Programming Your 2003 Jeep Grand Cherokee Key Fob: A Step-by-Step Guide

Lost your key fob or need to program a new one for your 2003 Jeep Grand Cherokee? While dealerships often require specialized tools and can charge hefty fees for this service, you might be surprised to learn that you can program a key fob yourself using readily available equipment and a straightforward procedure. This guide provides a detailed, step-by-step method to program your 2003 Jeep Grand Cherokee Key Fob, potentially saving you time and money.

Understanding Key Fob Programming on Your WJ Grand Cherokee

The 2003 Jeep Grand Cherokee (WJ model) utilizes a Remote Keyless Entry (RKE) system integrated into the Passenger Door Module (PDM). This system can store up to four different key fobs in its memory. Traditionally, dealer programming methods (like Method C described in older technical service bulletins) were thought to be necessary for WJ models. However, it’s been discovered that a more accessible method exists, leveraging the vehicle’s OBD2 port.

This DIY method involves sending specific commands via the OBD2 port to put the RKE system into programming mode and assign a memory slot to your new key fob. This bypasses the need for expensive dealer-specific scanning tools and allows you to program your key fob using an ELM327 based OBD2 interface and a simple RS232 terminal software program on your computer.

Tools You Will Need

Before you begin, ensure you have the following:

• A new key fob: Purchase a compatible key fob for your 2003 Jeep Grand Cherokee. Ensure it’s the correct frequency and type for your vehicle.
• ELM327 OBD2 interface: This is a common and affordable interface that allows your computer to communicate with your vehicle’s OBD2 port. You can find these online from various retailers.
• RS232 terminal software: This software allows you to send commands to the ELM327 interface. Popular options include PuTTY, Tera Term, or similar terminal programs.
• A computer with an RS232 port or a USB to RS232 adapter: Your computer will need to connect to the ELM327 interface. If your computer doesn’t have a native RS232 port, a USB to RS232 adapter can be used.

Step-by-Step Key Fob Programming Procedure

Important Notes Before You Begin:

• Ensure your Jeep Grand Cherokee is a WJ model (1999-2004). While tested on a 2004 model, this method is likely applicable to the 2003 and other WJ models within this range.
• This procedure requires the ignition to be in the “Key On, Engine Off” (KOEO) position.
• Proceed with caution and at your own risk when interfacing with your vehicle’s OBD2 port. While this method has been successfully tested without harm, always be mindful and follow the instructions carefully.

Programming Steps:

1. Connect the ELM327 interface: Plug your ELM327 OBD2 interface into the OBD2 port of your 2003 Jeep Grand Cherokee. This port is typically located under the dashboard on the driver’s side.

2. Establish communication with the ELM327: Open your RS232 terminal software and configure it to connect to the COM port associated with your ELM327 interface. Refer to your ELM327 documentation for specific COM port settings and baud rates.

3. Initialize the ELM327 interface: Once connected, you need to send a series of AT commands to configure the ELM327. Type the following commands one by one into your terminal software, pressing “Enter” after each command:

   • AT L1 (Turns line feeds on)
   • AT H1 (Turns headers on)
   • AT E1 (Turns echo on)
   • AT SP2 (Sets communication protocol to VPW – Variable Pulse Width Modulation, used by Chrysler vehicles)
   • AT RA A1 (Sets receive address to A1 for viewing responses from the PDM – Passenger Door Module)
   • AT SH 24 A1 31 (Sets the header bytes for the commands we will send)

   You should receive “OK” responses after each successful command.

4. Enter RKE Programming Mode: To put the RKE system into programming mode, send the following command (without the header bytes, as the ELM327 will automatically prepend them):

   • 00 00 00

   Type this into your terminal and press “Enter”. A successful response from the vehicle will be:

   • 26 A1 71 00 00 00

   You should see this response in your terminal window if the command was successful.

5. Specify Memory Slot: Now you need to specify which memory slot to program for your new key fob. Memory slots are numbered 01, 02, 03, and 04. If you are programming your first key fob, or want to overwrite the first slot, use 01. For subsequent key fobs, you can use 02, 03, or 04. Send the following command, replacing “XX” with your desired memory slot number in hexadecimal format (01, 02, 03, or 04):

   • XX 00 00 (For example, for slot 1, send 01 00 00)

   Press “Enter”. A successful response will be:

   • 26 A1 71 XX 00 00 (Where XX corresponds to the slot you specified).

6. Activate Key Fob Programming: Immediately after sending the memory slot command, take your new key fob and press and hold either the “Lock” or “Unlock” button. Keep holding the button until you hear the door lock relays activate. This usually happens within a few seconds. The sound of the door locks clicking indicates that the key fob has been successfully programmed to the selected memory slot.

7. Repeat for Additional Key Fobs (If Needed): If you need to program more key fobs, repeat steps 4 through 6, incrementing the memory slot number (XX) for each additional key fob.

8. Exit Programming Mode: Once you have programmed all desired key fobs, turn the ignition key to the “Off” position. This will terminate the programming mode.

9. Test Your Key Fobs: Test each programmed key fob to ensure it correctly locks and unlocks the doors of your 2003 Jeep Grand Cherokee.

Important Considerations and Disclaimer

• Existing Key Fobs: If you have an existing working key fob, it is likely programmed to memory slot 1. You can program new key fobs to slots 2, 3, and 4 without affecting the original key fob. Alternatively, you can reprogram the existing key fob to slot 1 again or overwrite any slot.
• Non-Sequential Slots: Memory slots do not need to be programmed sequentially. You can program slot 3, then slot 1, then slot 4, for example.
• Risk and Responsibility: While this procedure has been reported to be safe and effective, modifying your vehicle’s electronic systems always carries some risk. Proceed at your own risk, and ensure you understand each step before proceeding. [keyfobprog.com] is not responsible for any damage or issues that may arise from following this guide.

By following these steps carefully, you can successfully program a new key fob for your 2003 Jeep Grand Cherokee, regaining the convenience of remote keyless entry without the need for expensive dealership services.