SPN 168 FMI 9 is the Detroit DD Series diagnostic trouble code for battery connection lost, and this page documents its official engine charging and battery power circuit troubleshooting sheet. The three-page sheet moves from alternator and battery checks into detailed resistance and voltage-drop measurements on the Motor Control Module (MCM) and Common Powertrain Controller (CPC) power and ground circuits.
SPN 168 FMI 9 document details
| Brand | Detroit |
| Model coverage | DD Series — DD13, DD15, DD16 |
| System / group | DD Series (EPA 2007-Current) / DTCs |
| SPN | 168 |
| FMI | 9 |
| Fault | Battery Connection Lost |
| Emissions / revision | GHG14 — Copyright 2017 |
| Pages | 3 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- Fault description: battery connection lost
- Alternator and battery checks
- Ground-circuit resistance (MCM 21/5-21/9, CPC 2/2)
- Power-circuit resistance (MCM 21/11-21/15, CPC 2/1)
- Current-drop tests on power and ground wires
Troubleshooting steps summarised
After confirming the alternator drive belt, mounting, operation and battery charge, the technician measures the resistance of the individual ground-circuit wires at MCM 21/5, 21/6, 21/8, 21/9 and CPC 2/2, then the power-circuit wires at MCM 21/11, 21/12, 21/14, 21/15 and CPC 2/1 with the engine running above 12.5 V. Any wire over 0.5 ohms, or any voltage drop above 0.2 volts under the current-drop tests, is repaired or replaced.
Applicable truck models covered
It covers Detroit DD Series engines (DD13, DD15 and DD16) with GHG14 emissions hardware using the MCM and CPC power and ground architecture. For engine specifications and warranty coverage, refer to the official Demand Detroit service resources. These troubleshooting steps are cross-checked with the Detroit Diesel Diagnostic Link (DDDL) and the official Demand Detroit service resources.
Who needs this SPN 168 FMI 9 guide
Technicians diagnosing an intermittent lost battery connection, high-resistance ground, or voltage-drop fault on the module power feeds use this sheet to pinpoint the failing wire before replacing a controller.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download the complete step-by-step document.
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