SPN 102 FMI 3 — Intake Manifold Pressure Circuit Voltage Above Normal
MAP circuit high-voltage codes are electrical open diagnostics first. Underboost and overboost investigations driven purely by an open MAP circuit are the most documented misdiagnosis pattern. The turbocharger and boost system are not indicated until the MAP sensor circuit is proven.
Fault Overview
SPN 102 FMI 3 indicates the intake manifold pressure (MAP or boost) sensor circuit voltage is above the normal maximum — an open circuit or high-signal class fault. Open signal wire, failed sensor, unplugged connector, and 5V or ground anomalies are the primary causes. Underboost and overboost investigations driven by an open MAP circuit is the most documented misdiagnosis.
Engine & Platform Coverage
Possible Causes
- 1.Open signal wire from heat or vibration damage near intake manifold
- 2.Failed MAP sensor — open internal element
- 3.Unplugged or loose connector at intake manifold sensor location
- 4.5V reference supply anomaly affecting sensor output
- 5.Ground anomaly at sensor ground circuit
- 6.Chafed harness near brackets on intake manifold
Wiring & Circuit Notes
Inspect sensor connector at the intake manifold — chafe near brackets is common at this location. Check shared 5V bus health — a 5V reference anomaly can affect multiple sensors simultaneously. Verify ground integrity at the sensor ground circuit.
DVOM Specs & Sensor Tests
KOEO MAP reading should be near atmospheric baseline when the sensor is healthy. An open or high electrical value at KOEO confirms a circuit fault — the sensor cannot read below atmospheric without boost. Verify reference, ground, and signal at the sensor connector before boost system conclusions.
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Verify 5V reference and ground at MAP sensor connector
- 2Check signal wire continuity from sensor to ECM
- 3Inspect connector for damage or loose lock
- 4Inspect harness for chafe near intake manifold brackets
- 5Replace MAP sensor after circuit is proven clean
- 6Proceed to boost performance diagnosis only after MAP circuit is confirmed functional
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
4 steps locked- 1Verify 5V reference and ground at MAP sensor connector
- 2Check signal wire continuity from sensor to ECM
- 3Inspect connector for damage or loose lock
- 4Inspect harness for chafe near intake manifold brackets
- 5Replace MAP sensor after circuit is proven clean
- 6Proceed to boost performance diagnosis only after MAP circuit is confirmed functional
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.
Start Diagnosing This Fault Now
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Summary
SPN 102 FMI 3 is an electrical open diagnosis at the MAP sensor circuit. Reference, ground, and signal integrity must be proven before any boost system work is considered.