Engine
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    truck

    Why Is My Check Engine Light Flashing?

    Typical repair cost: $50–$3,500

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    Common Symptoms

    Rapidly blinking CEL
    Engine shaking
    Loss of power
    Smell of raw fuel from exhaust
    Loud exhaust pops

    Most Likely Causes

    1

    Active misfire

    Flashing CEL specifically means cylinder misfire severe enough to damage the catalytic converter — codes P0300-P0312.

    2

    Failed coil pack

    #1 cause of sudden flashing CEL — single coil dies and dumps fuel into the cat.

    3

    Failed injector

    Stuck-open or dead injector floods or starves a cylinder.

    4

    Compression loss / valve issue

    Burnt valve or broken spring shows as persistent single-cylinder misfire.

    How a Shop Diagnoses It

    1. 1.Stop driving. Scan immediately for misfire codes.
    2. 2.Swap suspect coil/plug to another cylinder; recheck which cylinder misfires.
    3. 3.Compression and leak-down test on the offending cylinder.

    When to see a professional

    A flashing CEL means damage is happening NOW — every minute of driving costs you catalytic converter life ($800-$3,000).

    Find a shop near you

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    Related Engine problems

    Check engine light
    $0–$1200 typical repair
    Diesel losing power
    $200–$8000 typical repair
    Oil leak
    $100–$1800 typical repair
    Flashing CEL
    $80–$2000 typical repair
    Engine knocking
    $50–$8000 typical repair

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