The OBD2 port on your 2015 Ford Fusion is a critical component for diagnosing and troubleshooting vehicle issues. However, some electrical problems can manifest as malfunctions seemingly related to the OBD2 port, specifically pin 6. This article delves into troubleshooting a complex electrical issue on a 2015 Ford Fusion SE 2.0L Turbo, focusing on the HS1 CAN bus system and its connection to the OBD2 port. This information is intended to guide those experiencing similar issues and comfortable with advanced automotive electrical diagnostics. Disclaimer: Working with automotive electrical systems can be dangerous. If you’re not comfortable with these procedures, consult a qualified mechanic.
Understanding the Problem: Intermittent System Shutdowns
The primary issue was intermittent shutdowns of various systems, including the AC, radio, center console, windows, and door locks. These failures were often accompanied by system restart chimes upon recovery. Testing revealed that grounding pin 6 of the OBD2 port (part of the HS1 CAN bus system) consistently replicated the complete system shutdown.
Identifying the Culprit: The HS1 CAN Bus System
The Ford Fusion utilizes four CAN bus networks: HS1, HS2, HS3, and MS CAN. Each network consists of a twisted pair of wires (+ and -) to minimize electrical interference. Through rigorous testing with a bi-directional scan tool, Ford Forscan, and an oscilloscope, it was determined that only grounding the HS1 network could trigger a complete system failure mimicking the original problem. Other networks affected only subsets of the systems.
Tracing the HS1 Network
The HS1 CAN bus connects critical modules:
- PCM (Powertrain Control Module): The main car computer.
- BCM (Body Control Module): Controls various body functions.
- APIM (Accessory Protocol Interface Module): Manages infotainment and other accessories.
- DLC (Data Link Connector): The OBD2 port.
- Splice 17 and Splice 124: Junction points within the wiring harness.
A ground fault anywhere within this network, including the modules, wiring, or splices, could be the root cause.
Troubleshooting Steps and Findings
The troubleshooting process involved:
- Visual inspection: Checking for damaged wiring, loose connections, and corroded splices.
- Resistance testing: Measuring resistance across the HS1 network to identify potential shorts to ground.
- Signal analysis: Using an oscilloscope to monitor CAN bus signals for anomalies.
- Module testing: Using Ford Forscan to check for communication errors and module functionality.
During this process, a faulty puddle lamp in the driver’s side mirror was discovered and replaced, though its connection to the primary issue remains unclear. A potential workaround involving a key fob sequence (unlock twice, lock twice, hold lock for 10 seconds) to reset the system was also noted but not verified. The heated seat and rear window defrost functionalities, damaged during previous repairs, were confirmed operational through the scan tool, suggesting a control signal issue rather than a component failure.
Conclusion and Next Steps
While the root cause of the intermittent shutdowns remains elusive, the problem has been isolated to the HS1 CAN bus network. Future steps involve a more detailed inspection of the wiring harness, particularly around splice points 17 and 124, and potentially replacing suspect modules. The key takeaway is the importance of systematically isolating the problem using diagnostic tools and a thorough understanding of the vehicle’s electrical architecture. This case highlights that simply removing the OBD2 port will not resolve underlying CAN bus communication issues.
