SPN 101 FMI 2 — Crankcase Pressure Data Erratic
Erratic crankcase pressure signals are often caused by moisture or oil in the sense line rather than true blowby. Sensing-path proof — hose integrity and electrical checks — must be completed before CCV service or engine wear conclusions are drawn.
Fault Overview
SPN 101 FMI 2 indicates the crankcase pressure signal is unstable or implausible. Failing sensor, moisture or oil in the sense line, intermittent harness, and clogged or intermittently shifting CCV path are the primary causes. False crankcase pressure alarms from soaked sense lines is the most documented pattern.
Engine & Platform Coverage
Possible Causes
- 1.Moisture or oil in sense line creating intermittent pressure readings
- 2.Failing crankcase pressure sensor with intermittent output
- 3.Intermittent harness at sensor connector
- 4.Clogged or intermittently shifting CCV path affecting pressure readings
- 5.Sense-hose damage or kinking creating false pressure variations
Wiring & Circuit Notes
Inspect sense hose and port for moisture, oil accumulation, or kinking. Check sensor connector integrity. Verify harness routing does not allow sense-line moisture to reach the sensor.
DVOM Specs & Sensor Tests
Correlate PID readings with physical symptoms — oil pushes from breather, filter bag inflation, or visible crankcase pressure evidence. Abrupt electrical dropouts are electrical; gradual pressure changes that correlate with physical symptoms are more likely to be true crankcase pressure variations. Measure crankcase pressure directly when possible to confirm true versus false readings.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Inspect sense hose and port for moisture, oil accumulation, or kinking
- 2Check sensor connector integrity and harness routing
- 3Perform electrical checks on sensor circuit
- 4Correlate PID with physical symptoms — oil pushes, breather activity
- 5Inspect CCV path for restriction or contamination
- 6Measure crankcase pressure directly when possible before engine wear conclusions
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
4 steps locked- 1Inspect sense hose and port for moisture, oil accumulation, or kinking
- 2Check sensor connector integrity and harness routing
- 3Perform electrical checks on sensor circuit
- 4Correlate PID with physical symptoms — oil pushes, breather activity
- 5Inspect CCV path for restriction or contamination
- 6Measure crankcase pressure directly when possible before engine wear conclusions
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
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Summary
SPN 101 FMI 2 is often a sensing-line or CCV-related fault. Sense-hose inspection, electrical checks, and physical symptom correlation precede any engine wear conclusions.