Radio Frequency Module (RF Hub) - Operation

OPERATION

The Radio Frequency Hub Module (RFHM) (also known as the RF 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 - The RFHM contains the controlling logic for the Brake Transmission Shift Interlock (BTSI) solenoid. The RFHM monitors inputs from the Ignition Node Module (IGNM) (also known as the Keyless Ignition Node/KIN) received over a private serial bus 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 the RFHM provides a communication interface through a private serial bus that supports either the Sentry Key Immobilizer System (SKIS) rotary key-operated IGnition Node Module (IGNM) (also known as the Keyless Ignition Node/KIN) functions, the Remote Keyless Entry (RKE) FOB with Integrated Key (FOBIK) rotary key-operated IGNM functions or the Passive Entry Keyless Go (PEKG) push button-operated IGNM functions. The RFHM also contains the controlling logic for the PEKG IGNM indicator and back lighting features.

- Passive Entry Keyless Go - In addition to monitoring inputs from the Keyless Go (KG) IGnition Node Module (IGNM) (also known as the Keyless Ignition Node/KIN), the RFHM is an RF and Low Frequency (LF) receiver for the optional Passive Entry Keyless Go (PEKG) FOB with Integrated Key (FOBIK). The RFHM contains the controlling logic for the PEKG systems and monitors inputs from the numerous Low Frequency (LF) antennas and the Smart door handles of the PE system.

- Remote Keyless Entry - The RFHM is an RF receiver that monitors RF inputs from the optional Remote Keyless Entry (RKE) transmitter 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 RKE system.

- Remote Start System - The RFHM is an RF receiver that monitors RF inputs received through the remote start antenna (long range) as well as through its own antenna (short range) from the Remote Keyless Entry (RKE) transmitter or the Passive Entry Keyless Go (PEKG) FOB with Integrated Key (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 remote start system. Note that on this vehicle the remote start antenna is directly connected to the RFHM.

- Sentry Key Immobilizer System - The RFHM monitors inputs from the IGnition Node Module (IGNM) (also known as the Keyless Ignition Node/KIN) received over a private serial bus and relays the appropriate electronic messages to other electronic modules in the vehicle over the CAN data bus to support the features of the Sentry Key Immobilizer System (SKIS). The RFHM also requires the unique SKIS PIN and secret key codes, which must be programmed into a replacement RFHM using a Replace RFHM Routine found in the diagnostic scan tool.

- Tire Pressure Monitor System - The RFHM is an RF receiver that monitors RF inputs received from the Tire Pressure Monitor (TPM) sensors 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 TPM system.

- Vehicle Theft Alarm System - The RFHM is an RF receiver that monitors RF inputs received from the Remote Keyless Entry (RKE) transmitter or the Passive Entry Keyless Go (PEKG) FOB with Integrated Key (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 RFHM 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 RFHM 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 RFHM to wake up and transmit on the CAN data bus.

The Body Control Module (BCM) stores and compares vehicle configuration data with the RFHM as well as with other Electronic Control Units (ECU) in the vehicle. This process is referred to as Programming Of Configuration of Systems Integrated (PROCSI) (also known as PROXI). 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.

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

The hard wired inputs and outputs of the RFHM 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 RFHM electronic controls or the communication between modules and other devices that provide some features of the RFHM-controlled systems. The most reliable, efficient and accurate means to diagnose the RFHM or the electronic controls and communication related to RFHM-controlled systems operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.