What is error-diagnosis?

A troubleshooting guide for programmable logic controller systems, which control industrial machinery. It explains how to investigate PLC, drive, EtherCAT, CODESYS, and CiA 402 error codes and motion faults.

Use it to decode raw fault codes, diagnose drive and EtherCAT problems, investigate CODESYS failures, and find recovery procedures in related manuals.

It reduces the risk of guessing what an error code means, since the same code can have different meanings across vendors and communication standards.

How efranceschetti/festo-codesys-mcp configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to efranceschetti/festo-codesys-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/efranceschetti/festo-codesys-mcp/main/.claude/skills/error-diagnosis/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/efranceschetti/festo-codesys-mcp

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/efranceschetti/festo-codesys-mcp/error-diagnosis/github.svg)](https://agentmods.dev/skills/efranceschetti/festo-codesys-mcp/error-diagnosis)

Your own site

<a href="https://agentmods.dev/skills/efranceschetti/festo-codesys-mcp/error-diagnosis"><img src="https://agentmods.dev/badge/skills/efranceschetti/festo-codesys-mcp/error-diagnosis/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/efranceschetti/festo-codesys-mcp/error-diagnosis"><img src="https://agentmods.dev/badge/skills/efranceschetti/festo-codesys-mcp/error-diagnosis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 87 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 639 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00087	$0.00639
Opus 5	$0.00044	$0.00319
Sonnet 5	$0.00017	$0.00128
Haiku 4.5	$0.00009	$0.00064

Measured 9d ago against content hash c54aea56983c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

error-diagnosis scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/error-diagnosis/SKILL.md · 29 lines

How it starts

The opening of the file, as written. The whole thing — 29 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Error Diagnosis

Never interpret an error code from memory — codes overlap between vendors and profiles.

1. Decode

plc_lookup action=error_code with the raw code (accepts 0x…, 16#…, decimal) — instant database hit.
Not found -> explain_error_code (deep search across all topics + all 19 manuals).

2. Contextualize

Drive/motion fault -> plc_knowledge action=topic festo-ptp (library error list) or action=read_manual hw-cmmt-servo (recovery procedures, FAQ).
EtherCAT comms -> topic ethercat-cia402 (AL status, ESM transitions).
Anything else -> plc_knowledge action=search with the code AND with symptom words.

3. CODESYS crashes — is it even a code fault?

Two IDE/runtime failure modes are NOT bugs in the ST — do not chase them as error codes. Full runbook: plc_knowledge action=topic codesys-gotchas.

Cosmetic plugin crash (Festo CPX-E). A red popup Exception while changing device editor visibility / Fatal error: cannot load module: CPX_E_System / Object reference not set to an instance of an object in DeviceEditor.OnVisibilityChanged fires when you click the Device or a Festo CPX-E node in the device tree. It does NOT block Build, Download, Run, Watch, or Force — click OK and continue; avoid opening those device tabs. Reinstalling the plugin, changing the CODESYS version, or recreating the project does NOT fix it (compiled vendor DLL bug — wait for a vendor update or ignore).
Chronic runtime crash. Use the triage in codesys-gotchas: probe ports (base-firmware port alive while the runtime ports die = runtime process exception, not power/network); read the device Log (Not matching retain area cleared = persistents wiped); pull the core dump (external abort at erratic addresses = hardware/electrical or compiler↔runtime ABI mismatch, NOT IEC logic — a logic bug logs an IEC exception instead).

4. If truly not found locally

Say so explicitly, then search the web — and suggest saving the finding as a .md in knowledge/manuals/ so it is local next time.

Read the full file on GitHub · 29 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

9d ago First seen · 29 lines · 87 tokens per session scan A c54aea56983c

Subscribe to this mod's changes

error-diagnosis is a skill published in the GitHub repository efranceschetti/festo-codesys-mcp (1 stars, last pushed 4d ago), licensed MIT. It adds 87 tokens to every session and 639 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Debugging Hardware and IoT automation codesys cpx ethercat festo iec-61131-3

festo-codesys-mcp: Skill for Claude Code

Borrowing it

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

Error Diagnosis

1. Decode

2. Contextualize

3. CODESYS crashes — is it even a code fault?

4. If truly not found locally

What this file has done since we first saw it

Other skills, from other repositories

codesys

eide

workflow

diagnose-hid-keycodes

8051-mcu-debug

cortex-m-debug