KUKA KSS00028 PLC Communication Error – Causes, Troubleshooting & How to Fix

Error Code Overview

• Error Code: KSS00028
• Category: PLC / Communication / Network
• Severity: High
• System: KRC Controller / PLC-based I/O / Safety PLC / Fieldbus/Profinet/EtherCAT devices
• Impact: Robot motion stops; PLC communication lost; connected modules may be affected

Quick Fix for KUKA KSS00028

If KUKA KSS00028 PLC Communication Error appears, take these immediate steps:

1. Stop robot motion immediately.
2. Check PLC communication cables and connectors.
3. Verify the PLC is poweredon and online.
4. Confirm network/IP configuration is correct.
5. Restart the PLC and KRC controller if necessary.

Tip: Temporary communication interruptions may clear after restart, but repeated KSS00028 alarms usually indicate wiring, network, or PLC hardware issues.

What Does KUKA KSS00028 Mean?

KUKA KSS00028 PLC Communication Error occurs when the KRC controller loses communication with the connected PLC or external control system.

Th is communication is required for:

• Robot/PLC handshake signals
• Automatic cycle start/stop commands
• I/O data exchange
• Safety and production coordination

If communication fails, the robot stops operation until the connection is restored.

In simple terms:

The robot can no longer exchange control data with the PLC, so automatic operation is blocked.

Common Symptoms of KUKA KSS00028

When th is fault occurs, operators often notice:

• Robot stops unexpectedly during automatic cycle
• PLC handshake signals fail
• Robot cannot enter AUTO mode
• Communication LEDs flashing red/yellow
• PLC offline warningson HMI

These symptoms indicate unstable or lost PLC communication.

Common Causes of KUKA KSS00028

Communication Cable or Connector Failure

Physical wiring issues are one of the most common causes.

Examples include:

• Damaged Ethernet/Profinet cable
• Loose connectors
• Bent connector pins
• Broken shielding/grounding

PLC or Communication Module Failure

Hardware failure can interrupt data exchange.

Possible faults include:

• PLC CPU offline
• Communication card malfunction
• Overheated PLC module
• Failed interface board

Incorrect Network Configuration

Communication settings must match exactly.

Typical configuration issues:

• Incorrect IP address
• Duplicate IPon network
• Wrong subnet settings
• Device name mismatch

Fieldbus Timeout or Watchdog Expiry

Communication delays may trigger timeout protection.

Common reasons:

• Network overload
• Unstable industrial switch
• Delayed PLC response
• Packet losson network

Electrical Noise or Grounding Issues

Industrial EMI can affect communication reliability.

Potential causes:

• Poor cable shielding
• Improper grounding
• High-voltage equipment interference
• Power noiseon communication line

Main Causes of KUKA KSS00028

1. Communication Cable Failure

Damaged or loose cables may interrupt signal transmission:

• Broken Ethernet/Profinet cable
• Bent connector pins
• Loose terminal connections

This is one of the most common causes.

2. PLC or Interface Module Failure

Faulty hardware may prevent communication:

• PLC CPU fault
• Communication module overheating
• CP1616 card malfunction

3. Incorrect Network Configuration

Configuration mismatches may include:

• Wrong IP address/subnet
• Duplicate network address
• Incorrect device name assignment
• PLC mapping inconsistency

4. Fieldbus Timeout / Watchdog Expiry

If communication response exceeds allowed timing:

• Watchdog timer expires
• PLC handshake is lost
• Robot stops for safety

Often caused by network overload or unstable switches.

5. Electrical Noise / Grounding Problems

Industrial EMI interference can disrupt communication:

• Poor shielding
• Ground loops
• High-current equipment nearby

How to Troubleshoot KUKA KSS00028

Step 1 – Check PLC Status

Inspect PLC panel and confirm:

• CPU is online
• No fault LEDs present
• Communication module active

Step 2 – Inspect Communication Wiring

Check:

• Cable integrity
• Connector seating
• Bent/damaged pins
• Shield grounding condition

Step 3 – Verify Network Configuration

Confirm:

• IP addresses match project settings
• Device names are assigned correctly
• Subnet configuration is valid

Step 4 – Test Communication Interface Hardware

Inspect:

• CP1616/fieldbus card
• Internal communication board
• Expansion modules

Replace faulty hardware if required.

Step 5 – Monitor Watchdog / Timeout Logs

Review diagnostics for:

• Communication timeout events
• Packet loss
• Network interruption history

Step 6 – Reset and Retest

After repair:

1. Clear KSS00028 in SmartHMI
2. Restart PLC and KRC controller
3. Test AUTO mode
4. Monitor communication stability

Recommended Components to Check

How to Troubleshoot KUKA KSS00028

Step 1 – Check PLC Status

Confirm the PLC:

• Is poweredon
• Shows no fault LEDs Is online and running normally

Step 2 – Inspect Communication Wiring

Check all network/PLC cables for:

• Damage
• Loose connections
• Bent pins
• Shielding integrity

Step 3 – Verify Network Configuration

Confirm:

• IP addresses match configuration
• Device names are correct
• Subnet settings are valid
• No duplicate network addresses exist

Step 4 – Inspect Communication Hardware

Review status of:

• PLC communication modules
• Robot fieldbus/communication card
• Internal controller interface boards

Replace faulty hardware if needed.

Step 5 – Check for Timeout or Packet Loss

Review diagnostics/logs for:

• Communication timeout events
• Packet drops
• Watchdog alarms
• Intermittent disconnects

Step 6 – Restart and Retest

After corrections:

1. Clear KSS00028 in SmartHMI
2. Restart PLC and KRC controller
3. Test AUTO/EXT mode
4. Monitor communication stability

Pro Diagnostic Tip

If KSS00028 happens intermittently instead of constantly:

The issue is often network stability related, not complete hardware failure.

Common intermittent causes include:

• EMI interference
• Loose connectors
• Switch overload
• Brief PLC reboot/reset

Intermittent communication faults are usually harder to diagnose than complete failures.

How to Fix KUKA KSS00028

Dependingon the cause, repair may include:

• Replacing damaged communication cables
• Repairing/replacing faulty PLC hardware
• Reconfiguring network/IP settings
• Replacing failed communication modules
• Improving grounding/shielding

How to Prevent KUKA KSS00028

To reduce future PLC communication alarms:

• Inspect cables regularly
• Secure all connectors properly
• Maintain stable grounding/shielding
• Keep PLC/network firmware updated
• Avoid routing communication cables near power cables

Related KUKA Communication & Safety Errors

• KUKA KSS00021 Bus Communication Error– Indicates issues with the bus communication, preventing data exchange between devices or subsystems.
• KUKA KSS00022 Fieldbus Communication Error– Occurs when there is a failure in the fieldbus network communication, impacting system integration and data transfer.
• KUKA KSS00023 Profinet Communication Error– Triggered by a breakdown in Profinet communication, affecting data exchange between the robot and connected devices.
• KUKA KSS00024 EtherCAT Communication Error– Occurs when EtherCAT communication fails, disrupting communication between the robot and external devices or controllers.
• KUKA KSS00025 Device Communication Error– A general communication failure between the robot and an external device, possibly due to incorrect wiring, misconfiguration, or component failure.

These alarms often relate to PLC communication, safety integration, and control network stability.

FAQ

Can the robot operate with KUKA KSS00028?

No. Automatic operation is blocked until PLC communication is restored.

Why does KUKA KSS00028 happen?

Common causes include:

• Damaged communication cables
• PLC hardware failure
• Incorrect network configuration
• Fieldbus timeout
• Electrical interference

How do I fix KUKA KSS00028 quickly?

1. Check PLC status
2. Inspect communication cables
3. Verify network/IP settings
4. Restart PLC and robot controller

Can unstable network switches cause KSS00028?

Yes. Packet loss or unstable industrial switches can trigger communication timeout alarms.