This week, owners of the all-new Jeep® Grand Cherokee (WL) brought some important attention to the automaker that their vehicle’s key fobs continue to lose connection with the vehicle. As owners unlock their vehicles using the physical key located inside the key fob, their vehicles mistake the action as attempted theft and render the SUVs inoperable.
While it is unclear what is causing the issue, Stellantis has sent a notice to its dealer body for a “stop sale” of the vehicles due to faulty electronics. The document identifies the issue as a problem with the vehicle’s Radio Frequency Hub Module (RFHM), and “that it can intermittently result in a no-start condition”.
For those who don’t know what an RFHM does, it 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 Vehicles Only) – The RFHM contains the controlling logic for the Brake Transmission Shift Interlock (BTSI) solenoid. The RFHM 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 system. For rotary system, IGNM coil communicates with FOB with Integrated Key (FOBIK) through LF signals (125 kHz) then communicates it to RFHM through a private serial bus, then RFHM sends CAN data bus to for ignition status after the valid key is verified. The RFHM also contains the controlling logic for the KG (KIN) backlighting features.
- Passive Entry – If Smart door handles or exterior release switch is activated, RFHM fires 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 a valid key is recognized by RFHM then RFHM sends CAN data bus to Body Control Module (BCM) to lock or unlock the vehicle.
- Remote Keyless Entry – The RFHM is an RF receiver that monitors RF signals from the 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 RFHM is an RF receiver that monitors RF signals received through the remote start antenna (longer range) from the 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 – RFHM uses a new high-security encryption system called “Advanced Encryption Standard – AES” for Sentry Key Immobilizer System (SKIS). The new system marries FOBIKs, RFHM, BCM, ELV (if so equipped” and ECM with unique secret keys for each vehicle.
- Vehicle Theft Alarm System – The RFHM is an RF receiver that monitors RF signals received from the RKE transmitter or 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 Vehicle Theft Alarm (VTA) system.
Stellantis says said that it will not issue a recall for the 2022 Jeep Grand Cherokee and Grand Cherokee L, due to the issue. In a statement to MoparInsiders.com, a Stellantis spokesperson said, “This issue affects a limited number of vehicles and does not require a safety recall. We are contacting customers to advise them that free service is available.”
The notification sent to dealers states, “[Stellantis] will conduct a Customer Satisfaction Notification (CSN) to replace the RFHM. The remedy for this condition is not currently available. Dealers will be notified of the launch of this CSN by way of established communication methods. This CSN is estimated to launch in March of 2022.”
Stellantis has given the action an action identification number of Z23.
The Grand Cherokee is one of Stellantis North America’s most popular vehicles. The CSN does not affect the older 2022 Jeep Grand Cherokee (WK2), which continues to be on sale for the 2022 model year.
If you are a WL owner, be sure to join our dedicated Grand Cherokee (WL) owner’s forum (WLJeepForum.com) for the latest news, information, and rumors surrounding the fifth-generation Grand Cherokee.