Case IH Error Code ENG 418 — What It Means and How to Fix It

Applies to: All Tier 4 Case IH equipment, Magnum, Puma, Steiger/Quadtrac, Axial-Flow Combines

WARNING — DEF/SCR system fault. Likely water contamination.

Drain the fuel/water separator immediately. Check DEF fluid quality — if cloudy or discoloured, drain and replace with fresh ISO 22241 certified DEF.

CIH ENG 418Case IHManually verified

DEF/SCR System Fault — Water in Fuel / SCR Efficiency

ENG 418 indicates water in the fuel filter that needs draining. ENG 3146 indicates SCR system efficiency faults. These codes frequently co-occur due to water contamination in fuel or DEF fluid. These are the codes that make farmers curse Tier 4 emissions equipment.

Repair difficulty

DIY — Basic tools

Repair time

15 min

Dealer cost

$200-8000

What to check first

  1. 1

    Open the drain valve on the fuel/water separator and drain until clean fuel flows — takes 2 minutes

  2. 2

    Check DEF fluid: should be clear and colourless. If cloudy, contaminated, or crystallised around the cap, drain and replace.

  3. 3

    Check the DEF filler cap seal — a damaged seal allows moisture in. Replace if the seal is perished.

Likely causes

  1. 1

    Water in fuel— Most likely

    DIY

    Drain the water separator. Common in humid climates or with poor fuel storage.

  2. 2

    Water or contamination in DEF tank— Most likely

    DIY

    Drain the DEF tank, flush, and refill with fresh, quality DEF from a sealed container.

  3. 3

    DEF tank cap seal damaged— Possible

    DIY

    A damaged seal allows moisture and contaminants in.

  4. 4

    DEF quality degraded (old stock, heat exposure)— Possible

    DIY

    DEF degrades above 30°C. Don't use open or sun-exposed containers.

  5. 5

    NOx sensor failure— Possible

    Shop

    Particularly for ENG 3146 codes. Requires dealer diagnosis.

  6. 6

    SCR catalyst degradation— Less common

    Shop

    Typically only on equipment with 5,000+ hours.

Parts needed

Tools needed

  • Drain container
  • Filter wrench
  • Clean funnel (for DEF — do not contaminate)
  • Clean rags

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Pro tip

Buy DEF from a reputable supplier in sealed containers. Never leave DEF containers open or in the sun. Keep fuel tanks full when parking to minimise condensation. Many recurring DEF codes are caused by bad fluid, not bad equipment.

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