This SPN 3597 FMI 3 document is a Detroit DD Series fault-code procedure for the high side digital output 1 circuit failed high condition on GHG14 engines. It follows the voltage checks made at the Diesel Exhaust Fluid dosing unit harness.
Official document details
| Brand | Detroit |
| Model coverage | Detroit DD Series (EPA 2007-Current) |
| System / group | DD Series / DTCs |
| SPN | 3597 |
| FMI | 3 |
| Condition | high side digital output 1 circuit failed high |
| Emissions level | GHG14 |
| Source | Detroit Power Service Literature |
| Pages | 2 |
| File size | 0.3 MB |
| Format | |
| Language | English |
SPN 3597 FMI 3 troubleshooting steps
The routine begins by disconnecting the Diesel Exhaust Fluid dosing unit harness connector and inspecting it for bent, spread or corroded pins. With the ignition on you measure voltage between pins 4 and 7, then between pin 4 and engine ground, to separate a short to battery voltage at the ACM2.1 connector from an open supply wire back to pin 22 of the aftertreatment module.
- Fault description: high side digital output 1 circuit failed high
- Steps 1 to 2 – Disconnect DEF dosing unit and inspect pins
- Step 3 – Ignition on (key ON, engine OFF)
- Step 4 – Voltage between pins 4 and 7
- Step 5 – Voltage between pin 4 and engine ground
Applicable truck models
This fault code applies to Detroit DD Series GHG14 diesel engines that use a Diesel Exhaust Fluid dosing unit fed from the ACM2.1 aftertreatment module. Confirm the connector pinout against Detroit Power Service Literature on the official Detroit Diesel website.
Who needs this SPN 3597 FMI 3 manual
Diesel technicians and workshop owners diagnosing a DEF dosing supply fault on a GHG14 Detroit engine use this document to locate a short to battery voltage or an open feed before replacing the dosing unit. The two-measurement flow keeps the job efficient and prevents a good dosing unit from being condemned when the real fault is in the harness.
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