Cummins SPN 105 FMI 4: Intake Manifold Temperature Diagnosis
SPN 105 FMI 4 (FMI 4) — Engine Intake Manifold 1 Temperature — Voltage Below Normal or Shorted to Low Source
Quick Answer
On Cummins, SPN 105 FMI 4 is a Intake Manifold Temperature fault (Voltage Below Normal or Shorted to Low Source). Prove wiring/live data first; do not parts-cannon the component.
Overview: Cummins SPN 105 FMI 4
On Cummins, SPN 105 FMI 4 is a Intake Manifold Temperature fault (Voltage Below Normal or Shorted to Low Source). Prove wiring/live data first; do not parts-cannon the component. This guide covers symptoms, root causes, live-data checks, and misdiagnoses for Cummins platforms.
Repair Snapshot
Time
1 - 3 Hours
Difficulty
Intermediate
Parts Cost
$50 - $800
Dealer Labor
$350+
Tools Required
- Cummins INSITE
- Noregon JPRO
- Multimeter
What SPN 105 FMI 4 Means
SPN 105 FMI 4 on Cummins means Engine Intake Manifold 1 Temperature — Voltage Below Normal or Shorted to Low Source. Confirm Check IAT vs ambient; inspect connector resistance with Cummins INSITE / Noregon JPRO before replacing the intake manifold temperature.
Symptoms Drivers Notice
- Check-engine / amber warning lamp illuminated.
- Soft power, unstable idle, or poor response when intake manifold temperature data is irrational.
- Live data for intake manifold temperature fails rationality vs mechanical gauge or partner sensors.
- Codes may return immediately after clearing if root cause remains.
Most Likely Root Causes
Common Misdiagnoses (Don't Waste Parts)
Why it happens:
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Why it happens:
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Why it happens:
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Master Tech Commentary
Mechanic's Notes
Shop tip (Cummins): For SPN 105 FMI 4, prove Check IAT vs ambient; inspect connector resistance before quoting the Intake Manifold Temperature. Common false path is replacing the sensor when the harness or reference circuit is the failure.
Step-by-Step Diagnostic Procedure
- Step 1: Connect Cummins INSITE or Noregon JPRO and record SPN 105 FMI 4 with freeze-frame load/temp.
- Step 2: Inspect harness and connector at the intake manifold temperature for chafe, corrosion, and bent pins.
- Step 3: Verify 5V reference / ground / signal integrity with a multimeter where applicable.
- Step 4: Check IAT vs ambient; inspect connector resistance
- Step 5: Repair the proven fault, clear only after repair, and verify under the same conditions as freeze-frame.
Live Data & Freeze-Frame Tips
Log Intake Manifold Temperature with Cummins INSITE under freeze-frame conditions. Check IAT vs ambient; inspect connector resistance. Compare to a mechanical gauge when pressure/temperature related.
When to Limp In vs Tow
Drive carefully to a shop if lamps are warning-only and power remains controllable; tow if power loss is severe.
Related Fault Codes
Frequently Asked Questions
What does Cummins SPN 105 FMI 4 mean?
It indicates a Intake Manifold Temperature fault: Voltage Below Normal or Shorted to Low Source. Confirm with live data and wiring tests before parts replacement.
Can SPN 105 cause a derate?
It can contribute to limp behavior if the ECM loses trust in critical data, especially when paired with other faults.
What tools diagnose this best?
Cummins INSITE and Noregon JPRO, plus a quality multimeter and mechanical gauges for pressure/temperature checks.
Should I clear the code first?
No. Capture freeze-frame and the full stack first. Clear only after the repair and verification.
More Cummins codes on this system
- Cummins SPN 102 FMI 3 — Boost Pressure Sensor Circuit
- Cummins SPN 105 FMI 0 — Intake Manifold Temperature Sensor
- Cummins Guide VGT-Cal — Variable Geometry Turbo Actuator
- Cummins SPN 3364 FMI 9 — DEF Dosing Unit
- Cummins SPN 157 FMI 16 — Engine Fuel Rail Pressure
- Cummins SPN 520372 FMI 16 — DEF Dosing System
- Cummins SPN 5246 FMI 15 — SCR Inducement
- Cummins SPN 2659 FMI 18 — DEF Dosing Unit
Guides that go deeper
- SPN 1569 FMI 31: Engine Protection Shutdown and Safe Recovery Steps [2026 Diagnostic Guide]
SPN 1569 FMI 31 means engine protection shutdown is active—not the root fault. Read stacked codes, verify oil and coolant, then reset only after the trigger is fixed.
- SPN 3031 DEF Tank Temperature Fault: Heater, Sensor, or Wiring
SPN 3031 points at DEF tank temperature strategy faults. Confirm heaters, sensor rationality, and harness chafe before replacing the tank assembly.
- Detroit DDDL Basics: Finding the Root Code Behind a Derate
Use Detroit DDDL the right way: separate root SPN/FMI faults from inducement result codes, read derate stage data, and stop replacing parts on guesses.