John Deere Engines SPN637FMI7 Fault Code: Crankshaft Position and Camshaft Position Signals Out of Sync
Also called Crank Position/Cam Position Out of Sync, Crank Position/Pump Position Timing Moderately Out of Sync, Crankshaft Position/Pump Position Timing Moderately Out of Sync, Crankshaft and Camshaft Position Signals Out of Sync
Crankshaft Position and Camshaft Position Signals Out of Sync · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 637 FMI 7 means the ECU sees the camshaft or fuel pump position signal out of sync with the crankshaft position signal. The engine may die and not restart, or it may keep running with low power. This is a warning-level code but it directly affects starting and running ability, so treat it as urgent.
High severity. The engine may die and fail to restart, or keep running with reduced power. One version notes engine protection is enabled and prolonged cranking may be required to start. It is not immediately catastrophic to the engine like an overheat code, but it can strand the machine, so it should be diagnosed promptly rather than run through a shift.
What does John Deere Engines error code SPN637FMI7 mean?
The crank position sensor and the cam position sensor (or, on some engines, the fuel pump position sensor) are both inductive pickups that read notches on timing wheels or gears. The ECU uses the crank signal to know engine speed and exact piston position relative to top dead center. It uses the cam or pump signal to know when a cylinder has finished its compression stroke.
Because there is a known, fixed relationship between these two signals, the ECU can tell when they fall out of sync with each other. When that happens it sets SPN 637 FMI 7, meaning the two signals are not lining up the way they should during normal operation.
This matters because injection timing and fuel quantity calculations depend on both signals agreeing. If they disagree, the ECU cannot reliably calculate start of injection, which can cause the engine to die, refuse to restart, or run with low power.
Common causes of SPN637FMI7
- Crankshaft or camshaft out of time, or timing off between camshaft and crankshaft
- Bad terminals or connectors at the camshaft position sensor, crankshaft position sensor, pump position sensor, or ECU
- Open or short in the wiring harness between the sensors and the ECU
- Bad crankshaft timing wheel, bad camshaft timing gear, or burrs/notches on the timing wheels
- Loose camshaft position sensor or loose upper idler gear timing (pump position timing issue)
- Bad camshaft position sensor, crankshaft position sensor, or pump position sensor itself
- Bad ECU or bad ECU software
- Water or contamination in connectors causing an intermittent signal issue
How to troubleshoot John Deere Engines SPN637FMI7: first checks
- Visually inspect the 60-way ECU connector along with the crank position sensor and cam or pump position sensor connectors for dirty, damaged, or poorly seated terminals
- Check the wiring harness between the sensors and the ECU for chafing, open circuits, or shorts, and look closely for water intrusion in any connector
- Confirm camshaft and crankshaft timing are correct, and inspect the timing wheels and gears for burrs, notches, or looseness (including the upper idler gear on pump position setups)
- If the engine died and will not restart, note that disconnecting the crank position sensor has, in some cases, allowed the engine to start again, which points to a sensor or signal problem rather than a mechanical timing fault
- Check for other related codes in the troubleshooting sequence, such as SPN 636 or SPN 637 with FMI 8, FMI 10, or FMI 2, since these are meant to be diagnosed before chasing FMI 7
How the code clears
No separate clearing step is listed. Repair the underlying wiring, sensor, timing, or ECU issue found during diagnosis, then verify the code does not reset during normal operation. One version notes the code is displayed when the engine is running above 400 rpm with the error condition active, so a successful test drive or run-up above that speed without the fault returning is a reasonable way to confirm the repair.
Frequently asked questions
What does John Deere SPN 637 FMI 7 mean?
It means the engine control unit detected that the camshaft position signal, or on some engines the fuel pump position signal, is out of sync with the crankshaft position signal. These two signals are supposed to have a fixed relationship, and when they do not match up, the ECU sets this code.
Can I keep driving or operating with this code active?
It is risky. The engine may die and possibly not restart, or it may continue running but with low power. Since one version also notes that engine protection is enabled, it is best to get the machine diagnosed rather than continue working.
Why did my engine die and won't restart with this code?
This can happen when the cam, crank, or pump position signal is bad enough that the ECU cannot calculate injection timing. In some cases, disconnecting the crank position sensor has allowed the engine to start again, which points toward a sensor or wiring issue rather than a mechanical timing problem, but this should be confirmed by a technician.
What causes the cam and crank signals to go out of sync?
Causes include the crankshaft or camshaft being physically out of time, damaged or burred timing wheels or gears, bad or corroded connectors at the sensors or ECU, an open or short in the harness, a failed sensor, or a bad ECU. On pump position setups, loose upper idler gear timing can also cause it.
Is this the same as a crank/cam correlation code on other engines?
Yes, conceptually. Different John Deere engine variants describe this same SPN 637 FMI 7 fault using either a camshaft position sensor or a fuel pump position sensor, but the underlying issue is the same: the secondary timing signal disagrees with the crankshaft signal.
Why does the engine take a long time to crank before starting?
One version of this fault notes that prolonged cranking time may be required to start the engine while this warning is active, which is a control unit response tied to the sync issue between the pump position and crank sensor signals.
What should a mechanic check first?
Start with a visual inspection of the ECU connector and the crank and cam or pump position sensor connectors for dirty, damaged, or poorly seated terminals, then check the wiring harness for damage and confirm camshaft-to-crankshaft timing is correct.