Detroit DD13 SPN 84 FMI 3 – MCM Vehicle Speed Sensor Open Circuit

This guide provides instructions for troubleshooting and resolving the Detroit DD13 engine fault code SPN 84 FMI 3, indicating an open circuit in the MCM Vehicle Speed Sensor (VSS).

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Fault Description

• Code: SPN 84 FMI 3
• Description: Vehicle Speed Sensor circuit failed high (open circuit).

Monitored Parameter

• Vehicle Speed Sensor (VSS)

Enabling Conditions

• Always enabled

Monitor Sequence

• None

Execution Frequency

• Always enabled

Typical Duration

• 2 seconds

Dash Lamps

• MIL (Malfunction Indicator Lamp)

Engine Reaction

• None

Verification Procedure

• Allow engine to idle for 1 minute.

Probable Causes

1. Faulty vehicle speed sensor
2. Damaged or open wiring between vehicle speed sensor and ECM

Recommended Actions

1. Inspect the vehicle speed sensor for damage, contamination, or loose connections.
2. Check the wiring harness between the VSS and ECM for continuity, corrosion, or breaks.
3. Replace the vehicle speed sensor if confirmed faulty.
4. Repair or replace wiring as necessary.
5. Clear fault codes and verify proper operation.

More repair cases for Detroit Diesel engines,please refer to:Detroit Diesel Engine Repair