In the realm of second-generation on-board diagnostics, widely known as OBD2 diagnostics, interpreting fault codes read by automotive scanners across various communication protocols is essential. Among these, continuous codes and pending codes are frequently encountered. This article will guide you through identifying these codes based on their primary differences, considering the type of monitoring performed by the PCM.
Modern vehicles are equipped with numerous electronic control modules that manage diverse driving and performance conditions, alongside safety and comfort features. Specifically, the Powertrain Control Module (PCM) monitors vehicle conditions, particularly emissions, to alert the driver to any anomalies. Consequently, when an automotive technician uses a code reader or a conventional automotive scanner to check for stored faults, they may encounter both continuous and pending codes.
Continuous Fault Codes vs. Pending Fault Codes
One of the main distinguishing features is that continuous fault codes typically trigger the Malfunction Indicator Lamp (MIL), commonly known as the Check Engine Light, on the instrument panel. For a more precise understanding, let’s define each code type:
Continuous Codes (Permanent Codes)
These codes, also referred to as on-demand codes or permanent OBD2 codes, are directly linked to the MIL. If the MIL is illuminated, it’s generally because a continuous code has been generated. The PCM sets these codes based on tests of vehicle systems known as MONITORS. Continuous codes can arise from continuous monitoring or non-continuous monitoring that has been confirmed multiple times by the PCM. Reading these codes requires an automotive scan tool.
Alt text: OBD2 Connector Port in a Car, used for automotive diagnostics and reading permanent codes.
Pending Codes
Pending codes originate from non-continuous monitoring. While not necessarily less critical, their generation requires confirmation. Therefore, a series of strategies are employed to validate each code. Understanding these strategies is crucial because the confirmation process can take several driving cycles or specific road tests under particular conditions. Automotive technicians should clearly understand this concept to avoid confusion when encountering these codes stored in the PCM’s memory.
Alt text: Launch X431 V+ OBD2 Scanner Tool, used by mechanics to diagnose pending and permanent fault codes.
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