Module, Radio Frequency (RF Hub): Operation

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 ignition switch position from the Keyless Ignition Node (KIN) 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  - The KIN communicates with the FOBIK through LF signals (125 KHz), then communicates it to the RFH through a private serial bus. The RFH then sends CAN data to the BCM for ignition status after a valid key is verified. The RFH also contains the controlling logic for the Keyless Go backlighting features.
• Passive Entry  - If Smart door handles or the exterior deck lid release switch is activated, the RFH sends and monitors LF signals from five Low Frequency (LF) antennas which wake up and communicate with the FOB with Integrated Key (FOBIK), and RF signals from FOBIK to verify the key. If a valid key is recognized by the RFH, then the RFH sends CAN data bus to the BCM to lock or unlock the vehicle.
• Remote Keyless Entry  - The RFH is an RF receiver that monitors RF signals from Passive Entry Keyless Go (PEKG) 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 (longer range) from the 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 (SKIS)  - The SKIS uses low frequency radio frequency communication to obtain confirmation that the FOBIK is valid for operating the vehicle.
• Tire Pressure Monitor System  - The RFH is an RF receiver that monitors RF signals received from the Tire Pressure Monitor (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. When the vehicle is equipped with remote start and Passive Entry (PE) the tire pressure signal is also received by the remote start antenna.
• Vehicle Theft Alarm System  - The RFH is an RF receiver that monitors RF signals received from the 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 a 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 Panel Cluster (IPC) through the Body Control Module (BCM) gateway 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.