KUKA KRC4 Error Code 420

KUKA Robot Major Safety

Model: KRC4 | Code: 420

Applicable Systems
KR CYBERTECH

Symptoms

Local protective stop. A local protective stop has been triggered. Robot motion is stopped but power mayremain on.

Possible Causes

  • Operator protective stop initiated
  • Safety space violation: robot entered protected zone
  • Safety input signal from external safety device
  • Software limit switch in safety configuration triggered

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code 420 as active
  2. Step 2: Verify all electrical connections, wiring harnesses, and connector seating
    All connections secure, no corrosion, loose pins, or damaged wires
  3. Step 3: Check the safety circuit continuity and all safety interlock switches
    Safety circuit complete, all interlocks engaged
  4. Step 4: Inspect the specific safety device referenced in the fault (door switch, light curtain, E-stop)
    Safety device functional, contacts clean and responsive
  5. Step 5: Verify the brake mechanism: check brake pad wear, spring tension, and air gap
    Brake pads within wear limit, spring tension correct, air gap within spec
  6. Step 6: Test the safety function by simulating the fault condition and verifying response
    Safety function responds correctly within specified time
  7. Step 7: Reset the fault after fixing the safety device or circuit: press RESET
    Fault clears and safety system returns to ready state

How to Reset

To reset: 1) Fix the safety device or circuit fault. 2) Clear the fault on the HMI or controller. 3) Press RESET. Caution: Never bypass safety devices.

Frequently Asked Questions

  • Q: What does fault code 420 mean on the KUKA KRC4?

    Fault 420 indicates a safety-related fault. A safety device or circuit has been triggered. Always investigate the root cause before resetting; never bypass safety devices.

  • Q: Can I continue operating the equipment with fault 420 active?

    No. The equipment has detected a fault condition and has taken protective action (typically stopping or derating). Continuing to operate without fixing the root cause may cause further damage. Always investigate and fix the fault before resuming operation.

Related KUKA Fault Codes

Source: KUKA Robot Controller KRC4 Operating Manual, KUKA Roboter GmbH Documentation

Category: Robot