John Deere Engines SPN636FMI5 Fault Code: Camshaft Position Circuit Has High Resistance
Also called Camshaft Position Circuit Circuit Has High Resistance, Camshaft Position Circuit has High Resistance
Camshaft Position Circuit Has High Resistance · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 636 FMI 5 means the ECU has detected high resistance or an open circuit in the camshaft position sensor circuit. This is a Warning-level code. The engine keeps running because the ECU falls back on the crankshaft position sensor for engine speed and position, but the camshaft sensor circuit still needs to be diagnosed and repaired.
Medium severity. This is logged as a Warning-level alarm, not a shutdown fault. The ECU compensates by relying on the crankshaft position sensor to keep the engine running, but the loss of the camshaft signal should be diagnosed and repaired soon since it affects engine control redundancy and can lead to further issues if the underlying wiring problem worsens.
What does John Deere Engines error code SPN636FMI5 mean?
SPN 636 FMI 5 is set when the ECU detects high resistance or an open circuit in the wiring or connectors that make up the camshaft position sensor circuit. The camshaft position sensor tells the ECU exactly where the camshaft is in its rotation, which the ECU uses along with crankshaft position data for precise fuel injection timing and cylinder identification.
When this circuit develops high resistance, the electrical signal from the sensor becomes unreliable or is lost entirely. Rather than shutting the engine down, the ECU switches over to using only the crankshaft position sensor to determine engine speed and position, allowing the engine to keep running in a reduced-redundancy mode.
This code shows up when the ignition is on and the engine is stopped, at the point when the ECU runs its periodic diagnostic check, or when a Harness Diagnostic Mode Test is run in Service ADVISOR. It is not something that only appears while the engine is cranking or running.
Common causes of SPN636FMI5
- Bad terminals or connector at the camshaft position sensor
- Bad camshaft position sensor itself
- Bad harness or wiring between the ECU and the camshaft position sensor
- Bad terminals or connector at the ECU
How to troubleshoot John Deere Engines SPN636FMI5: first checks
- Turn the ignition on with the engine stopped and check for the active code, since this is when the ECU's periodic diagnostic check or the Harness Diagnostic Mode Test will flag the fault
- Inspect the connector and terminals at the camshaft position sensor for corrosion, looseness, bent pins, or moisture intrusion
- Inspect the connector and terminals at the ECU end of the circuit for the same kinds of damage or corrosion
- Visually trace and inspect the wiring harness between the ECU and the camshaft position sensor for chafing, pinches, rodent damage, or corrosion at any splices
- Test or replace the camshaft position sensor if the wiring and connectors all check out good
- Run the Harness Diagnostic Mode Test in Service ADVISOR to help pinpoint exactly where the high resistance or open circuit is occurring
How the code clears
No separate clearing step is listed. Once the underlying wiring, connector, or sensor problem is repaired and the circuit resistance is back to normal, the fault should stop being active on the next ECU diagnostic check. There is no mention of a manual reset procedure beyond fixing the root cause.
Frequently asked questions
What does SPN 636 FMI 5 mean on a John Deere engine?
It means the ECU has detected high resistance or an open circuit in the camshaft position sensor circuit. The ECU logs this as a Warning and switches to using the crankshaft position sensor alone for engine speed and position.
Can I keep operating the machine with this code active?
The engine is designed to keep running using the crankshaft position sensor as a backup, but this is a Warning-level code that points to a real wiring or sensor problem. It should be diagnosed and repaired promptly rather than ignored long-term.
Will this code cause the engine to shut down?
No, the alarm level is Warning, not a shutdown fault. The ECU tries to maintain proper operating conditions by relying on the crankshaft position sensor for engine speed and position.
What usually causes high resistance in the camshaft position sensor circuit?
John Deere lists four possible causes: bad terminals or connector at the camshaft position sensor, a bad camshaft position sensor, a bad harness between the ECU and the sensor, or bad terminals or connector at the ECU.
When does the ECU actually detect and display this code?
It is detected when the ignition is on and the engine is stopped, either during the ECU's periodic diagnostic check or during a Harness Diagnostic Mode Test run through Service ADVISOR.
Do I need a scan tool to diagnose SPN 636 FMI 5?
A scan tool running the Harness Diagnostic Mode Test in Service ADVISOR is the recommended way to help isolate whether the high resistance is at the sensor, the harness, or the ECU connector.