SPN 1073 FMI 4 is the Detroit DD Series fault-code troubleshooting sheet that documents a Jake Brake Stage 2 circuit failed low condition, which illuminates the MIL and CEL lamps and applies a 25% engine derate on the Motor Control Module engine platform. This 2-page reference reproduces the fault-code identification and the factory decision tree so a technician can diagnose the concern before replacing parts.
Official document details — SPN 1073 FMI
| Brand | Detroit |
|---|---|
| Model coverage | Detroit DD Series (EPA 2007-Current) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault code | FMI 4 under SPN 1073 (ALL YEARS) |
| Source | Detroit fault-code literature via TruckFaultCodes.com, © 2017 |
| Pages | 2 |
| Format | |
| Language | English |
SPN 1073 FMI 4 fault description
This two-page sheet isolates a short to ground in the stage-2 engine-brake circuit. The technician disconnects the rear two-piece fuel injector wiring harness and measures resistance from pin 13 to ground, expecting more than 15 ohms; a lower reading identifies a short to ground toward pin 32 of the Motor Control Module (MCM) 120-pin connector. If that check passes, the rocker cover is removed and resistance is measured from a Jake Brake solenoid terminal to ground, resolving the fault to either the solenoid or a short in the front fuel injector valve-cover harness.
The SPN 1073 FMI 4 sheet identifies the following likely causes and check points:
- Short to ground between pin 13 of the harness and pin 32 of the MCM
- Failed rear Jake Brake solenoid
- Short in the front fuel injector valve-cover harness
Document table of contents
- Description and monitored conditions
- Harness resistance-to-ground check
- Rocker cover removal
- Jake Brake solenoid measurement
Service tools referenced
- J-48671-10 test adapter
Applicable truck models
This troubleshooting sheet applies to Detroit DD Series engines built from EPA 2007 to current that use the Motor Control Module (MCM) and Common Powertrain Controller architecture. Confirm the engine’s emissions family and calibration against the manufacturer’s official documentation at the Detroit engine website before repairs.
Who needs this SPN 1073 FMI 4 manual
Heavy-duty diesel technicians, fleet shops and mobile mechanics who retrieve this code on a Detroit DD engine need this manual to follow the factory decision tree instead of guessing. It is written for anyone using DDDL or an equivalent diesel diagnostic tool who wants the exact test values before condemning a component.
The full 2-page PDF of this procedure is available in the DiagTechPro manuals library; a free account is required to download.
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