Description And Operation: Description

The RFH module 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:

• Fobik key
  Fig 1: Fobik Key

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• Mechanical groove key.

If the vehicle has the first type of key, it can't have the second type and vice versa.

Fig 2: Fobik Key Functions

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Fobik key: RFH functions 

- When the car has a Fobik key, the RFH module carries out the following functions:

• Passive Entry
• Key recognition (RFH is part of the Immobilizer system)
• TPMS (tyre pressure detection) function.

Fig 3: RFH Module & Run/Start Button Circuit Diagram

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Since it has to recognize the keys, their codes are programmed in the RFH module. The ignition switch also comprises a Start/Stop button named KIN module. The button is connected electrically to the RFH module through a LIN line 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 line.

Fig 4: Antenna Locations

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To carry out the Passive Entry function, the RFH module needs 5 low-frequency peripheral aerials that allow the module to identify and locate the keys.

Fig 5: RFH Module & Antenna Circuit Diagram

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The RFHM is located in the rear overhead compartment of the vehicle. The module be adjusted or repaired and, if damaged or ineffective, it must be replaced.

Fig 6: RFH Module & Door Locks Circuit Diagram

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The Passive Entry system also makes use of the two door locking buttons on the front handles, through which car users can request door locking. Inside the handles are capacitive sensors (one per handle) which allow the RFH module to determine whether the user's hand is near the inside of the handle.

The RFH module 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 module 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 car" menu) to the BCM.

Fig 7: Mechanical Groove Key

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Mechanical groove key: RFH functions 

- If the vehicle comes with key with mechanical groove, the RFH module carries out only the following function:

• TPMS (tire pressure detection) function

In this case the RFH module 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 module (Start/Stop button) but the classic mechanical switch.