SPN 1180 FMI 2 — Turbocharger Turbine Inlet Temperature Data Erratic
Erratic turbine inlet temperature is usually probe and harness integrity under heat and vibration. Intermittent derate or thermal strategy instability from one failing turbine inlet EGT is the most documented consequence.
Fault Overview
SPN 1180 FMI 2 indicates the turbocharger turbine inlet temperature data is unstable or implausible — an erratic or data-validity class fault. Failing probe, intermittent harness, connector fretting, and heat-zone brittle wiring are the primary causes. Abrupt dropouts in the turbine inlet EGT PID during steady load are electrical; compare with related EGT and boost behavior to distinguish electrical from mechanical causes.
Engine & Platform Coverage
Possible Causes
- 1.Failing turbine inlet EGT probe with intermittent internal element
- 2.Intermittent harness from heat-zone brittleness near turbine housing
- 3.Connector fretting at turbine inlet sensor connector
- 4.Heat-zone brittle wiring with intermittent continuity under thermal cycling
- 5.Vibration-induced intermittent open at harness clips near turbine housing
Wiring & Circuit Notes
Hot wiggle tests at the turbine inlet sensor and nearest harness clips are the most productive diagnostic step for SPN 1180 FMI 2. Graph the turbine inlet EGT PID during steady load — abrupt dropouts are electrical; compare with related EGT and boost behavior.
DVOM Specs & Sensor Tests
Graph turbine inlet EGT PID during steady load. Abrupt dropouts to extreme cold or irrational values are electrical — they differ from smoother mechanical temperature changes. Perform hot wiggle tests at the sensor connector and nearest harness clips while monitoring the PID. Continuity check the signal wire under thermal cycling if possible. Replace the sensor and pigtail/harness after the intermittent source is identified.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Graph turbine inlet EGT PID during steady load — identify abrupt dropout pattern
- 2Perform hot wiggle tests at turbine inlet sensor connector and nearest harness clips
- 3Check continuity of signal wire under thermal cycling if possible
- 4Inspect connector for fretting and heat-zone harness for brittleness
- 5Replace turbine inlet EGT sensor and pigtail/harness after intermittent source is identified
- 6Verify stable EGT tracking after repair before returning to service
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
4 steps locked- 1Graph turbine inlet EGT PID during steady load — identify abrupt dropout pattern
- 2Perform hot wiggle tests at turbine inlet sensor connector and nearest harness clips
- 3Check continuity of signal wire under thermal cycling if possible
- 4Inspect connector for fretting and heat-zone harness for brittleness
- 5Replace turbine inlet EGT sensor and pigtail/harness after intermittent source is identified
- 6Verify stable EGT tracking after repair before returning to service
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
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Summary
SPN 1180 FMI 2 is an intermittent turbine inlet EGT probe and harness integrity diagnosis. Hot wiggle tests and PID graphing under load are required before any turbo hardware conclusions.