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Navigate to DIAGNOSIS screen and monitor diagnostic number D0300 (Grid signal) for the affected axis while manually jogging near the reference position. Verify the grid signal toggles from 0 to 1 within one encoder rotation.

Check encoder cable connections at both motor and amplifier ends. Inspect for bent pins, loose connectors, or cable damage. For serial pulse coders (αi encoders), verify battery voltage on amplifier (should be >3.0V DC).

Power off machine before disconnecting encoder cables to prevent damage to encoder circuitry

Verify Parameter 1815 (reference position return direction) is set correctly: 0=positive direction, 1=negative direction. Incorrect setting causes axis to move away from grid position during final approach.

Check servo amplifier LED status during homing attempt. Red LED or alternating red/green indicates encoder communication fault. Review alarm history in DIAGNOSIS screen for concurrent SV0401-SV0449 encoder alarms.

Manually jog the axis slowly in both directions near the reference point area. Listen for binding, check for obstructions, and verify smooth movement through the entire homing zone plus one encoder revolution (typically 5-20mm additional travel).

Use reduced rapid override and be prepared to stop if resistance is encountered

Monitor DIAGNOSIS screen D0020 (servo load meter) during manual jogging near home position. Values consistently above 70% indicate excessive mechanical load. Check way lubrication, ballscrew condition, and bearing wear.

Verify Parameter 1850 (grid shift amount) is set to zero or a small value (typically 0-10). Excessive grid shift values may position the reference point beyond mechanical limits.

Check Parameter 1240 (reference position return speed during grid search). If set too high (>50 mm/min typical), reduce to 20-30 mm/min to allow reliable grid detection on marginal encoders.

Navigate to DIAGNOSIS > DGN and monitor diagnostic D0000-D0007 (digital input signals) to identify the deceleration dog input for the affected axis. Verify signal changes from 0 to 1 when dog is contacted and returns to 0 when axis moves away.

Inspect the physical deceleration dog for proper mounting, position, and length. Dog must be long enough for initial detection but allow axis to move off the dog by at least one encoder rotation (5-20mm depending on encoder resolution).

Verify Parameters 1005 (dog ignore) and 1006 (dog clamp) are properly configured. Bit settings for the affected axis should match machine mechanical configuration. Incorrect bit settings prevent proper dog signal recognition.

Check that hardware limit switches are not simultaneously active with deceleration dog. Monitor DIAGNOSIS signals during manual approach to home position. Parameter 1007 (overtravel ignore) bits must not be masking valid limit switch inputs.

Never disable hardware limit switches unless performing authorized emergency recovery procedures