DIAGIA
DIAGIA is an AI fault-diagnosis assistant for French car workshops. Technicians enter OBD2 trouble codes and symptoms, then receive ranked probable causes, test procedures and a PDF report in under 30 seconds. Access requires a verified SIRET number.
What is DIAGIA?
DIAGIA is a diagnostic assistant for car repair shops, published by the Paris company KORONTIC SYSTEMS and sold only to automotive professionals trading in France. The working loop is deliberately narrow. A technician plugs in whatever OBD2 scan tool the workshop already owns, notes the fault codes, describes the symptoms in the app, and gets back a ranked list of probable causes together with the tests to run and a suggested repair method. The vendor advertises a reply in under 30 seconds.
Three things carry the product. The first is the reasoning layer, which treats fault codes in the context of the whole vehicle and the reported behaviour instead of translating each code one by one. The second is a proprietary knowledge base organised by engine type and vehicle family, described as continuously updated and covering all light vehicles, passenger and commercial, across the mainstream European and Japanese marques. Technically the publisher describes a retrieval-augmented setup: confidential language models, vector embeddings, and its own retrieval system over that automotive corpus. The AI supplier itself is not named. The third is fitness for the shop floor — an interface meant to be used with gloves on, hands-free voice dictation, an optional camera OCR scan, and no proprietary hardware to buy.
A registration-plate lookup pre-fills make, model, engine and VIN through a third-party service drawing on the French vehicle registration system, with the result cached in an EU database. On the Pro and Expert plans the session ends in a PDF report that the garage can hand or email to the car's owner, and a hotline ticket can push a stubborn case to a human expert technician for a reasoned answer within one working day.
The framing is consistently that of a decision aid. Both the terms and the legal notice warn that the models can hallucinate, that every suggestion must be verified before any work is carried out, and that the technician alone remains responsible for the repair. Access is tightly gated: a verified SIRET number, one of four accepted activity codes, and a minimum age of 18. The service runs on iOS and Android, with a web portal reserved for subscription and billing.
What it does
- Reads OBD2 trouble codes alongside the reported symptoms and correlates them rather than treating each code in isolation
- Returns the probable causes ranked by likelihood, with the tests to run and the intervention method
- Generates a PDF diagnostic report that can be sent to the vehicle owner (Pro and Expert plans)
- Pre-fills the vehicle record from the registration plate, retrieving make, model, engine and VIN
- Accepts the question hands-free by voice dictation, for use with gloves on
- Escalates a complex case to a human expert technician through hotline tickets (Pro and Expert plans)
- Keeps a full searchable history of diagnoses, with workshop statistics on the higher plans
When to use DIAGIA / When not to
A quick filter to help you decide if DIAGIA is the right fit.
When to use DIAGIA
- Technicians in independent garages wrestling with intermittent or electronic faults that resist the usual process of elimination
- Service advisors who have to explain a repair to the car owner and back the quote with a written diagnostic report
- Workshop foremen running several technicians, who need shared access and a monthly activity report across the team
- Multi-brand and body-shop technicians working without access to manufacturer-specific diagnostic tooling
- Parts advisors and parts managers under pressure to stop ordering components on a hunch
When not to use DIAGIA
- Car owners and DIY mechanics: signing up requires an active French SIRET number, which is checked at registration
- Automotive professionals based outside France, since the terms restrict the service to businesses trading in France
- Workshops whose registered activity code falls outside the four accepted ones (4520A, 4520B, 4519Z, 4520C)
- Very low-volume garages, for whom a firm twelve-month commitment plus a €499 activation fee is hard to justify
- Software teams hoping to embed the diagnosis in their own system: there is no public API and no third-party integration
How to use DIAGIA
A typical end-to-end flow, from setup to results.
- Check eligibility first: the service is open only to automotive businesses trading in France, with an active SIRET number, one of four accepted activity codes and an operator aged at least 18
- Create an account on the website through a four-step form covering personal details, company identity, business address and password
- Enter the SIRET number and pick the activity code from the four allowed; the number is verified during signup
- Choose a plan — Starter, Pro or Expert — and a billing period, monthly or annual
- Register a payment card: an authorisation for zero is taken, with no charge during the 14-day trial
- Install the DIAGIA app from the App Store or Google Play
- On the vehicle, connect any OBD2-compatible scan tool and read off the fault codes
- Enter the registration plate to pre-fill the vehicle record, or type in make, model and engine manually
- Describe the fault and the symptoms, by keyboard or by voice, and read back the ranked causes, tests and method
- Generate the PDF report for the customer, or open a hotline ticket if the case resists — and cancel before day 14 if you do not want to be charged
Pros & Cons
Pros
- Works with any OBD2 scan tool the workshop already owns — no proprietary hardware, no installation, no calibration
- Legal and technical documentation well above what a company this young usually publishes: dated privacy policy, full terms, legal notice and a named list of eleven subprocessors
- Data hosting is committed to the European Union, and the cached registration-plate lookups are explicitly kept there too
- The whole price list is published, activation fee included, with nothing hidden behind a sales call
- The risk of hallucination is stated plainly in both the terms and the legal notice, rather than buried or ignored
- A human fallback is contractual, not decorative: hotline tickets reach an expert technician with a promised turnaround
- The PDF report gives the garage something written to justify the work to a sceptical customer
Cons
- A firm twelve-month commitment with no early exit: ask to leave and the remaining monthly instalments still fall due
- The subscription renews tacitly for another twelve months unless you give notice before the anniversary date
- Notice is only valid by email with acknowledgement of receipt or by registered letter — a support ticket, an in-app message or a phone call does not count
- A one-off €499 activation fee excl. VAT lands on top of the first payment, and the 14-day trial requires a card and converts automatically
- The entry plan allows only four diagnoses a month for €99.90 excl. VAT, and there is no permanent free tier
- No public API and no third-party integrations, so the diagnosis cannot be fed into an existing workshop system
- The headline performance figures are the vendor's own, with no published method; the homepage's own "diagnoses performed" counter shows nothing but a dash
Pricing & Plans
There is no permanent free plan. A 14-day free trial covering up to four diagnoses is offered, but it requires a payment card registered up front and converts automatically into a paid subscription unless cancelled before the fourteenth day. The cheapest paid entry point is the Starter plan at €99.90 per month excluding VAT. A one-off activation fee of €499 excluding VAT is payable once per company on top of the subscription, and 20% VAT applies to every amount shown. All plans are subscribed for a firm twelve-month term, so the minimum first-year outlay at the entry level comes to €1,697.80 excluding VAT.
- 4 diagnoses per month
- advanced diagnostic AI
- full history
- iOS and Android apps
- no hotline tickets and no advanced statistics
- 30 diagnoses per month
- everything in Starter plus 2 hotline tickets per month
- advanced statistics
- PDF reports and priority support
- presented as the most popular plan
- 60 diagnoses per month
- everything in Pro plus 5 hotline tickets per month
- multi-user access
- a monthly activity report and dedicated support
- One-off activation fee — €499 excl. VAT
- charged once per company on any plan
- non-recurring
- Annual billing on any plan is presented as two months free compared with paying monthly
Data, GDPR & hosting
A consolidated view of how DIAGIA handles your data.
GDPR overview
GDPR compliance is claimed explicitly and, unusually, backed by specifics. The privacy policy (version 3.2, dated 11 May 2026) sets out a legal basis for each category of data — contract performance, legal obligation, legitimate interest, consent — and lists the seven data-subject rights with their article numbers. A data protection contact is named, legal@diagia.app, with a postal address, a one-month response deadline extendable to three, and the CNIL's full address as the route for complaints. Breach notification within 72 hours is promised. Automated processing is declared to fall outside Article 22 on the grounds that the technician remains the sole decision-maker. Transfers outside the EU rely on Standard Contractual Clauses. No Article 27 representative is designated, which is consistent with a publisher established in France. This remains a self-declaration, not a certification.
Who owns the data?
KORONTIC SYSTEMS owns the platform outright — the algorithms, the automotive knowledge base, the AI system, the interface and the brand — and the terms forbid resale, redistribution, extraction of the knowledge base, reverse engineering and scraping. The diagnostic data you feed in stays yours in practice: the publisher undertakes never to sell it, share it with commercial third parties or use it for advertising. One reservation matters. Resolved diagnoses may be reused, once anonymised and aggregated, to enrich DIAGIA's own knowledge base. The publisher states it does not train AI models for the benefit of third parties, but says nothing about its own models, and offers no way to opt out.
Reuse rights
Within the workshop's own business, reuse is unrestricted: the diagnostic report generated for a job can be exported as a PDF and sent to the vehicle owner, and that is an advertised feature rather than a tolerated one. The garage carries the responsibility for having obtained that owner's consent before entering their email address. Users may also exercise the full set of GDPR rights by writing to legal@diagia.app, including portability in a structured format, and may delete their account either by email or from the app's settings. What the terms explicitly prohibit is any reuse that competes with the publisher: reselling access, making the service available to third parties, extracting the knowledge base, reverse engineering, automated scraping, and reproducing any part of the platform without prior written permission. No commercial licence over the platform's content is granted.
Data retention & training
Hosting summary
The publisher commits repeatedly to hosting within the European Union, on the homepage and again in the privacy policy, and states specifically that registration-plate lookups are cached in an EU database. No individual country is named, only the region. The database, authentication and storage layer is Supabase, described as EU-hosted; the backend API runs on Railway and the website and CDN on Cloudflare. The US addresses shown in the legal notice for Railway, Supabase and Cloudflare are those providers' corporate headquarters, not the declared storage location. Eleven subprocessors are named, among them Stripe, Firebase, Resend, Sentry and PostHog on an EU server — but the AI supplier is deliberately left unnamed as confidential, so the hosting of the model inference itself cannot be established. Transfers outside the EU are covered by Standard Contractual Clauses. The governing law is French and the courts of Paris have exclusive jurisdiction. Stated security measures include TLS 1.2 or above, bcrypt hashing, short-lived JWTs and row-level security.
Where DIAGIA works
Country-level availability.
Available in
Things to keep in mind
Risks and trade-offs to weigh before adopting DIAGIA.
- The twelve-month commitment is firm and the activation fee is non-refundable: at the entry plan the minimum outlay is about €1,700 excluding VAT before you know whether the tool suits your workshop
- Tacit annual renewal punishes forgetfulness — miss the anniversary date and you are committed for another twelve months, with notice accepted only by registered letter or acknowledged email
- The free trial requires a card and converts by default; doing nothing is what triggers the charge, not doing something
- Deskilling is the real cognitive risk: a technician who stops reasoning and simply follows the ranked list still carries sole legal responsibility for the repair, and the publisher's liability is capped at three months of subscription
- The publisher itself warns the models can hallucinate, so any suggestion acted on without verification can put a customer's engine — and your reputation — at risk
- The vehicle owner's email address is entered by the garage, which alone bears the burden of that person's consent, and registration plates are passed to a third-party service and cached
- No opt-out exists from the anonymised reuse of resolved diagnoses, and the PCI-DSS badge shown on the site belongs to Stripe, not to DIAGIA, which holds no security certification of its own
Setup & Integrations
Technical difficulty
Technically undemanding. There is no proprietary hardware, no workshop installation and no integration to configure: any OBD2 scan tool already on the premises will do, and the app installs from the App Store or Google Play, with iOS 15.1 as the minimum. The real friction is administrative rather than technical — signup runs through a four-step form with automatic SIRET verification and a mandatory activity code — plus the manual step of typing in the fault codes and symptoms yourself. The interface is designed for gloved hands and voice dictation is available.
Deployment
Apps stores
Supported languages
Behind DIAGIA
Resources
All the official URLs gathered for verification and reference.
Frequently asked questions
Do I need a specific diagnostic tool to use DIAGIA?
Who is allowed to subscribe?
Which vehicles and brands are covered?
What does it cost, and is there a free plan?
How does the free trial work?
Can I cancel my subscription?
Are my diagnoses confidential, and where is the data stored?
Is my data used to train the AI?
What is a hotline ticket?
Is there an API, and which platforms are supported?
Should you pick DIAGIA?
DIAGIA is a narrow, well-aimed product rather than a general assistant with a car theme. It answers one question a workshop actually loses money on — which fault is it, really — and it answers it with the tooling the shop already has. The supporting documentation is notably better than the norm: a dated and versioned privacy policy, a named list of eleven subprocessors, an EU hosting commitment, and an unusually frank warning that the models can be wrong.
The decisive question is not the technology, it is the contract. Twelve months firm with no early exit, a €499 activation fee excluding VAT, tacit annual renewal, and cancellation valid only by registered letter or acknowledged email. The advertised €99.90 a month is not what the first year costs; at the entry plan the real floor is close to €1,700 excluding VAT, for four diagnoses a month. That is a defensible price if the tool saves the three hours the vendor says a hard diagnosis costs, and a poor one if the shop uses it twice.
Two caveats deserve weight. None of the headline figures — 90% accuracy, 75% time saved, four hours a week — is backed by a published method, the testimonials carry no verifiable business name, and the homepage's own counter of diagnoses performed displays a dash. And KORONTIC SYSTEMS was only entered on the register on 8 June 2026, which is a short track record against which to sign a year.
The 14-day trial is the honest way to find out, provided you diarise the cancellation date. Outside France, or outside the four accepted activity codes, the question does not arise: the door is closed.
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