SPN 4374 FMI 4 is the Detroit Diesel diagnostic trouble code set when the DEF pump speed signal reads below its measurement range on DD Series (EPA 2007-current) engines. This 3-page troubleshooting sheet lists the fault definition, the relevant monitor or note data, and a numbered diagnostic routine that ends in the correct wiring or component repair. It is drawn from TruckFaultCodes.com (© 2017) and applies to the GHG14 emissions calibration.
Official document details
| Brand | Detroit Diesel |
|---|---|
| Model coverage | DD Series engines (EPA 2007-current) |
| System / group | DTCs — DEF pump speed circuit |
| Suspect parameter (SPN) | SPN 4374 |
| Failure mode (FMI) | DEF pump speed signal below range |
| Emissions calibration | GHG14 |
| Verification | SCR ADS self-check |
| Source / copyright | TruckFaultCodes.com, © 2017 |
| Pages | 3 |
| File size | 0.2 MB |
| Format / language | PDF / English |
SPN 4374 FMI 4 table of contents
After confirming no other codes are stored, the DEF pump harness and connector are inspected for chafing and pin damage. A series of resistance checks follows: DEF pump pin 1 to ACM pin 95 (less than five ohms), pin 1 to ground (greater than 10K ohms), and pins 1-to-2, 1-to-3 and 1-to-4 (each greater than 10K ohms) to find opens and shorts. If all readings pass, a test ACM2.1 is installed; a returning fault leads to replacing the DEF pump, verified with the SCR ADS self-check routine.
- Fault code header and log-file note
- Troubleshooting steps 1 to 12
- DEF pump four-pin connector pin-out
- Resistance decision points (open and short isolation)
- DEF pump or ACM2.1 replacement and SCR ADS verification
Applicable truck models
This sheet is part of the DD Series diagnostic trouble code library and addresses the DEF pump speed feedback circuit. The SPN 4374 FMI 4 procedure applies to Detroit DD Series (EPA 2007-current) engines running the GHG14 calibration, and the same code index is cross-referenced under the Detroit Series 60 (DDEC VI, EPA 2007) fault-code set. For engine identification and warranty details, see the Detroit Diesel official site.
Who needs this 4374 FMI 4 manual
It is intended for diesel technicians tracing a low DEF pump speed signal and the wiring behind it on Detroit DD Series engines. The step-by-step resistance targets make it clear whether the harness, the pump or the aftertreatment control module is at fault.
The full 3-page PDF is available in the DiagTechPro manuals library; a free account is required to download.
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