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OBD II and Scan Tool Diagnostics Flashcards

7 cards from real ASE4 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What does MIL stand for in OBD II diagnostics?

    Answer: Malfunction Indicator Lamp

    MIL stands for Malfunction Indicator Lamp, the dashboard warning light that illuminates when the OBD II system confirms an emission-related fault.

  2. How many consecutive trips with the same fault detected does OBD II typically require before illuminating the MIL?

    Answer: Two trips

    Most OBD II systems require two consecutive trips with the same fault before illuminating the MIL, ensuring the fault is persistent and not a temporary glitch.

  3. What information is captured in OBD II freeze frame data?

    Answer: A snapshot of engine operating conditions at the moment a DTC was set

    Freeze frame data stores a snapshot of key engine parameters (RPM, load, coolant temp, fuel trim, etc.) at the instant a DTC was first detected, aiding diagnosis of intermittent faults.

  4. What is the standard OBD II communication protocol required in most vehicles manufactured since 2008?

    Answer: CAN (ISO 15765-4)

    CAN (Controller Area Network, ISO 15765-4) became the mandatory OBD II protocol for all US vehicles from 2008 onward, replacing older protocols like ISO 9141-2 and J1850.

  5. What does an 'incomplete' readiness monitor status on a scan tool indicate?

    Answer: The specific OBD II self-test for that system has not yet run and completed

    An incomplete readiness monitor means the OBD II system has not yet finished its self-diagnostic test for that specific emission component, typically because the drive cycle requirements haven't been met.

  6. A DTC with the prefix 'P0' indicates what type of fault code?

    Answer: Generic (SAE-standardized) powertrain fault

    The 'P0' prefix designates a generic SAE-defined powertrain DTC standardized across all OBD II compliant vehicles, regardless of manufacturer.

  7. What is the primary purpose of performing an OBD II drive cycle after a repair?

    Answer: To allow all readiness monitors to run and complete so emissions compliance can be verified

    A drive cycle is a specific series of driving conditions designed to satisfy the prerequisites for each OBD II readiness monitor, allowing them to run their self-tests and confirm the repair was successful.