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SPN 636 FMI 10

Engine Position Sensor (Camshaft) — Abnormal rate of change.
The value is changing faster than is physically believable.

What the SPN covers: Camshaft position signal used for injection timing and cylinder identification. More on SPN 636.

What FMI 10 usually points to: Intermittent wiring, a sensor glitch, or a sudden real event such as a burst hose. More on FMI 10.

Severity

HIGH — limit use, diagnose now

May cause hard starting, rough running or no-start.

Likely causes

  1. Faulty cam sensor
  2. Wrong air gap or debris on the sensor
  3. Damaged tone ring
  4. Wiring fault

Checks & fixes (easiest first)

  1. Inspect the sensor tip for metal debris
  2. Check resistance and wiring
  3. Compare cam and crank signals with a scope
  4. Check for SPN 637 together

FAQ

What does SPN 636 FMI 10 mean?

Engine Position Sensor (Camshaft) — abnormal rate of change. The value is changing faster than is physically believable.

Is SPN 636 FMI 10 serious?

May cause hard starting, rough running or no-start.

What should I check first for SPN 636 FMI 10?

Inspect the sensor tip for metal debris; Check resistance and wiring; Compare cam and crank signals with a scope.