SPN 102 FMI 0 — Intake Manifold Pressure Above Normal (Overboost)
Overboost codes still start with MAP validity and actuator response. Unnecessary turbo replacement for MAP open or high circuit conditions is the most documented misdiagnosis on this fault class.
Fault Overview
SPN 102 FMI 0 indicates MAP or boost pressure is above the calibrated maximum. Actuator stuck toward closed vanes, control faults, MAP sensor bias high, cold binding, and oil control issues on some VGT designs are the primary causes. MAP sensor proof and actuator command-response correlation are required before any turbo replacement.
Engine & Platform Coverage
Symptoms
- •Overboost code active
- •MAP reading above maximum on scan tool
- •Actuator not responding to open-vane command
- •Overboost event in cold conditions
- •Turbo replaced without resolving overboost
Possible Causes
- 1.Actuator stuck toward closed vanes — carbon or mechanical binding
- 2.Control faults preventing open-vane command from reaching actuator
- 3.MAP sensor bias high producing false overboost reading
- 4.Cold binding of VGT mechanism
- 5.Oil control issues on oil-controlled VGT actuator designs
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
3 steps locked behind Technician Mode- 1Step 1 — Sensor Proof: Verify MAP sensor accuracy. KOEO MAP should read near atmospheric pressure. An electrically pegged MAP reading without mechanical overboost confirms a sensor or circuit fault.
- 2Step 2 — Desired vs Actual Boost Correlation: Correlate MAP with actuator position and desired boost. If MAP is high while the actuator is commanded to open vanes, the actuator is not responding or the vanes are mechanically stuck.
- 3Step 3 — Actuator Freedom and Response: Command the actuator to the open-vane position and observe actual position response. Inspect for mechanical binding or carbon packing in the VGT mechanism.
- 4Step 4 — Turbo Path Last: Proceed to turbo replacement only after MAP sensor is proven accurate, actuator is proven to respond correctly, and mechanical seizure is confirmed as the cause.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Replace MAP sensor after bias high is confirmed.
- 2Replace or repair actuator after non-response to open-vane command is confirmed.
- 3Address oil supply issues to actuator on applicable designs.
- 4Replace turbo assembly only after geometry seizure is confirmed.
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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Related Resources
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Summary
SPN 102 FMI 0 is an overboost fault. Prove MAP sensor accuracy and actuator response before any turbo replacement.