SPN 2659 FMI 0 — EGR Mass Flow Rate – Above Normal, Most Severe (EGR flow target error, high flow) — Detroit DD15

Measured EGR flow is above the target on Detroit DD15 (2010–present).

Updated October 15, 2026

What it means

SPN 2659 is EGR Mass Flow Rate. FMI 0 means the measured value is above normal, most severe. On Detroit DD15 the EGR system is cooled EGR with an EGR valve and EGR flow measurement (delta pressure). The code indicates the controller sees EGR flow higher than the commanded target.¹

Most likely causes

1. EGR valve stuck open or not closing fully — Mechanical binding or soot buildup keeps the EGR valve open, raising measured flow above target.¹
2. EGR delta pressure sensor fault or signal error — A faulty delta-pressure sensor or wiring can report an artificially high flow reading, triggering the high-flow fault.¹
3. EGR delta pressure sensor lines plugged or leaking — Blocked or leaking pressure tubes give incorrect differential pressure readings, causing the controller to calculate excessive EGR flow.¹

How to diagnose

1. Verify the code is active in MCM/ACM/CPC and note freeze-frame conditions (engine speed, load, coolant temp).
2. Inspect EGR valve operation and position feedback; check for sticking, carbon buildup, or mechanical binding that prevents full closure.
3. Inspect EGR delta pressure sensor, its electrical connector, and the pressure tubes for blockage, leaks, or damage; clear or replace tubes as needed.
4. Compare live EGR flow data and delta-pressure readings to expected values at idle and under load; look for flow above target with valve commanded closed.
5. Check for related EGR or intake faults that could affect flow calculation; address any accompanying codes before condemning the EGR valve.

Common mistake to avoid

Replacing the EGR valve without testing it. If the valve still moves freely, a carbon cleaning often fixes the flow code; and if it opens on command but the code stays, the blockage is in the passages or cooler, not the valve. Source: FleetRabbit — EGR valve problems and repair.

Parts and tools you may need

• Diagnostic scan tool capable of Detroit MCM/ACM/CPC J1939 data
• EGR valve cleaning kit and approved solvents
• Replacement EGR delta pressure sensor and pressure tubes
• Basic hand tools and safety equipment

Tools you’ll need

• diagnostic scan tool — Reads SPN 2659 FMI 0 and freeze-frame data from the Detroit DD15 MCM/ACM to confirm active conditions and EGR commanded vs actual values.
• digital multimeter — Checks EGR delta pressure sensor supply, ground, and signal voltages to rule out electrical faults causing an over-range flow reading.
• manometer — Measures actual EGR delta pressure across the orifice to verify the sensor reading and detect plugged or leaking pressure tubes.
• borescope — Inspects EGR valve seat and passages for carbon buildup or sticking that prevents full closure and causes excessive flow.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $140–$200 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

High-pressure fuel injection systems are safety-critical. If diagnosis points to internal EGR cooler or valve replacement, have a qualified diesel technician perform the work.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources