This DEF dosing unit circuit guide is the Detroit DD Series SPN 3597 FMI 4 fault-code procedure for GHG14 engines, where high side digital output 1 reads failed low. It documents the resistance checks taken at the Diesel Exhaust Fluid dosing harness.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD Series (EPA 2007-Current) |
| System / group | DD Series / DTCs |
| SPN | 3597 |
| FMI | 4 |
| Condition | high side digital output 1 circuit failed low |
| Emissions level | GHG14 |
| Source | Detroit Power Service Literature |
| Pages | 2 |
| File size | 0.3 MB |
| Format | |
| Language | English |
DEF dosing unit circuit checks
After turning the ignition off you disconnect the Diesel Exhaust Fluid dosing harness connector and inspect it for bent, spread or corroded pins. Resistance between pins 4 and 7 above ten thousand ohms sends you on to check pin 4 against battery ground, separating a short between the pins from a short to ground at pin 3, or a shorted wire back to pin 3 of the ACM2.1 120-pin connector.
- Fault description: high side digital output 1 circuit failed low
- Steps 1 to 3 – Ignition off, disconnect harness, inspect pins
- Step 4 – Disconnect the ACM2.1 120-pin connector
- Step 5 – Resistance between pins 4 and 7
- Step 6 – Resistance between pin 4 and battery ground
Applicable truck models
This GHG14 fault code applies to Detroit DD Series diesel engines fed from the ACM2.1 aftertreatment module. The harness pinout follows Detroit Power Service Literature; confirm it against the engine build on the official Detroit Diesel website.
Who needs this DEF dosing unit circuit manual
Diesel technicians and workshop owners diagnosing a low-side dosing fault on a GHG14 Detroit engine use this document to separate a pin-to-pin short from a short to ground before replacing the harness or the module. Working the resistance checks in order keeps the repair focused and avoids guesswork on the aftertreatment wiring.
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