SPN 1188 FMI 9Engine Protection
Engine Turbocharger 1 Compressor Intake Temperature - Abnormal Update Rate
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Connector Pinout — in guided session
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Overview
Fault Code
SPN 1188 / FMI 9
Category
Engine Protection
Derate Risk
No
Regen Inhibit
No
Inducement Risk
No
Component Location: Turbocharger compressor intake temperature sensor is located on the intake piping at the compressor inlet of the turbocharger, typically on the cold-side air duct near the turbo housing.
Common Symptoms
- Active fault code SPN 1188 FMI 9 logged in ECM
- Intermittent or missing turbocharger compressor intake temperature data
- Engine derate or power reduction due to engine protection mode
- DPF regen inhibited or delayed
- Possible increased fueling or poor combustion efficiency
- Loss of communication with sensor over data link
Root Causes
- Faulty or failed turbocharger compressor intake temperature sensor Damaged, corroded, or loose wiring harness connector at sensor Open or short circuit in sensor signal or supply wiring CAN or J1939 data link communication fault causing abnormal update rate ECM software or calibration issue causing data drop-out Failed or damaged sensor module communicating over data link Chafed wiring causing intermittent signal loss
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Derate Behavior
Power Derate
No
System Interactions
SPN 1188 FMI 9 interacts with the following systems and may trigger cascading faults if not resolved promptly.
ECM communication — J1939 network faults can affect all connected modules
Engine protection — ECM may trigger derate to prevent damage
Aftertreatment — engine protection derates can affect regen strategy
Common Diagnostic Mistakes
Replacing the sensor without verifying wiring continuity and supply voltage first.
Clearing codes without identifying and resolving the root cause — the fault will return.
Ignoring related active faults — cascading faults often share a root cause.
Skipping the connector inspection — corrosion and damaged pins are a leading cause of sensor faults.
Condemning the ECM before exhausting all wiring and component tests.
Related Faults in This Category
OEM System Resources
ASE Training Resources
Diagnostic Engine v7.0
Related Diagnostic Articles
Deep-dive diagnostic page: SPN 1188 FMI 9 — Full FSM Sequence & Repair Steps — includes wiring notes, sensor specs, and gated repair procedures.
Authority References
Diagnostic procedures on this page are informed by OEM service literature and industry standards.
Cummins QuickServe OnlineOfficial Cummins service manuals, fault code lookup, and TSB database.Detroit Diesel DiagnoCentralDetroit Diesel diagnostic procedures, DDDL documentation, and service literature.PACCAR MX Engine ServicePACCAR MX-11 and MX-13 engine service documentation and DAVIE diagnostic guides.Volvo/Mack Tech ToolVolvo and Mack engine fault code reference and PTT/Tech Tool diagnostic procedures.ASE — Diesel Truck Technician CertificationNational Institute for Automotive Service Excellence — T2 Diesel Engines certification standards.EPA Aftertreatment & Emissions GuidelinesU.S. EPA heavy-duty diesel aftertreatment compliance, DPF/SCR regulations, and NOx standards.
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