The Detroit battery main switch document is a Detroit fault code reference that explains a missing J1939 BM message (Battery Main Switch), published for DD Series engines under SPN 511403 FMI 2 (GHG14). It gives workshop technicians the diagnostic sequence used to confirm the condition and return the truck to service, sourced from Detroit Power Service Literature.
Official document details
| Brand | Detroit (Detroit Diesel) |
| Model coverage | DD Series (EPA 2007-Current) and Series 60 (DDEC VI) |
| System / Group | Diagnostic Trouble Codes (DTCs) |
| Fault code | SPN 511403 / FMI 2 |
| Emissions family | GHG14 |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification — SPN 511403 / FMI 2
- J1939 Battery Main Switch message description
- Troubleshooting steps 1 to 6
- CPC4 and CAN line fault checks
- Clearing codes and releasing the vehicle
Troubleshooting the Detroit battery main switch code
The procedure connects a diesel diagnostic tool and checks for Common Powertrain Controller (CPC4) SPN 168 battery-voltage faults and Controller Area Network SPN 625 line faults, repairing those first. It then asks whether the CPC4 was recently reprogrammed and, after a five-minute power-down and ignition cycle, directs the technician to the SPN 625/FMI 9 PT CAN routine if the code is still active.
Applicable truck models and engines
This diagnostic sheet applies to Detroit DD Series diesel engines built to EPA 2007 through current emissions standards, and the covered fault also appears on Series 60 (DDEC VI) applications listed in the source. Confirm the exact engine family and calibration against the vehicle before making repairs, and cross-check the specifications on the official Demand Detroit website.
Who needs this battery main switch manual
Heavy-duty truck technicians, fleet maintenance staff and workshop owners diagnosing SPN 511403 FMI 2 with a diesel diagnostic tool will use this sheet to follow the correct steps rather than replacing parts by guesswork.
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