CAN with a modified signal length of 8 bits and a value range of p = 0 to 40 bar at a resolution of 0.5 bar.
Crash signal
The central gateway control unit reads in the crash signals from the driver-side SAM control unit and restraint systems control unit (N2/7), evaluates both signals and places the result on the engine compartment CAN.
