This 5V sensor supply low sheet explains Detroit SPN 3509 FMI 4, raised when the Motor Control Module reads a short to ground below 4.7 volts on the bank 1 reference. It names the sensors on that circuit so the harness can be inspected and repaired. It is a concise reference rather than a long step procedure.
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | DD Series (EPA 2007-Current); also filed under Series 60 (DDEC VI – EPA 2007) |
| System / Group | DTCs — 5V Sensor Supply Bank 1 Circuit Failed Low |
| Fault code | SPN 3509 / FMI 4 |
| Source | www.TruckFaultCodes.com (© 2017) |
| Pages | 1 |
| File size | 0.2 MB |
| Format | |
| Language | English |
5V sensor supply low diagnostic guide
The sheet lists the MCM pins tied to the affected reference: pin 58 feeds the charge air cooler (CAC) outlet pressure sensor and the fuel rail pressure sensor, while pin 117 feeds the EGR delta P sensor and the intake throttle valve. The instruction is to inspect the harness for a short to ground on those branches, repair as necessary and verify the fix. It is a wiring-focused document for a low reference reading.
Document table of contents
- Fault code identification: SPN 3509, FMI 4
- Fault condition: reference shorted to ground below 4.7 volts
- MCM pin-to-sensor reference chart
- Harness inspection and repair guidance
Applicable truck models
This procedure applies to Detroit DD Series engines built for EPA 2007 and later, covering EPA07 calibrations as printed on the document cover, and the identical SPN/FMI sheet is also filed under Detroit Series 60 (DDEC VI, EPA 2007). Confirm the emissions platform on your truck and cross-check the connector and pin numbers against the official Detroit engine support site before making any repair.
Who needs this 5V sensor supply low manual
An electrical technician on an EPA07 Detroit engine uses this reference to trace a grounded reference wire across the CAC outlet pressure, fuel rail pressure, EGR delta P and intake throttle valve branches before replacing any sensor.
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