John Deere Engines SPN636FMI10 Fault Code: Camshaft Position Signal Rate of Change Abnormal
Also called Cam Position Input Pattern Error, Pump Position Sensor Input Pattern Error
Camshaft Position Signal Rate of Change Abnormal · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 636 FMI 10 means the ECU is seeing an improper or missing pulse pattern on the camshaft position sensor input (on some systems, the pump position sensor input). The engine can hesitate or die when the code sets but will usually restart, though cranking may take longer than normal. If a crank position sensor code sets at the same time, the engine will not restart until one of the two faults is fixed.
High severity. The engine typically keeps running on the crank sensor input alone after this code sets, and it will usually restart. But if a crank position sensor fault sets at the same time, the engine will die and refuse to restart until one of the two codes is repaired. Prolonged cranking is also a common symptom, so this should be diagnosed promptly rather than ignored.
What does John Deere Engines error code SPN636FMI10 mean?
SPN 636 FMI 10 relates to the camshaft position sensor circuit, and on pump-position-sensor equipped systems, the same code can apply to the high pressure fuel pump's position sensor. Both sensors work the same way: an inductive pickup reads notches on a timing wheel, with one extra notch used to identify cylinder number 1. The ECU combines this cam or pump signal with the crankshaft position signal to know precisely where each piston is, which lets it calculate correct injection timing and fuel quantity for the unit injectors.
FMI 10 specifically means the ECU is seeing an abnormal rate of change or improper pattern on that input, essentially missing or irregular pulses rather than a signal that is simply absent or shorted.
When this code sets, the ECU falls back to using only the crankshaft position input to determine piston position. The engine can still run this way, but starting may take longer, and if the crank sensor also has a problem, the engine will die and stay down until one of the two faults is cleared.
Common causes of SPN636FMI10
- Bad terminals or connector at the camshaft position sensor (or pump position sensor)
- Bad camshaft position sensor or bad pump position sensor
- Bad or damaged wiring harness between the ECU and the sensor, including opens or shorts
- Bad terminals or connector at the ECU connector
- Bad ECU, including possible bad ECU software
- Damaged or burred camshaft timing wheel, or burrs/notches on the cam timing wheel
- Loose camshaft timing wheel or loose crankshaft timing wheel
- Timing off between camshaft and crankshaft
- Camshaft and crank sensor harness connectors accidentally swapped during service
- Water intrusion or loose terminals in connectors
- Battery supply voltage issue to the ECU
- Electrical interference affecting the sensor signal
How to troubleshoot John Deere Engines SPN636FMI10: first checks
- Without disconnecting anything first, visually inspect the ECU connector (60-way on some systems) and the camshaft or pump position sensor connector for dirt, corrosion, damage, or terminals that are pushed back or poorly seated
- Check for water intrusion in any connector along the harness between the ECU and the sensor
- Trace the wiring harness between the ECU and the sensor for chafing, pinches, opens, or shorts
- Confirm the camshaft position sensor and crank position sensor harness connectors were not accidentally swapped during prior service work
- Check that the camshaft timing wheel (or crankshaft timing wheel) is tight and not loose, damaged, or burred
- Look for any accompanying crank position sensor fault code, since that combination will keep the engine from restarting until one is fixed
- Verify battery supply voltage to the ECU is within normal range if electrical interference or intermittent faults are suspected
How the code clears
No separate clearing step is listed. Repair the underlying wiring, connector, sensor, timing wheel, or ECU issue, then verify the code does not reset during a cranking and running cycle. If a crank position sensor code was set alongside this one, both must be addressed since the engine won't restart until at least one is resolved.
Frequently asked questions
What does SPN 636 FMI 10 mean on a John Deere engine?
It means the ECU detected an improper or abnormal pattern of pulses on the camshaft position sensor input (or the pump position sensor input on engines with a high pressure fuel pump position sensor). Instead of a clean, evenly spaced set of pulses, the ECU is seeing missing or irregular pulses.
Will my engine still run with this code set?
Usually yes. The engine may hesitate or die the moment the code sets, but it will typically restart. The ECU switches to using only the crankshaft position input to figure out piston position, and prolonged cranking time may be needed to start the engine.
Why won't my engine restart after this code appeared?
If a crankshaft position sensor trouble code sets at the same time as SPN 636 FMI 10, the engine will die and will not restart until at least one of the two codes is repaired. Check for a companion crank sensor code first.
Can swapped wiring connectors cause this code?
Yes. Accidentally swapping the camshaft position sensor harness connector with the crankshaft sensor harness connector during service can trigger this code, sometimes along with a related crankshaft position fault.
What should I check first before replacing the sensor?
Inspect the ECU connector and the camshaft or pump position sensor connector without disconnecting them first. Look for dirty, damaged, or poorly seated terminals, water intrusion, and damaged wiring, since these are common causes before assuming the sensor itself is bad.
Could a timing problem cause SPN 636 FMI 10?
Yes. A loose or damaged camshaft or crankshaft timing wheel, burrs or notches on the cam timing wheel, or timing that is off between the camshaft and crankshaft can all produce this pattern error.
Is this code only related to the camshaft sensor?
Not always. On engines with a high pressure fuel pump position sensor, the same SPN 636 FMI 10 code can apply to that sensor's input pattern instead of the camshaft sensor, since it works on the same notch-and-timing-wheel principle.