SPN 636 FMI 2 is the Detroit DD Series diagnostic trouble code for No match of camshaft and crankshaft signals, documented in this 2-page PDF from the DD Series (EPA 2007-Current) DTC library. The reference gives the fault description, enabling conditions and the full step-by-step troubleshooting flow a technician follows. It is sourced from the TruckFaultCodes.com Detroit fault code library (© 2017).
Official document details
| Brand | Detroit |
| Model coverage | DD Series (EPA 2007-Current) |
| System / Group | DTCs — SPN 636, FMI 2 |
| Fault | No match of camshaft and crankshaft signals |
| Year / Revision | All years |
| Pages | 2 |
What SPN 636 FMI 2 means
This diagnostic trouble code sets when the Motor Control Module finds no match of the camshaft and crankshaft signals on the DD Series engine. The monitored parameters are the Camshaft (CMP) and Crankshaft (CKP) sensors, and the fault commonly triggers the MIL and CEL dash lamps.
How to diagnose SPN 636 FMI 2
The document sequences the camshaft-to-crankshaft correlation check:
- Confirm no other camshaft (SPN 723) or crankshaft (SPN 636) circuit faults are active; repair those first.
- If the engine was recently overhauled, verify camshaft timing and gear lash per Power Service Literature.
- Remove and inspect the Camshaft Position (CMP) sensor for physical damage.
- Replace the CMP sensor and re-verify the signal correlation as directed.
On the DD Series, the Motor Control Module compares the camshaft and crankshaft sensor signals to establish engine phase for fuel timing. When the two signals do not correlate, a timing or sensor problem is indicated, so recent valve-train work must be ruled out before condemning a component.
Who needs this fault code
Engine rebuilders use this sheet after valve-train work to confirm camshaft timing before condemning a sensor. It ties the no-match condition to the correct verification steps for the Detroit DD Series. For the underlying system design, cross-reference the official Detroit Diesel service portal.
The full PDF is available in the DiagTechPro manuals library, free account required to download.
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