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MID 128 PID 100 FMI 5Severity: Warning

MID 128 PID 100 FMI 5: Engine Oil Pressure Sensor - Open Circuit (Volvo)

Quick Answer

When MID 128 PID 100 FMI 5 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 100 FMI 5
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 100 FMI 5 soon and use the live-data and circuit checks below to determine how urgent the fault is.

Common Symptoms

  • Oil pressure gauge reads 0
  • Yellow warning lamp
  • No oil pressure reading in diagnostic data
  • May affect engine protection strategies

Likely Causes

  • Open circuit in 5V supply wire
  • Open circuit in signal wire
  • Short to ground in signal wire
  • Short to ground in 5V supply

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 continuity of 5V supply from ECM to sensor
  • Check continuity of signal wire
  • Check for shorts to ground
  • Verify sensor resistance (if applicable)
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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 100 FMI 5 mean?

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When MID 128 PID 100 FMI 5 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 100 FMI 5 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 100 FMI 5

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MID 128 PID 100 FMI 5 - Oil Pressure Sensor Open/Low Current

**Technical Detail**: This fault triggers when signal voltage drops below 0.08V, indicating either an open circuit or a short to ground [citation:1][citation:2].

🔍 The "Open Circuit" Reality

FMI 5 is the electrical version of a "disconnected" fault. The ECM sees no signal current because:

  • The wire is broken somewhere
  • The sensor is unplugged
  • The wire is shorted directly to ground

🧪 Diagnosis by the Numbers

**Using a multimeter:**

1. Key OFF, disconnect sensor

2. Check resistance between sensor signal pin and ground:

  • Should be high (open circuit) with sensor disconnected

3. Check continuity of 5V supply from ECM to sensor

4. Check continuity of ground circuit from ECM to sensor

**On Volvo D13:**

The oil pressure sensor harness often rubs against the engine block near the turbocharger [citation:4]. After 500k miles, the insulation wears through and wires can break or short.

📸 Image Search Terms

  • "Broken wire harness abrasion" (generic automotive)
  • "Engine harness chafing repair" (shows typical damage)

👨‍🔧 Real Mechanic Wisdom

*"When I see FMI 5 on an oil pressure sensor, I start by looking for physical damage. Had a truck where a rat chewed through three wires—took 10 minutes to find, 30 minutes to repair, saved customer $1000 in unnecessary parts."* — Mobile truck repair

⚡ Quick Verification

If you jumper signal to ground at the sensor connector (with key ON), the voltage should drop to near 0V and the fault should change (or you'll see 0 pressure in data). This confirms wiring to ECM is intact.

Location hint for MID 128 PID 100 FMI 5

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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 100 FMI 5

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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 100 FMI 5

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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 100 FMI 5

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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 100 FMI 5

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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 100 FMI 5 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 100 FMI 5

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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 100 FMI 5

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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 100 FMI 5

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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 100 FMI 5

  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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