SPN 3660 FMI 4 is the Detroit DD Series diagnostic trouble code stored when the Motor Control Module (MCM) detects an injector cylinder #2 amplifier control valve abnormal operation (minimum) on cylinder #2. This manual page reproduces the official Detroit troubleshooting sequence, the monitored parameter and the engine reaction so a technician can trace the fault to the injector, the fuel injector wiring harness or the MCM. It is written for workshops running the Detroit Diesel Diagnostic Link.
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | DD Series (EPA 2007-Current) and Series 60 (DDEC VI – EPA 2007) |
| System / Group | DTCs / diagnostic trouble codes |
| Emission platform | EPA10 / GHG14 |
| Dash lamps | MIL, CEL |
| Engine reaction | Derate 25% |
| Pages | 6 |
| File size | 0.5 MB |
| Format | |
| Language | English |
What the SPN 3660 FMI 4 manual covers
The procedure in this manual walks through the following checks:
- Fault description and the monitored amplifier control valve parameter
- Typical enabling conditions, execution frequency and the verification RPM range
- Step 1 check for related codes SPN 168 and SPN 723
- Front fuel injector harness 14-pin connector and seal inspection
- Injector resistance measurement charts on the valve-cover side
- Rocker cover removal and two-piece fuel injector wiring harness checks
- MCM 120-pin connector resistance test and test-MCM installation
Applicable Detroit truck models
This fault code applies to Detroit DD Series engines on the EPA 2007-Current platform and to Series 60 engines equipped with DDEC VI, exactly as listed in the source document. The full resistance charts and component removal steps reference Detroit Power Service Literature, including removal of the two-piece fuel injector wiring harness and the rocker cover. For engine identification and service bulletins, consult the official Detroit Diesel support site.
Who needs this SPN 3660 FMI 4 guide
Diesel technicians and fleet maintenance shops that find a fault on the injector amplifier control valve need this 3660 FMI 4 guide to confirm whether the problem lies in the fuel injector, the two-piece injector wiring harness or the MCM before any part is replaced. Following the resistance checks in order prevents unnecessary injector changes.
Related manuals library
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
