SPN 599 FMI 4 is the Detroit DD Series diagnostic fault-code sheet (SPN 599 / FMI 4) that documents both cruise control switches, SET and RES, shorted to ground. This 2-page PDF, drawn from the Detroit / Detroit Diesel Corporation (DDC) troubleshooting reference (© 2017), gives the workshop the exact measured checks needed to confirm and repair the fault rather than guess at it.
SPN 599 FMI 4 document details
| Brand | Detroit (Detroit Diesel Corporation) |
| Model coverage | DD Series (EPA 2007-Current); Series 60 (DDEC VI, EPA 2007) |
| System / Group | Diagnostic Trouble Codes (DTCs) – SPN 599 / FMI 4 |
| Source | Detroit / DDC diagnostic troubleshooting reference |
| Year / Revision | © 2017 |
| Pages | 2 |
| File size | 0.21 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code definition (SPN 599, FMI 4)
- Cruise control switch status check
- Driver console display readings
- Troubleshooting steps
- RES and SET switch isolation
- Switch replacement decision
Fault definition and diagnosis
With the ignition on and the cruise control switch in the OFF position (engine not started), the technician reads the driver console display for the cruise control switch status. Depending on whether the RES or SET status is shown, the sheet directs unplugging the corresponding switch to see if the displayed status clears, isolating which cruise control switch is shorted to ground before replacement.
Applicable truck models
It applies to Detroit DD Series engines (EPA 2007 to current) and Series 60 (DDEC VI, EPA 2007) vehicles fitted with the SET and RES cruise control switches. For engine specifications and authorised service information, see the official Detroit engine website.
Who needs the SPN 599 FMI 4 manual
Diesel technicians and workshop owners diagnosing this Detroit DTC with DiagnosticLink or ServiceLink use it to follow the manufacturer sequence step by step, and to confirm the SPN 599 / FMI 4 repair before returning the truck to service.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download it.
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