What is SPN 5055 & How to Solve It?

What is SPN 5055:

SPN 5055 refers to a proprietary fault related to the diesel exhaust aftertreatment system, often tied to DEF line heaters or dosing circuit issues. Without an FMI, this generally signals a general malfunction in DEF-related components.

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Why This Happens

• DEF line heater malfunction or short.
• Dosing valve fault affecting pressure or flow.
• Frozen DEF lines or poor heating performance.
• Inconsistent current draw in heating circuits.
• ECM unable to confirm heater activation.

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How to Fix It

1. Inspect DEF lines for damage, blockage, or freezing.
2. Test heater circuits for resistance and continuity.
3. Replace faulty heater elements or damaged connectors.
4. Run DEF system diagnostics for dosing performance.
5. Clear the code and monitor heater and flow response.

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How to Avoid It Before It Happens

1. Always test DEF heater function before cold weather.
2. Flush and clean DEF lines periodically.
3. Use sealed DEF storage to avoid contamination.
4. Replace heating components before failure during winter months.

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