SPN 558 FMI 2 is a Detroit fault code reference sheet that documents the idle validation switch inputs reversed diagnostic for DD Series engines built to EPA 2007 and later emissions standards. This single-topic page reproduces the factory-style test order Detroit dealers and independent shops follow for the Idle Validation Switch (IVS) wiring, from confirming related codes through to the final repair decision.
Official document details
| Brand | Detroit |
| Model coverage | DD Series (EPA 2007-Current) |
| System / group | Diagnostic Trouble Codes (DTCs) |
| Suspect Parameter Number | 558 |
| Failure Mode Identifier | 2 |
| Emissions revision | all model years |
| Source | Detroit fault code sheet (© 2017, www.TruckFaultCodes.com) |
| Pages | 1 |
| File size | 0.26 MB |
| Format | |
| Language | English |
SPN 558 FMI 2 troubleshooting steps
The sheet lists the ordered checks Detroit publishes for this code, so a technician can rule out network and power-supply faults before condemning a switch, sensor or module. The main steps are:
- Verify the correct wiring of idle validation switch 1 and 2 from the switch to Common Powertrain Controller (CPC) connectors #1 and #2, following the schematic in the sheet.
- If the switch is wired correctly, replace the throttle position sensor.
Applicable truck models
This code applies to Detroit DD Series diesel engines (EPA 2007 to current) and, for the shared driveline codes, to Series 60 (DDEC VI) installations that use the same Common Powertrain Controller and Motor Control Module architecture. Coverage is defined by the engine and control-module configuration rather than the truck badge, so confirm the exact build against the current model line on the Detroit Diesel official website.
Who needs this SPN 558 FMI 2 manual
This 558 FMI 2 manual is written for diesel technicians and DD Series fleet owners who are correcting reversed idle validation switch inputs and want the exact Detroit test order before ordering parts. Following the documented sequence keeps unnecessary sensor and module replacements to a minimum.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download it.
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