For automotive technicians and car enthusiasts alike, OBD2 scan tools are indispensable for diagnosing and addressing vehicle issues. Making sense of fault codes is only the first step; understanding how your vehicle’s system manages these faults is crucial for effective repairs. This is where the concepts of fault shedding, fault healing, and fault erasing become vital when using your 0302 Scan Tool or any OBD II diagnostic device.
Let’s delve into how Porsche’s OBD II system, as outlined in their manual, handles fault management, providing insights applicable to many modern vehicles and enhancing your proficiency with your 0302 scan tool.
Fault Shedding Explained
When your 0302 scan tool detects a fault during a diagnostic routine, the system initially registers it as a “suspected fault.” Simultaneously, a “fault shedding counter” begins. This counter is designed to prevent false positives. If the same fault is detected again in subsequent diagnostic cycles within a specific timeframe, the shedding counter decreases. Once this counter reaches zero, the fault is considered “shedded.” This mechanism ensures that only persistent issues are flagged as active problems, improving the accuracy of diagnostics performed with your 0302 scan tool.
The Process of Fault Healing
Conversely, the system also accounts for faults that may resolve themselves. When a fault is initially detected by your 0302 scan tool, a “fault healing counter” is activated. If, in subsequent diagnostic routines, the fault is no longer detected in the same area, this healing counter decreases. If the counter reaches zero, the fault is deemed “healed.” Importantly, if the fault had previously triggered the Malfunction Indicator Light (MIL), or check engine light, it will be switched off, provided no other active faults are present. This intelligent system, accessible through your 0302 scan tool, helps distinguish between transient and resolved issues.
Decoding the Fault Erasing Counter
Each fault detected by your 0302 scan tool is associated with an “individual fault erasing counter.” This counter dictates how long a fault remains stored in the system’s memory. Upon initial detection, the erasing counter is set to 80.
If a fault, initially unshedded, is later recognized as healed, the counter resets to 10. If a shedded fault is detected again, the counter is set to 40 and remains at this value until fault healing is recognized. After each warm-up operating cycle, the fault erasing counter decrements by 1, assuming the fault is currently recognized as either unshedded or healed. Crucially, when this counter reaches zero, the fault is permanently erased from the system’s memory. This detailed fault erasing mechanism, while operating in the background, is important to understand when interpreting historical fault data with your 0302 scan tool.
Understanding these fault management processes—shedding, healing, and erasing—provides a deeper insight into how your vehicle’s OBD II system operates and enhances your ability to effectively utilize your 0302 scan tool for accurate diagnostics and efficient vehicle maintenance.
