Peterbilt SPN 105 FMI 3: Intake Manifold Temperature Diagnosis
SPN 105 FMI 3 (FMI 3) — Engine Intake Manifold 1 Temperature — Voltage Above Normal or Shorted to High Source
Quick Answer
On Peterbilt, SPN 105 FMI 3 is a Intake Manifold Temperature fault (Voltage Above Normal or Shorted to High Source). Prove wiring/live data first; do not parts-cannon the component.
Overview: Peterbilt SPN 105 FMI 3
On Peterbilt, SPN 105 FMI 3 is a Intake Manifold Temperature fault (Voltage Above Normal or Shorted to High Source). Prove wiring/live data first; do not parts-cannon the component. This guide covers symptoms, root causes, live-data checks, and misdiagnoses for Peterbilt platforms.
Repair Snapshot
Time
1 - 3 Hours
Difficulty
Intermediate
Parts Cost
$50 - $800
Dealer Labor
$350+
Tools Required
- PACCAR Davie
- Noregon JPRO
- Multimeter
What SPN 105 FMI 3 Means
SPN 105 FMI 3 on Peterbilt means Engine Intake Manifold 1 Temperature — Voltage Above Normal or Shorted to High Source. Confirm Check IAT vs ambient; inspect connector resistance with PACCAR Davie / 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 (Peterbilt): For SPN 105 FMI 3, 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 PACCAR Davie or Noregon JPRO and record SPN 105 FMI 3 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 PACCAR Davie 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 Peterbilt SPN 105 FMI 3 mean?
It indicates a Intake Manifold Temperature fault: Voltage Above Normal or Shorted to High 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?
PACCAR Davie 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 Peterbilt codes on this system
- Peterbilt SPN 412 FMI 5 — Turbocharger Boost Control
- Peterbilt SPN 102 FMI 16 — Boost Pressure Sensor / Overboost Condition
- Peterbilt SPN 1127 FMI 16 — Turbocharger 1 Boost Pressure
- Peterbilt SPN 3364 FMI 9 — DEF Quality Sensor
- Peterbilt SPN 168 FMI 0 — Battery / ECU Power Supply Voltage
- Peterbilt SPN 100 FMI 1 — Engine Oil Pressure Sensor / Oil Pressure Circuit
- Peterbilt SPN 111 FMI 1 — Engine Coolant Level Sensor
- Peterbilt SPN 132 FMI 2 — Engine Inlet Air Mass Flow Rate Sensor
Guides that go deeper
- 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.
- 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.
- 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.