SPN 158 FMI 7 is a Detroit™ aftertreatment diagnostic fault code, and this 2-page Detroit DD Series PDF documents the “Battery Power Disconnected Before ACM Completed the DEF Key-Off Purge Cycle” condition in full. This is a silent fault with no dash lamps: it sets if battery power is disconnected before the Aftertreatment Control Module (ACM) has finished the Diesel Exhaust Fluid key-off purge cycle. If the fault occurs while the engine is running, all power and grounds from the batteries to the ACM should be inspected. 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 | 2 |
| File size | 0.3 MB |
| Format | |
| Language | English |
SPN 158 FMI 7 document contents
- Fault code identification (SPN and FMI)
- Silent-fault description (no dash lamps)
- Power and ground inspection note
- Two-step troubleshooting procedure
- Clear fault and release vehicle
Applicable truck models
The condition applies to Detroit DD Series engines on EPA10 and GHG14 emissions platforms equipped with an Aftertreatment Control Module and Diesel Exhaust Fluid dosing. The short procedure only requires the diesel diagnostic tool. For factory service data, wiring diagrams and bulletins beyond this fault-code sheet, consult the official Detroit Diesel support site.
Who needs this SPN 158 FMI 7 manual
Technicians who see this code after a battery, starter or wiring job need this sheet to understand that it is usually a byproduct of an interrupted purge cycle rather than a hardware failure. It saves unnecessary aftertreatment parts replacement.
The two-step routine has you start and idle the engine for one minute, switch the ignition off and wait five minutes for the purge cycle to complete, then key on, clear the fault and release the vehicle.
The full 2-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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