SPN 4259 FMI 3 is the Detroit diesel diagnostic trouble code for the Fuel Injector 4, 5 or 6 Amplifier Control Valve Circuit Short to Battery on DD Series (EPA 2007-Current) engines. This 2 pages ALL YEARS PDF documents the code description, monitored parameters, dash-lamp and engine-reaction data, and the diagnostic routine drawn from Detroit Power Service Literature.
What SPN 4259 FMI 3 means
This code identifies a short to battery or power on the amplifier control valve circuit for rear fuel injectors 4, 5 or 6. Diagnosis is a wiring test between the rear fuel injector harness and the 120-pin MCM connector.
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | DD Series (EPA 2007-Current), also cross-referenced on Series 60 (DDEC VI, EPA 2007) |
| System / group | Diagnostic trouble codes (DTCs) |
| Fault code | SPN 4259 / FMI 3 (ALL YEARS) |
| Monitored parameter | Injector amplifier control valve, cylinders 4, 5 and 6 |
| Pages | 2 pages |
| Source | Detroit Power Service Literature |
| Format | PDF, English |
Diagnostic steps in this manual
The manual isolates the short with voltage checks at the harness connector.
- Disconnect the rear fuel injector harness 14-pin connector and turn the ignition on with the engine off.
- Measure the voltage at pin 1 on the MCM side of the 14-pin connector to ground.
- Voltage present means a short to power toward pin 4 of the 120-pin MCM connector must be repaired.
- With no voltage, check pins 8 and 12 of the harness against pins 8 and 6 of the 120-pin MCM connector.
All pin references follow the Detroit 120-pin MCM connector layout documented in Power Service Literature. Because SPN 4259 FMI 3 is a factory-defined code, following the exact fuel injector amplifier control valve circuit sequence and the Detroit Power Service Literature references is what keeps the repair verifiable.
Applicable trucks and engines
This procedure applies to Detroit DD Series diesel engines built to EPA 2007 and later standards, and Detroit cross-references the same code on Series 60 (DDEC VI, EPA 2007) engines. Confirm exact coverage on the Detroit Diesel official website.
Who needs this SPN 4259 FMI 3 guide
Heavy-duty technicians and workshop owners diagnosing rear fuel injector harness problems use this guide to follow the factory troubleshooting steps instead of guessing. The full PDF is available in the DiagTechPro manuals library, with a free account required to download.
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