Troubleshooting KUKA KRC2 Errors 432, 250, 216: KSD/KPS Faults

Overview

The error cluster 432 "Check of maximum current for KSD 1 not possible", 250 "Incorrect servo parameter KPS 1", and 216 "Drive error pm1 No 3001" is a recognized KRC2 (KUKA Robot Controller, second generation) fault pattern reported on cabinets running KSS 5.2 through KSS 5.6. The three messages together indicate that the KPS (KUKA Power Supply) cannot complete a clean parameter and current-limit handshake with the KSD chain (KUKA Servo Drive), and that KSD 1 has returned an internal fault code 3001 to the controller through power module 1. When all three errors appear simultaneously on every KSD in the cabinet, the root cause is almost always upstream on the shared KPS-to-first-KSD data bus rather than on the individual drives. Field experience on robots that have just been transported or recommissioned places an unseated or partially inserted RJ45 data cable as the leading cause.

Affected Systems and Configurations

The KRC2 documentation set is published through the KUKA customer portal at KUKA documentation downloads. The specific KSS 5.x operator manual (KUKA System Software 5.5 Operating and Programming Instructions) and the KR C2 KR C2 LR Assembly Instructions manuals are the canonical references for cabinet layout, KPS/KSD part numbers, and connector pinouts.

Error Code Reference

Error 432 — "Check of maximum current for KSD 1 not possible"

During the KPS startup self-test the KPS polls every KSD in the chain for its configured Imax (maximum drive current) parameter. If KSD 1 does not respond within the poll window, returns a corrupt parameter block, or the response is dropped at the physical layer, the controller aborts the check and logs 432 against KSD 1. The same message repeats against KSD 2..7 when the underlying bus is down, because the KPS cannot reach any KSD and the controller defaults to reporting the first KSD it cannot validate.

Error 250 — "Incorrect servo parameter KPS 1"

The KPS stores a parameter set describing the bus voltage, current limit, and module identifier. The KRC2 (via the DSE card or KPC) cross-checks the live KPS parameters against the as-built configuration. A mismatch is logged as 250. The message fires after a KPS replacement if the parameter file on the KPC was not reloaded, after a project edit, or when the communication channel that carries the parameter block is degraded enough to corrupt the response.

Error 216 — "Drive error pm1 No 3001"

Error 216 is the controller-level wrapper for a KSD-side fault. The token pm1 points to power module 1, and No 3001 is the KSD-internal fault number. On KSD generation 1.x (KSD 1.0, 1.1, 1.2) the internal code 3001 corresponds to a current-monitor / IGBT desaturation / encoder-power event logged by the drive's own diagnostics. When the KSD cannot return the fault to the KPS over the data bus, the KPS surfaces it as 216/3001 instead of suppressing it.

Root Cause Analysis

A first-time fault on all 6 or 7 KSDs simultaneously is almost never an independent hardware failure on every drive. The common bus is the KPS-to-first-KSD data cable, and the most frequent field causes in priority order are:

1. RJ45 data cable between the KPS and KSD 1 not seated, partially crimped, or vibrated loose during transport. This was the confirmed root cause in the source case.
2. SERCOS fiber ring misrouted, missing a connector, or a TX/RX swap on one KSD.
3. KPS internal failure where the DC link droops below threshold during the parameter upload, causing intermittent KPS responses.
4. Mixed KSD hardware revisions after a maintenance swap, with the KPS firmware not supporting the newer revision.
5. Defective DSE or KPC communication card after an ESD event or improper shutdown.

KPS and KSD Architecture

The KPS is a single 3-phase input converter that rectifies the mains and regulates the common DC bus for every KSD. The KSD modules are 1-axis servo amplifiers that draw from that DC bus and drive the individual axis motors.

The data cable between the KPS and KSD 1 carries the KUKA internal drive service bus, sometimes called the DSE bus. The chain is daisy-chained from KSD 1 to KSD 2, 3, and so on. Every KSD therefore has two RJ45 / XRJ ports — one to the upstream device, one to the downstream — and a single broken or swapped link on the chain takes down every KSD downstream of the break.

Diagnostic Procedure

Follow this sequence before swapping any module. Skipping a step is the most common cause of misdiagnosis.

Step 1 — Capture the Logbook

1. From the KCP (KUKA smartPAD), navigate to Diagnosis > Logbook.
2. Filter by category Drive and Power supply.
3. Note the chronological order of 216, 250, 432, and any preceding warnings.
4. Export the log via the smartPAD USB port to a FAT32 stick for record-keeping and warranty reference.

Step 2 — Verify the 24 VDC Auxiliary Supplies

Measure at the KPS terminal block and at the KSD X3 connector:

Undervoltage on the KSD logic rail is a common cause of 432 because the KSD cannot complete its parameter upload to the KPS.

Step 3 — Inspect the KPS-to-KSD Data Cabling

1. Open the main disconnect and wait a minimum of 5 minutes for the DC link to discharge below 50 VDC. Verify with a CAT-III DMM on the KPS DC-link test points.
2. Open the cabinet and identify the KPS module — large black heatsink, 3-phase input, 600 to 700 VDC bus bars going to the KSD stack.
3. Trace the data cable loom from the KPS to the first KSD, then daisy-chain to KSD 2 through 7.
4. Reseat every RJ45 / XRJ connector until the latch clicks audibly.
5. Inspect each connector for bent pins, oxidation, contamination, or broken latches. Replace any connector with visible damage.
6. For SERCOS fiber variants, verify that TX on one device connects to RX on the next, that no fiber is pinched, and that connectors are clean. A single 90° bend with a 25 mm radius breaks the optical link.

Step 4 — Check KPS Parameter File

1. On the KPC, open the project in KukaConfig for KSS 5.x or WorkVisual for KSS 8.x.
2. Confirm the KPS catalog entry matches the installed module (KPS 600 / KPS 900 / KPS 1200) and the firmware revision on the sticker.
3. If the KPS has been replaced or the project edited, reload the parameter set to the KPS via the DSE service tool.

Step 5 — Cold-Start and Re-Observe

After reseating the data cables, perform a cold start from the main disconnect (not a warm restart). Monitor the KPS LED sequence: green "ready" within 10 seconds, no red fault LED. From the KCP run Diagnosis > Drive status and confirm every KSD reports OK and bus voltage within ± 5 % of the set point.

KSD Swap Diagnostic

If error 432 persists only on KSD 1 after the cabling and parameters are verified, perform a hardware swap test to localize the fault to the KSD or the KPS output channel.

1. Cold-start the controller to clear the logbook.
2. Confirm 432 still reports against KSD 1 with all KSDs seated.
3. Power down and swap KSD 1 with KSD 2. Both modules must be the same hardware revision (1.0/1.1/1.2) for the test to be valid.
4. Power up. If the error follows the swapped drive to the new axis position, the KSD is faulty. Replace it.
5. If the error stays on the original KSD 1 slot, the KPS output channel or the backplane is at fault. Escalate to KPS-level diagnosis.

KPS Isolation Test

1. Disconnect the KPS mains supply and verify zero energy state on the DC link.
2. Measure the resistance of the KPS-to-KSD data pair to chassis ground. A reading below 1 MΩ indicates a damaged cable or a KSD input short.
3. Power the cabinet with the KPS data bus disconnected at the KPS output. If the 432 message still appears at the KPS only, the KPS itself is the source.
4. If available, substitute a known-good KPS from a spare cabinet. Re-upload the parameter set before powering the KSDs.

Logbook Pattern Interpretation

Verification After Repair

1. Cold-start the controller from the main disconnect.
2. Confirm the KPS LED sequence: green "ready" within 10 seconds, no red fault LED.
3. From the KCP, run Diagnosis > Drive status — every KSD should show OK and the measured bus voltage within ± 5 % of the set point.
4. Jog each axis in T1 mode at 5 % override and verify the current draw on each KSD is below the configured Imax.
5. Run a 10-minute reference program with all axes moving through their full travel.
6. Re-check the logbook for any new 4xx or 2xx messages.

Preventive Measures

1. After every cabinet move, perform the data-cable reseat procedure as a documented commissioning step.
2. Label every RJ45 cable in the KPS-to-KSD chain with Kuka-spec markers so vibration does not move them out of order.
3. Document the KPS firmware version and the KSD revision on the cabinet door "as-built" card.
4. Replace the KPS cooling fans at the 40 000 h interval; fan failure leads to KPS overtemperature and parameter corruption.
5. Add UPS-backed 24 VDC to the KSD logic supply to prevent parameter loss on short mains interruptions.
6. Keep a known-good spare KPS and one spare KSD of each installed revision in the spare parts cabinet, pre-loaded with the correct parameters.

Related Fault Patterns