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SPN 110 FMI 2

SPN 110 FMI 2: Engine coolant temperature signal erratic or implausible

Quick Answer

When SPN 110 FMI 2 sets, the ECM is indicating a fault condition involving the component or system named in the code.

OEM definitions and thresholds can vary, so confirm the exact meaning with service information or a capable diagnostic tool.

Code
SPN 110 FMI 2
Severity
Info
Applies to
Check OEM application
Can I drive?
The immediate driving effect of SPN 110 FMI 2 depends on whether the fault is active, the component involved, and any companion codes. If it repeats after clearing, diagnose it as an active fault rather than continuing to reset it.

Common Symptoms

  • Coolant temperature reading may fluctuate or disagree with engine conditions
  • Check-engine warning may appear intermittently

Likely Causes

  • Coolant temperature sensor drift or intermittent failure
  • Loose, corroded or damaged sensor wiring
  • Temperature reading outside the expected rational range

Quick Diagnostic Checks

Check first
  1. 1Scan for companion codes and record freeze-frame data (if available).
  2. 2Inspect connectors, harness rub points, and pins for corrosion.
  3. 3Check for other active faults that may be upstream causes (communications, sensors, air/fuel issues).
  4. 4After repair, clear codes and confirm the fault stays inactive after a drive cycle.

Common Fixes

  • Compare coolant temperature with other temperature data and actual engine conditions
  • Inspect the coolant temperature sensor connector and wiring
  • Replace the sensor only if circuit and rationality testing supports sensor failure
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FitmentsMeaningHow it worksImagesDetailed guideOEM/Engine notesLocation hintScan tool checksStep-by-step diagnosticDecision guideMisdiagnosisDerate/inducementChecklistToolsPreventionCommunity discussionsCommunity videosCommunity notesShare

What does SPN 110 FMI 2 mean?

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When SPN 110 FMI 2 sets, the ECM is indicating a fault condition involving the component or system named in the code.

OEM definitions and thresholds can vary, so confirm the exact meaning with service information or a capable diagnostic tool.

Treat repeat faults as ACTIVE and diagnose using live data, wiring checks, and basic inspections before replacing parts.

How this system works (why SPN 110 FMI 2 happens)

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Most modern fault logic is based on expected versus actual sensor readings, timing windows, circuit checks, and plausibility tests.

A stored code can come from a temporary event, while a repeatable active code gives you a much better diagnostic target.

The goal is to identify whether the failure is electrical, mechanical, sensor-related, or caused by another upstream fault before replacing components.

Detailed guide for SPN 110 FMI 2

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What SPN 110 FMI 2 means

SPN 110 identifies engine coolant temperature. FMI 2 indicates data that is erratic, intermittent or incorrect.

Detroit troubleshooting information describes this condition as coolant temperature outside the expected rational range or a temperature signal that has drifted high or low.

What to check first

Compare the coolant-temperature reading with engine oil temperature, ambient conditions and actual engine warm-up behavior.

Inspect the coolant-temperature sensor connector for corrosion, loose terminals or contamination. Check the harness for intermittent opens, shorts or damage.

Monitor live coolant-temperature data while the engine warms. An implausible jump, drop or value that does not track actual engine temperature can indicate a sensor or circuit problem.

Before replacing parts

Do not replace cooling-system components solely because of an FMI 2 fault. First determine whether the engine is actually overheating or whether the temperature signal itself is inaccurate.

Use OEM specifications because acceptable temperature differences and rationality limits vary between engine families.

Location hint for SPN 110 FMI 2

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Component location varies by OEM and chassis. Use your engine’s service manual to confirm the sensor/valve location before replacing parts.

Tip: Inspect connectors and harness routing before replacing parts.

Scan tool checks for SPN 110 FMI 2

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  • Check status: ACTIVE vs INACTIVE / stored and review freeze-frame data when available.
  • Record companion codes and diagnose the earliest or most upstream fault first.
  • Compare live sensor values with expected operating conditions and inspect wiring and connectors.
  • Clear and re-test under similar conditions only after completing the initial inspection.

If your tool can’t run actuator tests, you can still diagnose a lot with careful inspection + repeatability testing.

Step-by-step diagnostic for SPN 110 FMI 2

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  1. Visual inspection (fast wins). Harness routing, connector pins, hoses/lines (if applicable), and obvious damage.
  2. Check fluid sanity. Not applicable unless your fault is fluid-related. Focus on inspections + repeatability.
  3. Confirm the fault is ACTIVE. Stored-only faults can be old events.
  4. Review live data and circuit values. Use OEM diagnostic software (examples: Cummins INSITE, Detroit DDDL, PACCAR DAVIE4) or a capable heavy-duty scan tool to review the affected signal, commanded/actual values when applicable, and related sensor data.
  5. Verify after repair. Clear codes, road test, confirm it stays inactive.

Decision guide (fast path) for SPN 110 FMI 2

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  • If the fault is STORED only → inspect, clear, and monitor. If it returns, treat it as active.
  • If ACTIVE → inspect the named component, connector, harness, supply/ground, and live-data plausibility.
  • If multiple codes are present → diagnose the earliest or most upstream code first.

Common misdiagnosis mistakes for SPN 110 FMI 2

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  • Replacing sensors or components without checking wiring, grounds, connector fitment, and companion codes.
  • Clearing the fault repeatedly without confirming whether it is ACTIVE and repeatable.
  • Missing an upstream fault that is causing the displayed code as a secondary symptom.

Will SPN 110 FMI 2 cause derate or inducement?

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This fault may not require immediate shutdown, but repeated or active faults should still be diagnosed.

Exact behavior depends on ECM calibration and which companion faults are active.

“Do this first” checklist for SPN 110 FMI 2

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  • Scan for companion codes and record freeze-frame data (if available).
  • Inspect connectors, harness rub points, and pins for corrosion.
  • Check for other active faults that may be upstream causes (communications, sensors, air/fuel issues).
  • After repair, clear codes and confirm the fault stays inactive after a drive cycle.

Tools needed to diagnose SPN 110 FMI 2

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  • Basic hand tools + good lighting for inspection
  • Multimeter for connector/power/ground checks (if wiring suspected)
  • OEM diagnostic software (examples: Cummins INSITE, Detroit DDDL, PACCAR DAVIE4) (or equivalent scan tool) for live data and supported diagnostic tests

Prevention tips to avoid repeat SPN 110 FMI 2

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  • Fix small wiring/connector issues early before they become repeat faults.
  • During service, inspect harness routing and clamp points near heat/vibration.
  • Don’t ignore intermittent faults. “Erratic” usually gets worse.
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Mechanic community notes for SPN 110 FMI 2

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