Module, Radio Frequency (RF Hub): Operation

WARNING: This page is about a different car, the 2020 Dodge Journey. However, it is still accessible from the selected car via links, so may be relevant.

The Radio Frequency Hub (RFH) is an integrated receiver (or base station) in the vehicle that communicates with other electronic modules in the vehicle over either the Controller Area Network (CAN) data bus or a private serial bus to support the following standard and optional vehicle features or systems.

Brake Transmission Shift Interlock System (for automatic Transmission only) - The RFH contains the controlling logic for the Brake Transmission Shift Interlock (BTSI) solenoid. The RFH monitors the key position from the Ignition Node Module (IGNM) received over a private serial bus, hardwired brake input as well as inputs received over the CAN data bus to perform the BTSI solenoid control functions.
Ignition Systems - Depending upon how the vehicle is equipped, Rotary Switch system or Keyless GO system. For rotary system, IGNM coil communicate with FOB with Integrated Key (FOBIK) through Low Frequency (LF) signals (125 KHz) then communicates it to RFH through a private serial bus, then RFH sends CAN data bus to BCM for ignition status after valid key is verified. The RFH also contains the controlling logic for the KG (KIN) back lighting features.
Passive Entry - If Smart door handles or exterior deck lid release switch is activated, RFH transmits and monitors LF signals from five Low Frequency (LF) antennas which wake up and communicate with the FOBIK, and Radio Frequency (RF) signals from FOBIK to verify the key, if valid key is recognized by RFH then RFH sends CAN data bus to BCM to lock or unlock the vehicle.
Remote Keyless Entry - The RFH is an RF receiver that monitors RF signals from Remote Keyless Entry (RKE) transmitter (FOBIK) and relays the appropriate electronic messages BCM module over the CAN data bus to support the features of RKE functions.
Remote Start System - The RFH is an RF receiver that monitors RF signals received through the remote start antenna (longer range) from the Remote Keyless Entry (RKE) transmitter or the Passive Entry Keyless Go (PEKG) FOBIK and relays the appropriate electronic messages to BCM over the CAN data bus to support all RKE functions including optional remote start function.
Sentry Key Immobilizer System - The SKIS uses low frequency radio frequency communication to obtain confirmation that the FOBIK is valid for operating the vehicle.
Vehicle Theft Alarm System - The RFH is an RF receiver that monitors RF signals received from the Remote Keyless Entry (RKE) transmitter or the Passive Entry Keyless Go (PEKG) FOBIK and relays the appropriate electronic messages to other electronic modules in the vehicle over the CAN data bus to support the features of the optional VTA system.

The RFH is connected to a fused B(+) circuit and has a path to a clean ground at all times. These connections allow it to remain functional regardless of the ignition switch status. Any input to the RFH that controls a vehicle system function that does not require that the ignition switch status be ON such as depressing a button on an RKE or FOBIK transmitter, prompts the RFH to wake up and transmit on the CAN data bus.

RFH uses On-Board Diagnostics (OBD) to monitor all of the Functions and circuits it controls, then sets active and stored Diagnostic Trouble Codes (DTC) for any monitored function faults it detects. RFH will also send electronic message requests to the Instrument Cluster (IC) (also known as the Instrument Panel Cluster/IPC) through the gate way module (BCM) for the display of certain textual warning messages related to some detected functions conditions or faults.

The hardwired inputs and outputs of the RFH may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the RFH electronic controls or the communication between modules and other devices that provide some features of the RFH controlled systems. The most reliable, efficient and accurate means to diagnose the RFH or the electronic controls and communication related to RFH controlled systems operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.