SPN 656 FMI 14 is the Detroit DD Series diagnostic fault code that identifies Injector cylinder #6 needle control valve abnormal operation. This DiagTechPro reference summarizes the official 6-pages Detroit diagnostic sheet so a technician can confirm the condition before opening the truck, and it links to the full downloadable PDF.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD Series (EPA 2007-Current) diesel engines |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault condition | Injector cylinder #6 needle control valve abnormal operation |
| Published source | TruckFaultCodes.com, Copyright © 2017 |
| Pages | 6 |
| File size | 0.5 MB |
| Format | |
| Language | English |
SPN 656 FMI 14 diagnostic overview
This Detroit EPA07 sheet covers the injector cylinder #6 needle control valve abnormal operation. The technician checks for related SPN 168 or 723 codes, warms the engine above 71°C (160°F), and inspects the rear fuel injector harness 14-pin connector for water or oil intrusion and bent pins. Resistance is measured on the harness and, after removing the rocker cover, on the one-piece fuel injector wiring harness for the three-filter system; the checks continue at the Motor Control Module (MCM) 120-pin connector, with a test MCM installed using extension harness J-49120.
Document table of contents
- Fault code identification
- Multiple-code check
- Rear fuel injector harness 14-pin inspection
- Resistance measurements and test MCM
- MCM replacement reference
Applicable truck models covered
This diagnostic applies to Detroit DD Series EPA07 diesel engines and is grouped under the Series 60 (DDEC VI – EPA 2007) DTCs. It covers cylinder #6 fuel injection on the one-piece three-filter fuel injector wiring harness. For the OEM wiring schematics referenced in this procedure, see the official Detroit engine manufacturer site.
Who needs the SPN 656 FMI 14 manual
Workshop technicians and fleet owners using the diesel diagnostic tool to read Detroit fault codes and test the needle control valve and Motor Control Module wiring will need this sheet. The full step-by-step PDF is available in the DiagTechPro manuals library, and a free account is required to download it.
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