Our automotive experts have put together the following information about the P0684 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P0684 code.

OBD II Fault Code

  • OBD II P0684

    OBD-II Code Hard or no start in cold weather is defined as a Glow Plug Control Module to PCM Communication Circuit

    The Glow Plug Module controls the glow plugs used on diesel engines to preheat the cylinder before the engine is started. If the engine control module (PCM) cannot communicate with the Glow Plug Module, the PCM will set code P0684.

    Hard or no start in cold weather Symptoms

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

    Common Problems That Trigger the P0684 Code

    • Glow plug control module failure
    • Powertrain Control Module (PCM) failure
    • Wiring issue
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