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MID 128 PID 103 FMI 9Severity: Warning

MID 128 PID 103 FMI 9: Turbocharger Speed Sensor - Signal Lost (Volvo)

Quick Answer

When MID 128 PID 103 FMI 9 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
MID 128 PID 103 FMI 9
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 MID 128 PID 103 FMI 9 soon and use the live-data and circuit checks below to determine how urgent the fault is.

Common Symptoms

  • Engine derate
  • Check engine lamp
  • Reduced power
  • Possible poor turbo response

Likely Causes

  • Turbo speed sensor failure
  • Open circuit in sensor wiring
  • Short to ground in signal circuit
  • Damaged sensor connector

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

  • Check sensor wiring for opens/shorts
  • Verify sensor connector integrity
  • Test sensor resistance (if applicable)
  • Inspect sensor mounting and air gap
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FitmentsMeaningHow it worksImagesDetailed guideOEM/Engine notesLocation hintScan tool checksStep-by-step diagnosticDecision guideMisdiagnosisDerate/inducementChecklistToolsPreventionCommunity discussionsCommunity videosCommunity notesShare

What does MID 128 PID 103 FMI 9 mean?

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When MID 128 PID 103 FMI 9 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 MID 128 PID 103 FMI 9 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 MID 128 PID 103 FMI 9

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MID 128 PID 103 FMI 9 - Turbo Speed Signal Lost

**Technical Detail**: This fault logs when the turbo speed sensor signal is completely lost [citation:3]. Without turbo speed input, the ECM cannot properly control the VGT or protect against overspeed.

📍 Sensor Location

The Turbo Speed Sensor is mounted in the center of the turbocharger and reads directly from the turbo shaft (not the vanes) [citation:8].

🔧 Why It Fails

**Common Failure Modes:**

1. **Sensor electrical failure** (internal open/short)

2. **Wiring damage** (heat from turbo, chafing)

3. **Connector issues** (corrosion, melted plastic)

4. **Tone wheel damage** (rare, but possible if turbo had debris)

🧪 Diagnosis

**Visual Inspection:**

  • Look for melted or brittle wiring near turbo
  • Check connector for heat damage
  • Inspect for oil leaks contaminating sensor

**Electrical Tests:**

  • Check for 5V supply (or battery voltage depending on sensor type)
  • Verify ground circuit
  • Test signal with oscilloscope if available (should show square wave)

🛠️ Parts & Images

The turbo speed sensor is often specific to the turbo model. Use OEM Volvo parts—aftermarket sensors for this application are notoriously problematic.

**Free images:**

  • "Turbo speed sensor" (generic automotive sensor)
  • "Turbocharger center housing" (shows sensor mounting location)

⚠️ Important Note

On some Volvo applications, this fault may also trigger if the ECM doesn't receive expected CAN messages from other modules (unlikely, but possible). Check for communication faults elsewhere.

Without turbo speed signal, the ECM enters a default boost control mode that may limit performance significantly.

Location hint for MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9 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 MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9

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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 MID 128 PID 103 FMI 9

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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.

What to check first for MID 128 PID 103 FMI 9

  1. Inspect connectors and harness near the affected component for corrosion, rubbing, or loose pins.
  2. Check for upstream causes (communications, sensors, air/fuel issues).
  3. Check for other active faults that may be upstream causes (communications, sensors, air/fuel issues).

If the fault repeats after clearing, diagnose it as ACTIVE and review companion codes and live data before replacing parts.

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No related faults found yet. Commonly seen with: SPN 5246, SPN 1569, SPN 4364, SPN 3719.

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