This SPN 84 FMI 6 reference explains the Detroit DD Series VSS anti-tamper detection that compares vehicle speed against the Antilock Brake System (ABS) reading. It is part of the DiagTechPro truck manuals library and preserves the original TruckFaultCodes.com Detroit fault-code library (Copyright 2017).
Official document details
| Brand | Detroit |
|---|---|
| Model coverage | Detroit DD Series (EPA 2007-current) engines; the same fault-code procedure is also filed under the Detroit Series 60 (DDEC VI, EPA 2007) group. |
| System / Group | DD Series (EPA 2007-Current) / DTCs |
| Fault code | SPN 84 / FMI 6 |
| Source | TruckFaultCodes.com Detroit fault-code library (Copyright 2017) |
| Pages | 2 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Anti-tamper fault overview
- Pre-checks: battery, CAN and ABS faults
- Hardwired versus J1939 VSS
- Connector inspection and resistance checks
Diagnostic steps in the SPN 84 FMI 6 document
The technician first clears any battery (SPN 168) or Controller Area Network (SPN 625) faults, then any ABS faults, and confirms whether the CPC has been reprogrammed. The document then splits by whether the VSS is hardwired or transmitted over J1939, inspects the harness connector for bent or corroded pins, and measures resistance across CPC connector #3 pins 13 and 14.
The Vehicle Speed Sensor (VSS) anti-tamper detection via ABS speed comparison condition on Detroit DD Series trucks is read and cleared with DiagnosticLink (formerly DDDL); the SPN and FMI pair identifies the exact circuit and failure mode. Confirm the code is active and capture freeze-frame data before running the pinpoint tests, then clear it and road-test the truck to verify the repair has held.
Applicable truck models and engines
This document applies to Detroit DD Series (EPA 2007-current) engines; the same fault-code procedure is also filed under the Detroit Series 60 (DDEC VI, EPA 2007) group. For factory service data, parts and warranty information, consult Detroit’s official DD engine support.
Who needs the SPN 84 FMI 6 manual
This reference helps DD Series technicians who see a speed-comparison anti-tamper code and need the ordered list of pre-checks before touching wiring.
The complete PDF is available in the DiagTechPro manuals library; a free account is required to download it.
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