Module, Radio Frequency (RF Hub): Operation

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

The Radio Frequency Hub (RFH) module 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 (BTSI) Solenoid (Automatic Transmission) - The RFH contains the controlling logic for the BTSI solenoid. The RFH monitors the key position from the Ignition Node Module (IGNM) received over a private serial bus, hard wires 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, Ignition Node Module (IGNM) coil communicates with FOB with Integrated Key (FOBIK) through Low Frequency (LF) signals (125 KHz) then communicates it to RFH through a private Local Interface Network (LIN) bus, then the RFH sends CAN data bus to Body Control Module (BCM) for ignition status after valid key is verified. The RFH also contains the controlling logic for the Keyless Ignition Node (KIN) back lighting features.
Passive Entry - If Smart door handles or exterior deck lid release switch is activated, RFH sends and receives LF signals from five LF antennas which wake up and communicate with the FOBIK, and 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 (RKE) - The RFH is an RF receiver that monitors RF signals from RKE transmitter FOBIK and relays the appropriate electronic messages to the 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 from the RKE transmitter or the Passive Entry Keyless Go (PEKG) FOBIK. The RFH 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 (SKIS) - RFH uses a new high security encryption system called Advanced Encryption Standard (AES) for the SKIS. The new system marries FOBIKs, RFH, BCM and the Powertrain Control Module (PCM) with unique secret keys for each vehicle. Swapping parts ARE NOT ALLOWED in the new system as FOBIKs are not allowed to be programmed for more than one vehicle. Replacing any part of the system should be done only in authorized dealers using a diagnostic scan tool.
Tire Pressure Monitor (TPM) System - The RFH is an RF receiver that monitors RF signals received from the TPM sensors and then relays the appropriate electronic messages to other electronic modules in the vehicle over the CAN data bus to support the features of the TPM system.
Vehicle Theft Alarm (VTA) System - The RFH is an RF receiver that monitors RF signals received from the RKE transmitter or the PEKG FOBIK and then 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 bus.

The BCM stores and compares vehicle configuration data with the RFH as well as with other Electronic Control Units (ECU) in the vehicle. This process is referred to as the PROXI configuration. If a configuration mismatch is detected, the BCM sets a DTC. A configuration mismatch DTC will require the performance of a Restore BCM PROXI Configuration routine, or a PROXI Configuration Alignment routine using a diagnostic scan tool.

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 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 hard wired 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.