Key programming with a DRB3 scan tool can be essential for certain Jeep models, especially older ones like the XJ Cherokee. However, encountering a “no communication” error can be frustrating. This article explores potential causes and troubleshooting steps for DRB3 communication failures, specifically focusing on key programming for a 1999 Jeep Cherokee (XJ).
Understanding the DRB3 and OBDII Communication
The DRB3 scan tool is a dealer-level diagnostic tool used for Chrysler vehicles. It relies on specific communication protocols to interact with the vehicle’s various modules. One common issue is the inability of the DRB3 to establish communication, preventing tasks like key fob programming. Often, generic OBDII code readers can still communicate and clear codes even when the DRB3 fails. This discrepancy leads to confusion about the communication pathways.
Contrary to some beliefs, both the DRB3 and aftermarket OBDII readers utilize the same physical connection – the Data Link Connector (DLC), commonly known as the OBDII port. While there are separate circuits within the DLC for different communication protocols (CCD Data Bus and SCI), the physical connector remains the same.
The 1999 Jeep XJ utilizes the Chrysler Collision Detection (CCD) Data Bus for general communication between modules and the Serial Communication Interface (SCI) for specific tasks, including keyless entry programming. The DRB3 needs to correctly interface with both.
Potential Causes of DRB3 Communication Failure
A common misconception is that separate wires within the DLC cater specifically to the DRB3 and generic OBDII readers. In reality, the issue often stems from problems within the vehicle’s communication systems themselves. A “no communication” error with the DRB3 can result from several factors:
- Faulty SCI Circuits: Open or shorted circuits in the SCI Transmit or Receive lines can prevent the DRB3 from communicating with necessary modules like the Powertrain Control Module (PCM), Transmission Control Module (TCM), and Anti-lock Brake System Control Module (ABS). Since the PCM handles SCI Receive commands (e.g., clearing codes, programming), a problem here is particularly problematic for key programming.
- Incorrect DRB3 Setup: The DRB3 requires proper configuration, including accurate vehicle identification number (VIN) input, before connecting to the DLC. Failure to do so can prevent communication.
- Grounding Issues: A poor ground connection can disrupt communication between the DRB3 and the vehicle’s modules.
- Damaged DLC: A damaged or corroded DLC can physically prevent proper connection and communication.
- Module Failure: While less likely, a faulty PCM, TCM, or keyless entry module can cause communication breakdowns.
Fig 1: A typical OBD-II connector
Troubleshooting Steps
- Verify OBDII Functionality: Confirm that a generic OBDII code reader can successfully connect and communicate with the vehicle. This helps rule out fundamental DLC or CCD Bus issues.
- Check DRB3 Setup: Ensure the DRB3 is correctly configured with the correct VIN and vehicle information. Consult the DRB3 user manual for specific instructions.
Fig 2: DRB-III scan tool
- Inspect the DLC: Visually examine the DLC for any damage, corrosion, or loose pins. Clean the connector with electrical contact cleaner if necessary.
- Check Ground Connections: Inspect ground connections related to the PCM and relevant modules. Ensure they are clean, tight, and free of corrosion. Refer to the factory service manual for specific ground locations.
- Test SCI Circuits: Using a multimeter, test for continuity and shorts in the SCI Transmit and Receive circuits between the DLC and the respective modules. Consult the wiring diagram in the factory service manual for specific pin locations and wire colors.
Conclusion
Troubleshooting DRB3 communication issues requires a systematic approach focusing on potential causes related to both the scan tool and the vehicle’s communication systems. By understanding the communication protocols involved and following these troubleshooting steps, you can increase your chances of successfully diagnosing and resolving the problem, enabling tasks like key programming using the DRB3 scan tool. If the problem persists after these checks, further diagnostics by a qualified automotive technician might be necessary.
