Description And Operation
The Radio Frequency Hub (RFH) carries out a number of functions which depend on the type of key that comes with the vehicle. It may have two different types of key:
If the vehicle has the first type of key, it will not have the second type and vice versa.
FOBIK: RFH functions
- When the vehicle has a FOBIK, the RFH carries out the following functions:
- Passive Entry
- Key recognition (RFH is part of the Immobilizer system)
- Tire Pressure Monitor (TPM) (tire pressure detection) function
Since it has to recognize the keys, their codes are programmed in the RFH. The ignition switch also comprises a Start/Stop button named Keyless Ignition Node (KIN). The button is connected electrically to the RFH through a Local Interface Network (LIN) data bus and a connection with an analogue signal called "Redundant Run". This signal permits the RFH to determine whether the Start/Stop button has been pressed if there is a fault on the LIN data bus.
To carry out the Passive Entry function, the RFH needs 4 low-frequency peripheral aerials that allow the module to identify and locate the keys.
| Aerial Name | Aerial position. |
|---|---|
| 1 | Rear left door |
| 2 | Rear right door |
| 3 | Luggage compartment |
| 4 | Dashboard |
The RFH is located in the rear overhead compartment of the vehicle. The module cannot be adjusted or repaired and, if damaged or ineffective, it must be replaced.
The Passive Entry system also makes use of the two door locking buttons on the front handles, through which vehicle users can request door locking. Inside the handles are capacitive sensors (one per handle) which allow the RFH to determine whether the user's hand is near the inside of the handle.
The RFH detects the vicinity of the key to the vehicle through aerials. The key recognition and authentication stage begins when the vehicle user brings their hand towards the inside of the handle. At that moment, the RFH reads the key ID and the secret code stored in it. If the RFH identifies it as the key encoded in its memory, it sends the request to unlock the doors or the driver door only (depending on the setting in the "my vehicle" menu) to the Body Control Module (BCM).
Mechanical groove key: RFH functions
- If the vehicle comes with a key with mechanical groove, the RFH carries out only the following function:
- TPM (tire pressure detection) function
In this case the RFH is not a component of the immobilizer function, since the ID codes of the vehicle's keys are stored in the BCM. Consequently, the ignition switch no longer comprises the KIN (Start/Stop button) but the classic mechanical switch.