SPN 120 FMI 13 is a Detroit™ J1939-network diagnostic fault code, and this 1-page Detroit DD Series PDF documents the “J1939 Retarder Fluid Message Is Missing or Not Available” condition in full. This code reports a missing or unavailable J1939 retarder fluid message on the powertrain network. Diagnosis first rules out CPC4 battery-voltage codes (SPN 168) and an MCM2.1 CAN code (SPN 625/FMI 9) before checking module configuration. The summary below sets out the official causes, tools and troubleshooting order so a technician can verify the code before downloading the complete manual.
Official document details
| Brand | Detroit |
| Model coverage | DD Series (EPA 2007-Current) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Publication no. | Not printed on sheet (Detroit™ via TruckFaultCodes.com, © 2017) |
| Year / Revision | 2017 |
| Pages | 1 |
| File size | 0.2 MB |
| Format | |
| Language | English |
SPN 120 FMI 13 document contents
- Fault code identification (SPN and FMI)
- Multiple-code check (SPN 168, SPN 625/FMI 9)
- CPC4 reprogramming and configuration check
- ServiceLink module-communication review
Applicable truck models
The procedure applies to Detroit DD Series diesel engines on the GHG14 emissions platform that use a CPC4 Common Powertrain Controller and MCM2.1 on the J1939 network. It uses the diagnostic tool and ServiceLink. For factory service data, wiring diagrams and bulletins beyond this fault-code sheet, consult the official Detroit Diesel support site.
Who needs this SPN 120 FMI 13 manual
Technicians chasing a network or retarder-message complaint on a Detroit chassis need this sheet to separate a battery-voltage or CAN-line fault from a configuration error. It is aimed at drivability and electrical diagnosis.
The routine has you troubleshoot any battery-voltage or CAN codes first, confirm the CPC4 configuration after any reprogramming, then use ServiceLink to identify which modules are configured and their communication status.
The full 1-page PDF is available in the DiagTechPro manuals library; a free account is required to download it. Every document in the library is indexed by suspect parameter number and failure mode identifier, so you can cross-reference related Detroit DD Series fault codes without leaving the page.
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