This DEF pressure sensor circuit sheet documents Detroit fault code SPN 4334 / FMI 4 on EPA10 engines, a failed-low condition with a 25% derate. It screens for related codes, then measures resistance to ground to separate shared wiring from a failed sensor.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD-Series (DD13, DD15, DD16) and Series 60 (DDEC VI) |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault code | SPN 4334 / FMI 4 |
| Fault name | Pressure sensor circuit failed low (DEF) |
| Emissions platform | EPA10 |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
| Source | TruckFaultCodes.com (© 2017); Detroit Power Service Literature |
DEF pressure sensor circuit sections covered
The two-page routine uses a multi-code check to catch shared shorts before the isolated resistance measurement.
- Monitored parameter and 25% engine derate; MIL and CEL
- Check for SPN 4334, 4335 and 3510 present together
- Repair the shared short to voltage or ground at ACM pin 84
- Disconnect the sensor and the ACM 120-pin connector
- Measure resistance to ground (less than 1K ohms)
- Repair the wire to ACM pin 100, or replace the sensor and verify ACM software
Applicable truck models
These steps cover Detroit DD-Series (DD13, DD15 and DD16) and Series 60 DDEC VI engines on the EPA10 platform with the ACM aftertreatment control module. Sensor removal follows the “Diesel Exhaust Fluid Pressure Sensor” chapter in Detroit Power Service Literature at the Detroit Diesel official website.
Who needs this DEF pressure sensor circuit manual
This pressure sensor circuit manual is for technicians clearing SPN 4334 / FMI 4, showing how a group of related codes points to shared wiring and when the ACM software level must also be verified.
The full 2-page PDF is available in the DiagTechPro manuals library; a free account is required to download. For workshop reference, Detroit documents the matching component removal and installation steps for SPN 4334 / FMI 4 in Power Service Literature, and technicians should keep the wiring pin numbers shown in this sheet on hand while testing on the bench.
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