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SPN 110 FMI 4Severity: Warning

SPN 110 FMI 4: Engine coolant outlet temperature sensor circuit voltage low

Quick Answer

When SPN 110 FMI 4 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 4
Severity
Warning
Applies to
Check OEM application
Can I drive?
A short trip may be possible if the truck is operating normally and there is no stop-engine or critical warning. Diagnose SPN 110 FMI 4 soon and use the live-data and circuit checks below to determine how urgent the fault is.

Common Symptoms

  • MIL or check-engine light may illuminate
  • Engine coolant temperature reading may be implausibly low or unavailable

Likely Causes

  • Coolant temperature sensor circuit shorted to ground
  • Damaged or open sensor wiring
  • Engine coolant temperature sensor or connector failure

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

  • Inspect the coolant temperature sensor connector and harness
  • Test the sensor circuit for a short to ground or open circuit
  • Replace the sensor only after electrical testing confirms sensor failure
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What does SPN 110 FMI 4 mean?

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When SPN 110 FMI 4 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 4 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 4

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What SPN 110 FMI 4 means

SPN 110 identifies engine coolant outlet temperature.

FMI 4 indicates sensor voltage below normal or a circuit shorted toward a low source.

Detroit documentation describes SPN 110 FMI 4 as an engine coolant outlet temperature circuit failed-low condition.

What you may notice

The malfunction indicator lamp and check-engine light may illuminate.

The electronic coolant-temperature value may appear unrealistically low or may not represent actual engine temperature.

What to check first

Inspect the coolant-temperature sensor wiring for chafing, damaged insulation or a short to ground.

Check the connector for corrosion, bent terminals or poor contact.

Verify the sensor supply, ground and signal circuit using the OEM wiring diagram.

Important

This is primarily an electrical sensor-circuit fault. Do not replace thermostats, radiators or other cooling-system components until actual coolant temperature and sensor-circuit operation have been verified.

Location hint for SPN 110 FMI 4

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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 4

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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 4

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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 4

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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 4

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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 4 cause derate or inducement?

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A warning fault may allow continued operation, but the effect depends on the failed component and any companion faults.

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

“Do this first” checklist for SPN 110 FMI 4

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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 4

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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 4

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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 4

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