Fanuc alarm SP9048: POSITION CODER 1-ROT SIGNAL ABNORMAL

What it means

The one-revolution signal of the position coder was received but is abnormal relative to the A/B-phase channels: it arrived at an implausible phase relationship or with distorted width. This differs from outright loss of the signal and usually points at marginal signal quality rather than a dead sensor.

Likely causes

• Weak or dirty one-rotation mark causing marginal threshold detection
• Incorrect pulses-per-revolution parameter for the fitted coder
• Deteriorating coder electronics producing inconsistent mark timing

Replacement parts

We supply the following units for this alarm — tested, warranty-backed:

• A860-0360-B101

  Position coder (spindle encoder) · Common cause

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