Detroit DD13 EPA07 (2007-09) Fault Code: SPN 94 FMI 3 (MCM) – Fuel Compensation Pressure Sensor Circuit Failed High

Detroit DD13 EPA07 (2007–09) – SPN 94 FMI 3 (MCM): Fuel Compensation Pressure Sensor Circuit Failed High

Fault Code Overview

Fault Code Description

SPN 94 FMI 3 is set by the Motor Control Module (MCM) when the fuel compensation pressure sensor signal voltage rises above the maximum expected threshold. The fuel compensation pressure sensor monitors the low-pressure (supply) side of the fuel system. A failed-high signal indicates a short to voltage in the signal wire, an open ground/return circuit, or a failed sensor.

Note: Please see the step-by-step troubleshooting procedures for this specific code.

Probable Causes

1. If fault codes 100-3, 4077-3, and 94-3 are also present, repair the wiring between pin 82 of the ECM connector and the engine oil pressure, fuel line, and fuel compensation pressure sensors.
2. If fault codes 4407-3 and 94-3 are present, repair the wiring between pin 104 of the ECM connector and the fuel line and fuel compensation pressure sensor.
3. Failed fuel compensation pressure sensor.
4. Fuel compensation pressure sensor harness/connector fault.

Symptoms

• Amber warning lamp illuminated on the dash
• SPN 94 FMI 3 logged in the MCM fault memory
• Possible engine derate or power reduction
• Fuel compensation pressure reading above normal range in DDDL live data

Diagnostic Steps

1. Connect diagnostic software (Detroit Diesel DiagnosticLink / DDDL) and confirm the active fault code SPN 94 FMI 3 in the MCM. Note all other active fault codes present.
2. Check for companion codes — if 100-3, 4077-3, and 94-3 are all active, the shared 5V supply wire at ECM pin 82 is likely shorted to voltage or open. Inspect and repair the wiring to all three sensors on that circuit.
3. Check for companion codes — if 4407-3 and 94-3 are active together, inspect the wiring at ECM pin 104 shared between the fuel line and fuel compensation pressure sensors. Repair as needed.
4. Inspect the sensor connector — check for corrosion, moisture, bent or pushed-back pins, and loose fit. Clean and reseat the connector. Apply dielectric grease if needed.
5. Measure the signal wire voltage — with the sensor connected and key on, back-probe the signal pin. A reading significantly above 5V indicates a short to voltage. With the sensor disconnected, if the signal wire still reads high, the short is in the harness. Locate and repair.
6. Check the sensor ground circuit — measure resistance from the sensor ground pin at the harness connector to chassis ground. High resistance or open circuit indicates a broken ground wire. Repair as needed.
7. Test the fuel compensation pressure sensor — measure resistance across the sensor terminals and compare to the specification in the Detroit DD13 service manual. Replace the sensor if out of spec.
8. Inspect the harness — trace the sensor wiring from the fuel filter/pump area to the MCM connector. Look for chafing, pinched wires, or insulation damage causing a short to voltage. Repair as needed.
9. Clear the fault code and perform a key cycle. Monitor the fuel compensation pressure signal in DDDL live data to confirm the circuit is operating within the normal voltage range.
10. Replace the MCM only if all wiring, connector, and sensor checks pass and the fault persists.

Related Fault Codes

• SPN 94 FMI 4 – Fuel Compensation Pressure Sensor Circuit Failed Low
• SPN 94 FMI 1 – Fuel Supply Pressure Low – Mechanical
• SPN 100 FMI 3 – Engine Oil Pressure Sensor Circuit Failed High
• SPN 4077 FMI 3 – Fuel Line Pressure Sensor Circuit Failed High
• SPN 4407 FMI 3 – Fuel Line Pressure Sensor Circuit Failed High

Recommended Tools

• Detroit Diesel DiagnosticLink (DDDL) software
• Digital multimeter
• Wiring diagram for Detroit DD13 EPA07
• RP1210-compliant diagnostic adapter (Nexiq USB Link, Noregon DLA+, etc.)

Always refer to the official Detroit Diesel service documentation and wiring diagrams for your specific vehicle configuration before performing repairs.