What Does P0688 Code Mean?

    OBD-II Code P0688 is defined as a ECM/PCM Power Relay Sense Circuit/Open

    The engine computer (PCM) power relay controls battery voltage to the PCM. If the PCM detects an incorrect voltage signal from the power relay, it will set code P0688.

    P0688 Symptoms

    • Engine may not start
    • Hard or no start in cold weather

    Common Problems That Trigger the P0688 Code

    • Powertrain Control Module (PCM) failure
    • Powertrain Control Module (PCM) power relay failure
    • Wiring issue

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