SPN 556 FMI 9 is a Detroit fault code reference sheet that documents the J1939 RC message from the transmission retarder is missing diagnostic for DD Series engines built to EPA 2007 and later emissions standards. This single-topic page reproduces the factory-style test order Detroit dealers and independent shops follow for the transmission retarder J1939 message, from confirming related codes through to the final repair decision.
Official document details
| Brand | Detroit |
| Model coverage | DD Series (EPA 2007-Current) |
| System / group | Diagnostic Trouble Codes (DTCs) |
| Suspect Parameter Number | 556 |
| Failure Mode Identifier | 9 |
| Emissions revision | GHG14 |
| Source | Detroit fault code sheet (© 2017, www.TruckFaultCodes.com) |
| Pages | 1 |
| File size | 0.22 MB |
| Format | |
| Language | English |
SPN 556 FMI 9 troubleshooting steps
The sheet lists the ordered checks Detroit publishes for this code, so a technician can rule out network and power-supply faults before condemning a switch, sensor or module. The main steps are:
- Note that this fault can set during transmission module reprogramming; if it occurs while programming, clear the code and release the vehicle.
- Check whether Common Powertrain Controller (CPC) codes SPN 168 / FMI 0, 14 or 18 (battery voltage) are present, and repair those first.
- Check whether Motor Control Module (MCM) SPN 625 / FMI 9 is present; if so, repair the Controller Area Network (CAN) line.
- Use the diesel diagnostic tool to see which modules are configured and their communication status, then follow the affected module’s procedure.
Applicable truck models
This code applies to Detroit DD Series diesel engines (EPA 2007 to current) and, for the shared driveline codes, to Series 60 (DDEC VI) installations that use the same Common Powertrain Controller and Motor Control Module architecture. Coverage is defined by the engine and control-module configuration rather than the truck badge, so confirm the exact build against the current model line on the Detroit Diesel official website.
Who needs this SPN 556 FMI 9 manual
This SPN 556 FMI 9 manual is written for diesel technicians and DD Series fleet owners who are diagnosing a missing transmission retarder message on the J1939 bus and want the exact Detroit test order before ordering parts. Following the documented sequence keeps unnecessary sensor and module replacements to a minimum.
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