This DPF inlet pressure circuit guide is the Detroit DD Series SPN 3609 FMI 3 fault-code procedure for EPA07 engines, where the diesel particulate filter inlet reads failed high. It documents the voltage and resistance checks taken at the Motor Control Module.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD Series (EPA 2007-Current) |
| System / group | DD Series / DTCs |
| SPN | 3609 |
| FMI | 3 |
| Condition | inlet pressure circuit failed high |
| Emissions level | EPA07 |
| Source | Detroit Power Service Literature |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
DPF inlet pressure circuit checks
With the ignition on you check for SPN 3610/FMI, then measure voltage on pin 1 of the diesel particulate filter inlet sensor referenced to battery ground by the starter. Voltage present points to a short to power at MCM pin 114; no voltage points to an open feed. Later steps disconnect the MCM 120-pin connector and measure resistance across the sensor pins to confirm a short between MCM wires 85 and 118.
- Fault description: inlet reads failed high on EPA07 engines
- Steps 1 to 2 – Ignition on and check for multiple codes
- Steps 3 to 4 – Voltage on pin 1 versus battery ground
- Step 5 – Disconnect the inlet sensor connector
- Steps 6 to 8 – MCM 120-pin connector resistance and repair
Applicable truck models
This EPA07 fault code applies to Detroit DD Series heavy-duty diesel engines controlled by a Motor Control Module. Pin references follow Detroit Power Service Literature, so cross-check the engine wiring diagram on the official Detroit Diesel website.
Who needs this DPF inlet pressure circuit manual
Diesel technicians and workshop owners working on EPA07 Detroit engines use this document to decide between a short to power, an open feed, and a shorted signal wire before ordering parts. A diesel diagnostic tool and multimeter are required.
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