This DEF metering air pressure sheet documents Detroit fault code SPN 4335 / FMI 3 on EPA10 engines, a sensor circuit-failed-high condition with a 25% derate. It screens for related codes, then reads harness voltage to separate a short to battery 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 4335 / FMI 3 |
| Fault name | DEF metering unit air pressure sensor circuit failed high |
| Emissions platform | EPA10 |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
| Source | TruckFaultCodes.com (© 2017); Detroit Power Service Literature |
DEF metering air pressure sections covered
The two-page routine uses a multi-code check before turning to the two voltage readings that split wiring from component.
- Monitored parameter and 25% engine derate; MIL and CEL
- Check for SPN 4335, 4334 and 3510 FMI 3 present together
- Repair the shared short to voltage or open at ACM2 pin 99
- Disconnect the sensor and turn the key on
- Read harness voltage (5.0v short, 4.75 to 4.9v normal)
- Repair the wire to ACM2 pin 74, or replace the sensor
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 ACM2 aftertreatment control module. Removal is described in the metering-unit air pressure sensor chapter of Detroit Power Service Literature at the Detroit Diesel official website.
Who needs this DEF metering air pressure manual
This metering air pressure manual helps technicians clear SPN 4335 / FMI 3 by reading the exact voltage thresholds, so a wiring short is repaired and a healthy sensor is left in place.
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 4335 / FMI 3 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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