2004 Jeep Grand Cherokee Key Fob Programming: DIY Guide

Lost your key fob or need to program a new one for your 2004 Jeep Grand Cherokee? While dealerships often use specialized tools for this process, you might be surprised to learn that you can program your key fob yourself using readily available equipment. This guide will walk you through a DIY method to program your 2004 Jeep Grand Cherokee key fob, potentially saving you time and money.

The original procedure from Daimler Chrysler for Remote Keyless Entry (RKE) programming on Jeep Grand Cherokees (WJ models) from 1999 to 2002 suggested using dealer-specific Method C, requiring a DRB III scanning tool. However, this method isn’t the only route for 2004 models and earlier. It’s possible to bypass the need for expensive dealer tools and program your key fob using an ELM327 based OBD2 interface and a simple RS232 terminal software program. This method leverages the vehicle’s PCI bus through the OBD2 port to communicate directly with the Remote Keyless Entry system.

Your 2004 Jeep Grand Cherokee’s Remote Keyless Entry (RKE) system is integrated within the Passenger Door Module (PDM). This system has the capacity to store up to four different key fobs in its memory. By sending specific commands through the OBD2 port, we can put the RKE into programming mode and assign a memory slot for each key fob you wish to program. This process involves injecting commands into the vehicle’s PCI bus via the OBD2 port.

To successfully program your 2004 Jeep Grand Cherokee key fob, you will need the following:

• An ELM327 based OBD2 interface: This device acts as a bridge between your computer and your vehicle’s OBD2 port. These interfaces are widely available online.
• RS232 terminal software: This software allows your computer to communicate with the ELM327 interface. Popular options include PuTTY or Tera Term.
• Your new key fob: Ensure you have the correct type of key fob for your 2004 Jeep Grand Cherokee.

Once you have gathered these items, follow these step-by-step instructions to program your key fob:

Step 1: Setting up the ELM327 Interface

Before sending the programming commands, you need to configure your ELM327 interface using the RS232 terminal software. Connect the ELM327 interface to your vehicle’s OBD2 port (usually located under the dashboard on the driver’s side) and to your computer. Open your RS232 terminal software and configure it to connect to the COM port assigned to your ELM327 interface. Then, enter the following commands one by one, pressing Enter after each:

AT L1
AT H1
AT E1
AT SP2
AT RA A1
AT SH 24 A1 31

Let’s break down what each of these commands does:

• AT L1: Turns line feeds on, making the output easier to read.
• AT H1: Turns headers on, which is necessary for the communication protocol.
• AT E1: Turns echo on, so you can see the commands you are sending.
• AT SP2: Sets the communication protocol to VPW (Variable Pulse Width Modulation), which is used by the Jeep Grand Cherokee.
• AT RA A1: Sets the receive address to A1, allowing you to view responses from the Passenger Door Module (PDM).
• AT SH 24 A1 31: Sets the header bytes for the commands we will be sending. The ELM327 will automatically prepend these header bytes to subsequent commands.

Step 2: Putting the RKE into Programming Mode

With the ignition key in the “ON” position (engine off – KOEO), send the following command through the RS232 terminal to put the RKE into programming mode:

00 00 00

This command, combined with the header bytes set in the previous step, translates to the full command 24 A1 31 00 00 00 in HEX format. If successful, the vehicle should respond with:

26 A1 71 00 00 00

This response confirms that the RKE has entered programming mode.

Step 3: Specifying the Memory Slot

Next, you need to specify which memory slot you want to program for the new key fob. Send the following command, replacing “XX” with the desired memory slot number (01, 02, 03, or 04):

XX 00 00

For example, to program the key fob to memory slot 1, you would send:

01 00 00

This command, with the header, becomes 24 A1 31 XX 00 00. A successful response from the vehicle will be:

26 A1 71 XX 00 00

Step 4: Programming the Key Fob

Immediately after sending the memory slot command, take the key fob you want to program and press and hold either the “Lock” or “Unlock” button. Continue holding the button until you hear the door lock relays activate. This should happen within a few seconds. The activation of the door lock relays indicates that the key fob has been successfully programmed to the specified memory slot.

Step 5: Programming Additional Key Fobs (Optional)

If you have more key fobs to program, repeat Steps 2 through 4 for each additional fob. Remember to increment the memory slot number (XX) for each new key fob. For example, program the second key fob to memory slot 02, the third to slot 03, and so on. If you are unsure which slots are already used, starting from slot 02 or higher for new fobs is generally a safe approach, assuming your original key fob is in slot 1. You can also reprogram any slot, overwriting the previous key fob if needed. The slot numbers do not need to be programmed sequentially.

Step 6: завершение Programming

Once you have programmed all desired key fobs, turn the ignition key to the “OFF” position. This will terminate the programming mode.

Important Considerations and Disclaimer

While this DIY method has been successfully tested on a 2004 Jeep Grand Cherokee WJ and is likely to work for models from 1999 to 2004, it is crucial to proceed with caution and at your own risk. Interfacing with your vehicle’s OBD2 port involves sending commands directly to the vehicle’s systems, and incorrect commands could potentially lead to unintended consequences. However, based on testing, this specific procedure has not shown to cause harm to the vehicle or related modules. Always double-check your commands and connections. If you are uncomfortable with this procedure, it is always recommended to seek professional assistance from a qualified mechanic or dealership.

By following these steps carefully, you can program your 2004 Jeep Grand Cherokee key fob yourself, saving the cost and inconvenience of a dealership visit. This method offers a practical alternative for Jeep owners looking to manage their key fob programming at home.